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TABLEOFCONTENTS

Introduction...............................................................................................................................................................................................................4

EducationalGoalsforElectricity.......................................................................................................................................................................5

MasterMaterialsListforAllLabs.....................................................................................................................................................................6

LabSafety...................................................................................................................................................................................................................8

Section1:StaticElectricity..................................................................................................................................................................................9

Lesson#1:StaticHair..........................................................................................................................................................................................10

Lesson#2:ElectricFields..................................................................................................................................................................................13

Lesson#3:TriboelectricSeries.......................................................................................................................................................................17

Lesson#4:VisibleElectricFields...................................................................................................................................................................21

Lesson#5:Electroscope.....................................................................................................................................................................................24

Lesson#6:ElectrostaticMotor........................................................................................................................................................................26

Lesson#7:AdvancedStaticLab......................................................................................................................................................................28

Lesson#8:AlienDetector..................................................................................................................................................................................33

Lesson#9:CosmicRayDetector.....................................................................................................................................................................36

StaticElectricityEvaluation..............................................................................................................................................................................39

StaticElectricityQuiz...........................................................................................................................................................................................40

StaticElectricityLabPractical.........................................................................................................................................................................43

Section2:Electricity............................................................................................................................................................................................44

Lesson#10:BasicCircuits.................................................................................................................................................................................46

Lesson#11:ConductivityTesters..................................................................................................................................................................49

Lesson#12:Switches&Motors......................................................................................................................................................................52

Lesson#13:DigitalMultimeters.....................................................................................................................................................................57

Lesson#14:MotorSpeedControllers..........................................................................................................................................................61

Lesson#15:ElectricEyeSensor.....................................................................................................................................................................64

Lesson#16:TripWireBurglarAlarm..........................................................................................................................................................67

Lesson#17:PressureSensor...........................................................................................................................................................................69

Lesson#18:LatchingCircuits..........................................................................................................................................................................71

Lesson#19:NerveTester..................................................................................................................................................................................73


ElectricityEvaluation..........................................................................................................................................................................................75

ElectricityQuiz.......................................................................................................................................................................................................76

ElectricityLabPractical......................................................................................................................................................................................78

Section3:Electrochemistry..............................................................................................................................................................................79

Lesson#20:Electrolytes....................................................................................................................................................................................80

Lesson#21:Electrolysis.....................................................................................................................................................................................84

Lesson#22:Electroplating...............................................................................................................................................................................87

Lesson#23:FruitBattery..................................................................................................................................................................................90

Lesson#24:SaltyBattery..................................................................................................................................................................................93

Lesson#25:SilverBattery................................................................................................................................................................................96

Lesson#26:AirBattery......................................................................................................................................................................................98

ElectrochemistryEvaluation.........................................................................................................................................................................100

ElectrochemistryQuiz......................................................................................................................................................................................101

ElectrochemistryLabPractical.....................................................................................................................................................................102

AnswerstoExercisesandQuizzes..............................................................................................................................................................103

VocabularyfortheUnit....................................................................................................................................................................................110


Introduction

GreetingsandwelcometothestudyofElectricity.Thisunitwascreatedbyamechanicalengineer,universityinstructor,airplanepilot,astronomer,robot‐builderandrealrocketscientist…me!IhavethehappyopportunitytoteachyoueverythingIknowaboutelectricityoverthenextsetoflessons.Ipromisetogiveyoumybeststuffsoyoucantakeitandrunwithit…orfly!

Thescientificprincipleswe’regoingtocoverwerefirstdiscoveredbyahostofscientistsinthe19thcentury,eachworkingontheideasfromeachother,mostprominentlyJamesMaxwellandMichaelFaraday.Thisisoneofthemostexcitingareasofscience,becauseitincludesoneofthemostimportantscientificdiscoveriesofalltime:howelectricityandmagnetismareconnected.Beforethisdiscovery,peoplethoughtofelectricityandmagnetismastwoseparatethings.Whenscientistsrealizedthatnotonlyweretheylinkedtogether,butthatonecausestheother,thefieldofphysicsreallytookoff.

Togetthemostoutoftheselabs,therearereallyonlyacoupleofthingstokeepinmind.Sinceweareallheretohavefunandlearnsomethingnew,thisshouldn’tbetoohard.

Oneofthebestthingsyoucandoasthestudentistocultivateyourcuriosityaboutthings.Whydidthatmove?Howdidthatspin?What’sreallygoingonhere?

ThisunitonElectricityischockfullofdemonstrationsandexperimentsfortwobigreasons.First,they’refun.Butmoreimportantly,thereasonwedoexperimentsinscienceistohoneyourobservationalskills.ScienceexperimentsreallyspeakforthemselvesmuchbetterthanIcaneverputintowordsorshowyouonavideo.AndI’mgoingtohityouwithalotofthesesciencedemonstrationsandexperimentstohelpyoudevelopyourobservingtechniques.

Scientistsnotonlylearntoobservewhat’sgoingonintheexperiment,buttheyalsolearnhowtoobservewhattheirexperimentistellingthem,whichisfoundbylookingatyourdata.It’snotenoughtoinventsomenewkindofexperimentifyoudon’tknowhowitwillperformwhentheconditionschangeabit,likeonMars.We’regoingtolearnhowtopredictwhatwethinkwillhappen,designexperimentsthatwilltestthisidea,andlookovertheresultswegottofigureoutwheretogofromthere.Scienceisaprocess,it’sawayofthinking,andwe’regoingtogetplentyofpracticeatit.

Goodluckwiththiselectricityunit!


FortheParent/Teacher:EducationalGoalsforElectricity

Thescientificprincipleswe’regoingtocoverwerefirstdiscoveredbyahostofscientistsinthe19thcentury,eachworkingontheideasfromeachother,mostprominentlyJamesMaxwellandMichaelFaraday.Thisisoneofthemostexcitingareasofscience,becauseitincludesoneofthemostimportantscientificdiscoveriesofalltime:howelectricityandmagnetismareconnected.Beforethisdiscovery,peoplethoughtofelectricityandmagnetismastwoseparatethings.Whenscientistsrealizedthatnotonlyweretheylinkedtogether,butthatonecausestheother,thefieldofphysicsreallytookoff.

Herearethescientificconcepts:

StaticElectricity

Theprotonhasapositivecharge,theneutronhasnocharge,andtheelectronhasanegativecharge.Thesechargesrepelandattractoneanotherkindoflikemagnetsrepelorattract.Likechargesrepel(pushaway)oneanotherandunlikechargesattractoneanother.Generallythingsareneutrallycharged.Theyaren’tverypositiveornegative,ratherhaveabalanceofboth.

Objectsthatareelectricallychargedcancreateatemporarychargeonanotherobject. Thetriboelectricseriesisalistthatranksdifferentmaterialsaccordingtohowtheyloseorgainelectrons.

Electricity

Whenelectriccurrentpassesthroughamaterial,itdoesitbyelectricalconduction. Metalsareconductorsnotbecauseelectricitypassesthroughthem,butbecausetheycontainelectronsthat

canmove.

Electrochemistry

Therearedifferentkindsofconduction,suchasmetallicconduction,whereelectronsflowthroughaconductor(likemetal)andelectrolysis,wherechargedatoms(calledions)flowthroughliquids.

Bytheendofthelabsinthisunit,studentswillbeableto:

Designandbuildsimpleseriesandparallelcircuitsbyusingcomponentssuchaswires,batteries,andbulbs.

Knowhowtodemonstratethatelectricallychargedobjectsattractorrepeleachother. Knowelectricalenergycanbeconvertedtoheat,light,andmotion. Differentiateobservationfrominference(interpretation)andknowscientists’explanationscomepartly

fromwhattheyobserveandpartlyfromhowtheyinterprettheirobservations. Measureandestimatetheweight,length,orvolumeofobjects. Formulateandjustifypredictionsbasedoncause‐and‐effectrelationships. Conductmultipletrialstotestapredictionanddrawconclusionsabouttherelationshipsbetween

predictionsandresults. Constructandinterpretgraphsfrommeasurements.

Followasetofwritteninstructionsforascientificinvestigation.


MasterMaterialsListforAllLabs

Thisisabrieflistofthematerialsthatyouwillneedtodoalloftheactivities,experimentsandprojectsineachsection.Thesetofmaterialslistedbelowisjustforonelabgroup.Ifyouhaveaclassoftenlabgroups,you’llneedtogettensetsofthematerialslistedbelow.Fortenlabgroups,aneasywaytokeeptrackofyourmaterialsistogiveeachgroupanumberfromonetoten,andmakeuptenseparatelabkitsusingsmallplastictubsorbaskets.Putonenumberoneachitemandfilleachtubwiththematerialslistedbelow.Labelthetubswiththesectionname,likeStaticElectricityStudyKitandyouwillhaveaneasywaytokeeptrackofthematerialsandbuildaccountabilityintotheprogramforthekids.Copytheselistsandsticktheminthebinforeasytracking.Feelfreetoreuseitemsbetweenlessonsandunitsections.Mostmaterialsarereusableyearafteryear.MaterialsforStandardLabs

• 9Vbatterywithbatteryclip(RS#270‐325) AAbatteries AAbatterycase(RS#270‐408) Activatedcharcoal(fromafishstore) Alligatorclipwires(RS#278‐1157) Aluminumfoil Bakingsoda Balloon Brassfasteners,8 Bubblesolutionwithwands CdScell(RS#276‐1657) Clockwithsecondhand(orstopwatch) Copperstrips,3 Coppersulfate(www.hometrainingtools.com) Cottoncloth DigitalMultimeter(RS#22‐182orsimilar) Disposablecups Distilledwater Distilledwhitevinegar Drieddill(spice) Dullnail(iron) Freshfruit Glassjar(likeapickleorjamjar)withlid Goggles Graphitefrominsideapencil Hobbymotor,1.5‐3VDC(RS#273‐223) Indexcards Laserpointerorflashlight LED(RS#276‐012) Lemonjuice Longmatch

Packingpeanuts Paperclips Paperconfetti(youcanmakeyourown) Papertowel Pingpongball Plasticgrocerybags Popsiclesticksforstirring Potentiometer(RS#271‐1714) Propellerorpieceoftapeformotorshaft Realsilverware(notstainless) Salt Scissors Shinymetalkey Shinynail(galvanized) Skillet Soap Soupspoon Steelwire(6",likepicturehangingwire) Styrofoamplate Sugar Tape Testtubes,glassorplastic,2

(www.hometrainingtools.com) Thinsponge(about2″square) TuborpieplatetocatchthedripsORasink Unpaintedsteeltacks,2 Vegetableormineraloil Waterbottle Woodclothespin Woodscrew(brass) Woolsweaterorcloth Yardstick Zincstrip(www.hometrainingtools.com)


MaterialsforAdvancedBonusLabs

• 9Vbatteryclip(RS#270‐325)• AAbatteries,4(RS#270‐408)• AAbatterypacks,2(RS#270‐408)• Blackfelt• Dryice• Fishinglineorsewingthread• Flashlight• Foamcup• Foammeattray• FunFlyStickbyUniteachToys

(www.unitechtoys.com/funflystick.html)• Goggles• Heavyglovesforhandlingthedryice• Longstraightpin(longerthanthefilmcans)• Magnet• MPF102(RS#276‐2062)• Neonbulb(RadioShack(RS)#272‐712)• Paperclips• Penny• Relay(RS#275‐206)• Rubbingalcohol• Smallaluminumpietarttins• SmallStyrofoamball• Soupcans• Threefilmcanistersorsmallcontainerswith

tight‐fittinglidsorcorks• Wirecoathanger

LabSafetyGoggles:Theseshouldbewornwhenworkingwithchemicals,heat,fire,orprojectiles.Theseprotectyoureyesfromchemicalsplatter,explosions,andtinyfast‐movingobjectsaimedattheeyes.Ifyouwearglasses,youcanfindgogglesthatfitoverthem.Don’tsubstituteeyeglassesforgoggles,becauseofthelackofsideprotection.Eyeglassesdon’tprovidethisimportantsideeyeprotection.

CleanupMesses:Yourlabareashouldbeneat,organized,andspotlessbeforeyoustart,duringyourexperiment,andwhenyouleave.Scientistswastemoretimehuntingforlostpapers,piecesofanexperiment,andtryingtorepositionsensitiveequipment…allofwhichcouldhaveeasilybeenavoidedhadtheybeentaughtorganizationalskillsfromthestart.

DisposeofPoisons:Ifapoisonoussubstancewasused,created,orproducedduringyourexperiment,youmustfollowtheproperhandlingproceduresfordisposal.You’llfinddetailsforthisintheexperimentsasneeded.

SpecialNotesonBatteries:Donotusealkalinebatterieswithyourexperiments.Findthesuper‐cheapkindofbatteries(usuallylabeled“HeavyDuty”or“SuperHeavyDuty”)becausethesetypesofbatterieshaveacarbon‐zinccore,whichdoesnotcontaintheacidthatalkalinebatterieshave.Thismeanswhenyouwireupcircuitsincorrectly(whichyoushouldexpecttodobecauseyouarelearning),thecircuitswillnotoverheatorleak.Ifyouusealkalinebatteries(likeEnergizerandDuracell)andyourstudentsshortacircuit,theirwiresandcomponentswillgetsuper‐hotandleakacid,whichisverydangerous.

NoEatingorDrinkingintheLab:Allfoodsanddrinksarebannedfromyourclassroomduringscienceexperimentation.Whenyoueatordrink,youruntheveryrealriskofingestingpartofyourexperiment.Forelectricityandmagnetismlabs,alwayswashyourhandsafterthelabisovertorinseofftheleadfromtheelectricalcomponents.

NoHorsePlay:Whenyougoofaround,accidentshappen,whichmeanschemicalsspill,circuitsshort,andallkindsofhazardscanoccurthatyouweren’texpecting.Neverthrowanythingtoanotherpersonandbecarefulwhereyouputyourhands–itcouldbeinthemiddleofasensitiveexperiment,especiallywithmagnetismandelectricity.Youdon’twanttoruntheriskofgettingshockedorelectrifiedwhenit’snotpartofyourexperiment.

Fire:Ifyouthinkthere’safireintheroom(evenifyou’renotsure),letyourteacherknowrightaway.Iftheyarenotaround(theyalwaysshouldbe),smotherthefirewithafireblanketoruseafireextinguisherandsendsomeonetofindanadult.Stop,drop,androll!

Questions:Ifyou’renotsureaboutsomethingstopandask,nomatterwhatit’sabout.Ifyoudon’tknowhowtoproperlyhandleachemical,dopartofanexperiment,ask!Ifyou’renotcomfortabledoingpartoftheexperiment,thendon’tdoit.


Section1:StaticElectricity

Electronsarestrangeandunusuallittlefellows.Strangethingshappenwhentoomanyortoofewofthemgettogether.Somethingsmaybeattractedtootherthingsorsomethingsmaypushotherthingsaway.

Occasionally,youmayseeasparkoflightandhearasound.Thelightandsoundmaybequitesmallormaybeaslargeasaboltoflightning.Whenelectronsgather,strangethingshappen.Thosestrangethingsarestaticelectricity.

Alotoffolksgetnervousaroundelectricity.Youcan'talways”see”what'sgoingon.“WillIgetashockwhenItouchthat?”Manypeoplehaveacertainleveloffeararoundanythingelectricalingeneral.Imean,electronsarereallysmall,andyoucan'tseeelectricitydirectly,butyoucancertainlydetectitseffectswhenyouturnonablender,ringadoorbell,orsetyouralarmclock.

Electricityispredictable,andeverythingwe’reabouttodoiscompletelysafe.Thevoltagesandamperagewe'reworkingwitharewaybelowthe"caution"limit,andthebatterieswerecommendwon'tleakacidorsingefingersifyourstudentsconnectthemthewrongway.(Whichbythewayyoushouldexpectthemtodobecauseit'spartofthelearningprocess.)Iamgoingtohelpyousetupasafelearningenvironmentsoyourkidsarefreetoexperimentwithoutyoulosingsleepoverit.

I'mgoingtowalkyouthrougheverystepoftheway,andbyworkingthroughthediscussionquestions,worksheets,andexercises,you’lllearnnotonlyhowelectricityworks,butalsohowtouseelectricalcomponentslikeswitchesandmotors,dimmersandlightsandalsohowtoconnectthemtogethertobuildusefulthingslikeburglaralarmsandrobots.It'snotenoughjusttolearnabouttheseideas–studentswillgettopracticetheminawaythat'susefulandpractical.That'swhenthelearningreallystickstotheirbrain.


Lesson#1:StaticHairOverview:Greetings,andwelcometothestudyofelectricity!Thisfirstlessonissimplytogetyoutoplaywithstaticelectricityanddecidewhatitisthatyouwanttolearnaboutelectricitysowecandothereallycoolstufflateron.

WhattoLearn:Whenyouaredonetoday,youwillneedtoknowthatelectronsaretoosmallforustoseewithoureyes,butthereareotherwaystodetectsomething’sgoingon.You’llalsogettolearnthatinsidetheatom,theprotonhasapositivecharge,andtheelectronhasanegativecharge.Bydoingyourexperiments,you’lldiscoverhowlikechargesrepelandoppositechargesattracteachother.

Materials

1balloon Clockwithsecondhand(orstopwatch)

LabTime

1. Blowupyourballoonandtieitoff(ifthisisn’talreadydoneforyou.)2. Scrubyournearestlabpartner’sheadwiththeballoonuntilyoucangetittostandup.Ifitdoesn’twork,try

anotherlabpartner.3. Afterafewlaughs,lookaroundtheroomandfindeightthingstotrystickingyourchargedballoonto.Write

themdownonyourworksheetunder“Item/Object”beforeyoustart.You’llfindyourworksheetonthenextpage.

4. Important:Findthebestlabpartnerheadtouseduringtheentireexperimentthatyoucollectdatafor.Besuretochargeyourballoonthesamewaybeforetestingeachobject.Thismeansyouusethesamenumberofrubsonthesameheadforalltenitems.Starttimingassoonastheballoonstickstoyourchosenobject.


StaticElectricity:BalloonExperiment

Item/Object DidItStick? HowLongDidItStick?(measureinseconds)

NameofHeadUsedforExperiment____________________________________________________________________________________

LabPartners______________________________________________________________________________________________________________

Reading

Electronsarestrangeandunusuallittlefellows.Strangethingshappenwhentoomanyortoofewofthemgettogether.Somethingsmaybeattractedtootherthingsorsomethingsmaypushotherthingsaway.Occasionallyyoumayseeasparkoflightandhearasound.Thelightandsoundmaybequitesmallormaybeaslargeasaboltoflightning.Whenelectronsgather,strangethingshappen.Thosestrangethingsarestaticelectricity.

Differentpartsoftheatomhavedifferentelectricalcharges.Theprotonhasapositivecharge,theneutronhasnocharge(neutron,neutralgetit?)andtheelectronhasanegativecharge.

Thesechargesrepelandattractoneanotherkindoflikemagnetsrepelorattract.Likechargesrepel(pushaway)oneanotherandunlikechargesattractoneanother.Soiftwoitemsthatarebothnegativelychargedgetclosetooneanother,thetwoitemswilltrytogetawayfromoneanother.Iftwoitemsarebothpositivelycharged,theywilltrytogetawayfromoneanother.Ifoneitemispositiveandtheothernegative,theywilltrytocometogether.

Blowupaballoon.Ifyourubaballoononyourhead,theballoonisnowfilledupwithextraelectrons,andnowhasanegativecharge.Trythefollowingexperimenttocreateatemporarychargeonawall:Bringtheballoonclosetothewalluntilitsticks.


Oppositechargesattract,right?So,istheentirewallnowanoppositechargefromtheballoon?No.Infact,thewallisnotchargedatall.Itisneutral.Sowhydidtheballoonsticktoit?

Theballoonisnegativelycharged.Itcreatedatemporarypositivechargewhenitgotclosetothewall.Astheballoongetsclosertothewall,itrepelstheelectronsinthewall.Thenegativelychargedelectronsinthewallarerepelledfromthenegativelychargedelectronsintheballoon.

Sincetheelectronsarerepelled,whatisleftbehind?Positivecharges.Thesectionofwallthathashaditselectronsrepelledisnowleftpositivelycharged.Thenegativelychargedballoonwillnow“stick”tothepositivelychargedwall.Thewallistemporarilychargedbecauseonceyoumovetheballoonaway,theelectronswillgobacktowheretheywereandtherewillnolongerbeachargeonthatpartofthewall.

Thisiswhyplasticwrap,Styrofoampackingpopcorn,andsocksrightoutofthedryersticktothings.Allthosethingshavechargesandcancreatetemporarychargesonthingstheygetcloseto.

Exercises

1. Whydoesthehairsticktotheballoon?

2. Howdoyougetridofelectrons?

3. Canyouseeelectrons?Whyorwhynot?

4. Doesitmatterwhatkindofhairyourubtheballoonon?

5. Howlongdoesthehaircontinuetostandupafteryouremovetheballoon?

6. Doesitmatterwhatkindofballoonyouuse?

7. Howfastorslowdoyouneedtorubforthebiggestchargeontheballoon?

8. Doeshaircolormatter?

9. Thisevening,findanarticleorstorythatdescribeshowelectricityimprovesourlives.Bringthearticletoschool.Ifyoubringinanarticlethatnooneelsebringsin,yougetextrapoints.


Lesson#2:ElectricFieldsOverview:Didyouknowthatyoucanmakethingsmoveusingstaticelectricity?You’regoingtobeadetectiveandfigureouthowdifferentobjectsinteractwhenyousticktheminanelectricfield.

WhattoLearn:We’regoingtousetheconceptthatlikechargesrepel(thinktwoelectrons,ortwominuscharges)andoppositechargesattract(thinkplusandminus).You’realsogoingtoplaywiththeideaofaforcefield,whichcanpullanobjecttowardsitorpushanobjectaway.Aforcefieldisaninvisibleareaaroundanobjectwithinwhichthatobjectcancauseotherobjectstomove.

Materials

7‐9”latexballoon Onefullwaterbottle Onetuborpieplatetocatchthedrips Pingpongball Bubblesolutionwithwandsforblowingbubbles 10packingpeanuts Woolclothorsweater Paperconfetti

LabTime

1. Chargeyourballoonbyrubbingitonyourheadvigorously.

2. TheWigglyWater:Invertthefullwaterbottleoverthepieplate,holdingitagood1‐2feetabovetheplatesothatathinstreamflowsoutfromthebottletothepieplate.(Note:Ifyou’reusingasinkinstead,putthewateronthelowestsettingsoathinstreamtricklesout.)Chargetheballoononyourheadandbringitclosetothewaterstream–canyoumakeitwiggle?

a. Whichwaydoesthestreamofwaterbend,toward(attracted)orawayfrom(repelled)theballoon?

b. Howmuchwaterworksbestforthisexperiment:slow,mediumorfaststream?

3. PaperHoppers:Chargetheballoononyourheadagain.Bringthechargedballoonclosetoapileofconfetti.Canyoupickupalltheconfetti?

a. Howlongdoesittakebeforetheconfettijumpsofftheballoon?

b. Doesthisexperimentworkiftheballoonisnotchargedfirst?


4. DancingBubbles:Chargetheballoononyourheadagainwhileyourlabpartnerblowsbubblesaboutthesizeofyourfistusingthebubblesolutionandwand.Bringthechargedballoonclosetoafloatingbubbleslowly.

a. Isthebubbleattractedtoorrepelledfromtheballoon?

b. Howlongcanyoukeepthebubbleinteractingwiththeballoon?

c. Ifyoukeepabubbleonthewandandthenbringthechargedballoonclosetoit,canyoudistortthebubble’sshape,orevenpullitoffthewand?

5. ChasingBalls:Bringthechargedballoonclosetoarestingpingpongballslowly.Makesuretodothisona

smoothandlevelsurface,wheretheballhasroomtomovearound.You’llneedagoodchargeontheballoontomakethisoneworkwell.

a. Isthepingpongballattractedtoorrepelledfromtheballoon?

b. Whatisthechargeontheballoon?

c. Whatisthechargeonthefarsideofthepingpongball?

6. GhostPoop:Rubapackingpeanutwithapieceofwoolandstickthemtothewalloryourlabpartner’s

back.

a. Howmanydifferentsurfacescanholdghostpoop?Namethem:


Reading

Thefourforcefieldsaregravity,magnetic,electric,andelectromagnetic.We’regoingtoinvestigatetheelectromagneticforcefieldandhowtocreatechargeimbalancestomakethingsstick,wiggle,dance,andmove.

Forcefieldsaren’tjustsomethingforsciencefictionwriters.Theyareactuallyaveryrealandverymysteriouspartoftheworldinwhichyoulive.So,whatisaforcefield?Well,Ican’ttellyou.Tobehonest,nobodycan.

There’squiteabitthatisstillunknownabouthowtheywork.Aforcefieldisastrangeareathatsurroundsanobject.Thatfieldcanpushorpullotherobjectsthatwanderintoitsarea.Forcefieldscanbeextremelytinyorlargerthanoursolarsystem.

Awaytopictureaforcefieldistoimagineaninvisiblebubblethatsurroundsagizmo.Ifsomeotherobjectentersthatbubble,thatobjectwillbepushedorpulledbyaninvisibleforcethatiscausedbythegizmo.That’sprettybizarretothinkabout,isn’tit?However,ithappensallthetime.

Asyousitthererightnow,youareengulfedinatleasttwohugeforcefields,theEarth’smagneticfieldandtheEarth’sgravitationalfield.Today,we’regoingtolearnabouttheelectricfield.

Anelectricfieldisthespacearoundanelectrically‐chargedparticle(thinkelectron).ThisideawasfirstintroducedbyMichaelFaraday.It’sdefinedastheelectricforceyoufeel,andthedirectionofthefieldistakentobethedirectionoftheforcethefieldexertsifyoustickapositivechargeinthefield.

Howdothingsgetcharged?Generallythingsareneutrallycharged.Theyaren’tverypositiveornegative.However,occasionally(oronpurposeaswe’llseelater)thingscangainacharge.Thingsgetchargedwhenelectronsmove.Electronsarenegatively‐chargedparticles.Soifanobjecthasmoreelectronsthanitusuallydoes,thatobjectwouldhaveanegativecharge.

Ifanobjecthaslesselectronsthanprotons(positivecharges),itwouldhaveapositivecharge.Howdoelectronsmove?Itturnsoutthatelectronscanbekindoflooseygoosey.Dependingonthetypeofatomtheyareapartof,theyarequitewillingtojumpshipandgosomewhereelse.Thewaytogetthemtojumpshipistorubthingstogether.

Remember,instaticelectricity,electronsarenegativelychargedandtheycanmovefromoneobjecttoanother.Thismovementofelectronscancreateapositivecharge(ifsomethinghastoofewelectrons)oranegativecharge(ifsomethinghastoomanyelectrons).Itturnsoutthatelectronswillalsomovearoundinsideanobjectwithoutnecessarilyleavingtheobject.Whenthishappenstheobjectissaidtohaveatemporarycharge.

Whenyourubtheballoononyourhead,you’restealingelectronsfromyourscalp,creatingatemporarypositivechargeonyourhead,andatemporarynegativechargeontheballoon.Whenyoubringthenegativelychargedballoonclosetosomethingthathasabalanceofcharges,likeapingpongball,theelectronsrepelandmovetotheoppositesideoftheball,leavingthepositivechargestoattracttowardtheballoon,sotheballrollstowardtheballoon.Theelectricchargeontheballooncanattractallsortsofinterestingthings,likepaperstrips,pencilshavings,soapbubbles,packingpeanuts,andtissuepaper.Remember,thepositiveparticlesmoveupandaredrawntowardthenegatively‐chargedballoon,whichiswherethemovementcomesfrom.

Whataboutwater?Waterislikeabarmagnetinthattherearepolesonawatermolecule:there’saplussideandaminusside,andthewatermoleculeslineuptheirpositiveendstowardtheballoonwhenyoubringitclose.Kidsaregoingtoholdthechargedballoonnearathinstreamofwatertoseeiftheycanmakethewaterwigglewithouttouchingit.Thebottomline?Thechargedballoonattractsthestreamofwater.


Exercises

1. Whydidthepingpongballmove?

2. Whydidthepaperjumpup?

3. Doesthepapersticktotheballoonforever?Whyorwhynot?

4. Whatmadethewatermove?

5. Doesitmatterifthewaterishotorcold?

6. Whatotherliquidsdoyouthinkwouldworkbesideswater?

7. Doesitworkwithafullstreamofrushingwater?Apanfullofwater?Whyorwhynot?

8. Whichway(attractedorrepelled)didthesoapbubblemove?

9. Whatholdsthepackingpeanuttothewall?

10. Dotheseexperimentsworkifit’sraining?Whyorwhynot?

11. Whatifyougettheballoonwetfirstandthentrytheseexperimentsagain?

12. Doesthepapersticktotheballoonlongerthanthepackingpeanutssticktothewall?


Lesson#3:TriboelectricSeriesOverview:Todayyouaregoingtotakeasecondlookatstaticcharge,exactlyhowitbuildsup,andwhichwaytheelectronsmovewhenmaterialsarerubbedtogether.

WhattoLearn:Whenyoufinishtoday,youwillneedtoknowhowastaticchargeiscreatedandhowtotellifit’sapositiveornegativechargethatyou’vebuiltup.Sinceyoualreadyknowthehair‐balloonexperimentbuildsupanegativecharge,youcanusethistohelpyoufigureitout.ScientistsdothisexperimenttocreatetheTriboelectricSeries,achartthatlistshowtheelectronstendtomove,whethertoorfromthematerial.

Materials

Styrofoamplate Woolsweaterorcloth 2plasticbags(clearplasticgrocerybagsworkwell) Cottoncloth Formicatableorcountertoporscrappiece 7‐9”latexballoon Scissors Tape

LabTime

1. HandyStatic:Cuttwo1”x10”stripsfromaplasticgrocerybag.Holdthestripfirmlyatoneendandgrasptheplasticwithyourotherhandbetweenyourthumbandfingers.Workingquickly,pullyourhandsothattheplasticrunsthroughyourfingers.Repeatseveraltimestobuildupalargechargeonthestrip,leavingithangingdownwhenyou’redone.

a. Placeyourhandnearthestripandobservewhathappens:

b. Namethreeobjectsthatthestripisattractedto.Areanyofthesechargedoraretheyneutral?

c. Havealabpartnerchargeasecondstripwhileyourechargethefirstandobservewhathappenswhenyoubringthetwochargedstripsclosetogether.


1. IdentifyingFlyingObjects:We’regoingtotakeadvantageofthisideaaboutrepulsiveforcesbymakingaflyingobject.

a. Cutoutatwo‐inchsectionofthegrocerybag.Thiscanbeinaringshape,glidershape,oranythingyouwant.Justbesureyouhaveasmallpieceandnotthewholebag.Also‐theinkfromtheprintingonthebagcanpossiblyaffectthewaythebagchargesup,sopickablankspottocutfrom.

b. Blowuptheirballoonandtieitoff.c. Testoutyourlabpartnerstofindoutwhocangivetheballoonthebestcharge.d. Asecondlabpartnerisgoingtochargeupthegrocerybagscraponadesklikethis:placethebagon

theFormicacounter/deskandrubitwithacottoncloth.(Ifyou’reshortoncloths,useaT‐shirt.)e. Canyoukeepthebagpiecefloatingabovetheballoon?Forhowlong?

Optional:Ifyouwanttoupgradetoaglidershape,here’showyoudoit:i. Cuta3.5”squarefromtheplasticgrocerybagii. Foldinhalfiii. Placeasmallpieceoftapeononeoftheopenendsadjacenttothefold,startingfromthe

foldandtapeuponlyhalfway.iv. Chargeitupthesamewayasyoudidwiththeplasticbagandseeifyoucangetittofly!

f. Nowlet’sseeifthere’sadifferenceinthewaywechargethingsup.Grabafoamplateandrubit

withwool.Usethechargedfoamplateinsteadoftheballoon.Whathappened?

g. Chargethefoamplatewithaplasticbag,andtryflyingyourobject.Whathappened?

h. Tryrubbingotherobjectsandfilloutthetableonthenextpage.Youcantrycharginguptheglider,balloon,orfoamplatedifferently…it’suptoyou.


IdentifyingFlyingObjectsDateTable

ItemsRubbedTogether Whatdidyouobserve?Wasthechargepositiveornegative?

CottonandPlasticBag Floatedabovenegatively‐chargedballoon negative

BalloonandHair Gliderfloatedaboveballoon negative

PlasticBagandFoamPlate

WoolandFoamPlate

Reading

Ifyourubaballoonalloveryourhair,theTriboelectricEffectcausestheelectronstomovefromyourheadtotheballoon.Butwhydon’ttheelectronsgofromtheballoontoyourhead?Thedirectionofelectrontransferhastodowiththepropertiesofthematerialitself.Andtheballoon‐haircombinationisn’ttheonlygameintown.

TheTriboelectricSeriesisalistthatranksdifferentmaterialsaccordingtohowtheyloseorgainelectrons.Arubberrodrubbedwithwoolproducesanegativechargeontherod:however,anacrylicrodrubbedwithsilkcreatesapositivechargeontherod.Afoamplateoftenhasapositivechargewhenyouslideoneoffthestack,butifyourubitwithwoolitwillbuildupanegativecharge.

Nearthetopofthelistarematerialsthattakeonapositivecharge,suchasair,humanskin,glass,rabbitfur,humanhair,wool,silk,andaluminum.Nearthebottomofthelistarematerialsthattakeonanegativecharge,suchasamber,rubberballoons,copper,brass,gold,cellophanetape,Teflon,andsiliconerubber.Scientistsdevelopedthislistbydoingaseriesofexperiments,verysimilartotheoneswe’reaboutto.


Exercises

1. Whathappenedtothestripofplasticafteryouranitthroughyourfingers?

2. Isthestripattractedtoneutralobjects?Whyorwhynot?

3. Whathappensifyouchargetwoplasticstrips–aretheyattractedorrepelledfromeachother?

4. Howlongdidyoukeepthebagfloatingabovetheballoon?

5. Whydidtheplasticbagpiecefloatabovetheballoon?

6. Whatwasthedifferencewhenyourubbedthefoamplatewithwoolversuswithabag?

7. Whichcombinationgavethebestresultsforkeepingyourglideraloft?

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ChargedObjectAppliedtoWire#1

ChargedObjectAppliedtoWire#2

Observation(Whatdidtheseedsdo?)

Balloon‐Hair,

NegativeCharge

Nothing Seedsrotatedandmovedtowardballoon.

9. Drawapictureofyourbestexperimentrunthatshowstheelectricfield:

Reading

Thedillleavesareallshapedlikerods,whichmovetolineupinthefield(whichiswhyroundparticleslikecinnamonandpepperdon'tworkaswell).Thedillhasabalanceofcharges,meaningthatthere’sanequalamountofbothplusandminuscharges.

Whenyoubringachargedobjectlikeanegativelychargedballoonupclose,thenegativechargesinthedillarerepelledandpushedawaywhilethepositivechargesinthedillareattractedtotheballoon,soonesideofthedillbecomesminusandtheotherplus.Sincethedillisfreetomoveintheliquid,thedilllinesitselfupintheelectricfieldtoindicatethechargedirection.Thepositiveendofthedilllinesuptopointatthenegativelychargedballoon.

Note:Ifyourdillisn'tmovingatall,yourobjectmaynothaveachargeonit.Thiscanhappensimplybytouchingtheobjectwithyourfingers(thelittlebitofoilfromyourfingersisenoughtokeepachargefrombuildingup).Orif


ithasrecentlyrained,orifyouliveinanareaofhighhumidity,oryourobjectleakschargeinanynumberofotherways.Youcantrytoincreaseyourchancesofgettingastaticchargebycleaningitwithrubbingalcoholafteryouusesoapandwateranddryingitoutcompletely,andyoushouldseebetterresults.

Exercises

1. Whathappenedwhenyoubroughtachargedballoonnearthedill?

2. Whatsideofthedillwasattractedtotheballoon?

3. Whathappenedwhenyoubroughttwonegativechargesnearthedill?

4. Wereyouabletomakethedillcomeoutoftheliquidandontotheballoonwithouttouchingtheoil?


Lesson#5:ElectroscopeOverview:Learnhowtobuildasimpleinstrumentfordetectingelectrostaticcharge,eitherpositiveornegative,soyou’llalwayshaveawaytoknowifyou’reinanelectricfield.

WhattoLearn:WhenhighenergyradiationstrikestheEarthfromspace,it’scalledcosmicrays.Tobeaccurate,acosmicrayisnotlikearayofsunshine,butratherisasuper‐fastparticleslingingthroughspace.Thinkofthrowingagrainofsandata100mph…andthat’swhatwecalla‘cosmicray’.Buildyourownelectroscopewiththisvideo!

Materials

1largepaperclip 1pieceofaluminumfoil Tape Indexcard Smallglassjar(likeapickleorjamjar)withlid 1balloonand/orotheritemstobuildupastaticchargefrompreviouslessons Scissors

LabTime

1. Takefoilandcuta½”strip.Folditinhalfandsnipthecornersonbothsidesofthefold.Flattenwell.2. OpenthepapercliptomakeanL‐shapewithasmallhookontheend(tokeepthefoilfromslidingoff).3. Tracetheopeningofthejarontotheindexcardandcutoutthecircle,makingitasmidgelargerthanthejar

(soitdoesn’tfallinwhenplacedontop).Pokeaholeinthecenterwiththepaperclip.4. DrapethefoilstripovertheshortendoftheL‐shape.5. InsertthelongendoftheL‐shapeupthroughtheholeintheindexcard.6. Tapetheindexcardtothejaropening,foilleavesdanglinginside,nottouchingthebottomorsidesofthe

jar.7. Wadupalooseballoffoilandstickitontheendofthepaperclipthatispokingoutofthetop.

8. Howwillyoutestyourelectroscope?Explain:

9. Howwillyoudischargeyourelectroscope?


ElectroscopeDataSheet

StaticChargeSource Whatdidyouobservewiththeelectroscope?

Hair‐Balloon

ReadingThisdeviceisknownasanelectroscope,anditsjobistodetectstaticcharges,whetherpositiveornegative.Whenastaticchargeisbroughtclosetothefoilball,theconnectedfoilstrips(“leaves”)spreadapartbecauselikerepelslikecharges.

Theeasiestwaytomakesureyourelectroscopeisworkingistorubyourheadwithaballoonandbringitnearthefoilballontop–thefoil“leaves”insidethejarshouldspreadapartintoaV‐shape.

Ifthisdoesn’thappen(noV‐shape),hereareafewthingstocheckinto:Itmaybetoohumidofaday(closeyourwindowsandcrankontheheat),there’snotagoodelectricalconnectionbetweenthefoilballandthefoilleaves,orsometimesusingametallidcausesthechargetodissipatetooquickly(useacorkandstickyourwirethrough,ortapeanindexcardoverthemouthofthejarandgluethewiretothecard).

Exercises

1. Whydothefoilstripsspreadapart?

2. Howdoyoudischargetheelectroscope?

3. Whydidweuseaglassjar?

4. Doestheelectroscopereactthesamewaywhetherit’sexposedtoapositiveornegativecharge?

5. Listfourwaystochargetheelectroscope.


Lesson#6:ElectrostaticMotorOverview:Didyouknowthatyoucanmakeamotorturnusingstaticelectricity?We’regoingtousetheconceptthatlikechargesrepel(thinktwoelectrons)andoppositechargesattract.

WhattoLearn:Howtomakeanelectrostaticmotorusingtheideasofplusandminuschargestoattractandrepulseachargedobject.

Materials

Balloon(oneperstudent) Soupspoon Flattable Yardstick

LabTime

1. Setthespoonface‐downonthetable,neartheedge.2. Carefullybalancetheyardstickonthebackofthespoon.Youwanttheyardsticktobeperfectlybalanced

andnottouchingthetableorfallingofftheedge.3. Blowuptheballoon.4. Chargetheballoonbyscrubbingitonyourhead.5. Bringtheballoonneartheedgeoftheyardstickthat’shangingoffthetable.Theyardstickshouldbeginto

chasetheballoon.6. Canyoupositionyourlabteamaroundtheperimetertoseehowfastyoucanmakeyouryardstickgo?

Drawadiagramofyourexperimentandlabeleachstudentparticipating.

7. Whatwouldhappenifyouusebothapositivelychargedobjectandanegativelychargedobjecttomaketheyardstickmove?


Reading

ThefirstelectrostaticmotorsweredesignedandtestedbyBenjaminFranklinandAndrewGordoninthe1750s.Anelectrostaticmotorisbasedonelectriccharge,likewe’vebeenstudying.It’sdependentontheattractionofplus‐minusandtherepulsionofminus‐minusand/orplus‐plusinordertowork.Electrostaticmotorsthatyoufindontheshelftodayusuallyrequirehighvoltage,sothisexperimentisaperfectdemonstrationofhowitworkswithoutthekidsgettingshocked.Thesetypesofmotorsarefoundintinyelectronicsystemsthatarewaytoosmallforordinarymagneticmotorstobeusedin.

Exercises

1. Whathappensifyourubtheballoononotherthings,likeawoolsweater?

2. Ifyoupositionotherpeoplewithchargedballoonsaroundthetable,howlongcanyoukeeptheyardstickgoing?

3. Canweseeelectrons?

4. Howdoyougetridofextraelectrons?

5. Whydoyouthinktheyardstickmoved?

6. Whatwouldhappenifyouusebothapositivelychargedobjectandanegativelychargedobjecttomaketheyardstickmove?


Lesson#7:AdvancedStaticLabOverview:Todayisthedaywepullallthepiecesthatwe’vebeentalkingabouttogethertomakeareallyneatelectrostaticlab.You’regoingtodiscoverhowanelectrostaticmotorcanreallyspinfastbyusingbothplusandminuscharges,howtocreateachargedifferencetoringFranklinbells,makepieplatesfly,andhowtolightupabulbwithoutusingbatteries.

WhattoLearn:Payspecialattentiontoseehowadifferenceinchargecanmakethingsmove,roll,spin,chime,fly,lightup,androtate.Plusandminuschargescanbeusedasapush‐pullforcethatworkstogetherintandem.

Materials

sheetofpaper twoempty,cleansteelsoupcans aluminumfoil neonbulb smallfoilballwithfishinglineorsewingthreadattached foamcup dozensmallaluminumpietarttins foammeattrayorslabofStyrofoam FunFlyStick(alsocalled“WonderFlyStick”)ORaballoonandonepieceofshapedtinsel

Optional:ElectrostaticMotorIfyou’remakingtheelectrostaticmotor,you’llalsoneed:

threefilmcanistersorM&Mcontainers longstraightpin penny 2paperclips hotgluegunwithgluesticks drillwithsmalldrillbit scissors tape

LabTime

1. GrabyourFlyStickandmakeyourtinselfloat.Doesthisremindyouanyexperimentswe’vedonebefore?Whichexperiment(s)?

2. Setthemeattrayupside‐downonyourtable.Thiswillprovideaninsulatinglayerforthestaticchargeswhileyouwork.


3. FlyingPans:InverttheStyrofoamcuponthemeattray,open‐enddown.Setastackofpietartpansonthe

bottomofthecup.GentlytouchtheFlySticktothepiepansandpressthebutton.Ta‐daa!

a. Whydidthepansflyoffthecup?

b. WheredoestheFlyStickneedtobeforthisexperimenttowork?

c. DoestheFlyStickhavetotouchthepansforthepanstomove?

4. NeonBulb:Haveonestudentholdoneofthewiresofaneonbulb(picturedleft)inonehand.AnotherstudentbringstheFlyStickupclosetotheotherwireandactivatesthewand.

a. Whathappened?

b. Whatifyoudon’tholdthewire?Doesthischangehowitworks?

c. What’sinsidethebulb?

d. Whydoestheneonbulblightup?


5. FranklinBell:Settwoclean,steelsoupcanswiththeirbottomsaboutaninchapartonthemeattray.HoldthefoamballbetweenthecansandhaveanotherstudenttouchoneofthecanswiththeFlyStick.

a. Whathappened?

b. Isthereaspecialspottoholdtheballand/orFlyStick?Ifso,where?

c. Whathappensifyouplaceyourhandonthemetalpartoftheothercanduringyourexperiment?

d. Whydoesholdingyourhandonthecandothattotheexperiment?

6. WallPaper:Putasheetofpaperonthewall,andrunyourFlyStickoverthesurfaceacoupleoftimes,thenremoveit.

a. Whathappened?

b. Whydoesthepaperdothat?

c. Filloutthedatatable:


StaticElectricityLabDataSheet

TrialNumber

Howlongdidyouchargethepaperfor? Howlongdidthepapersticktothewall?

1

2

3

4

5

7. Optional:ElectrostaticMotorBuildSteps:a. Placethreefilmcanistersonthemeattrayinaline,aboutahalfinchapart.Makesmallmarkson

thetraysoyouknowwheretheyneedtobespacedwhenyougluethem.b. Gluethetopsofthetwoouterfilmcansdownontothemeattray.Donotgluethefilmcanisterbody

tothetops.c. Wrapthebodyofafilmcanwithaluminumfoilusinghotgluetosecureintoplace(nottape).Open

upone‐halfofapaperclipandtapeittothesidethefilmcanisteryoucoveredwithfoil.Makesurethemetalpaperclipistouchingthemetalfoil.Makeasmallhookattheendofthepaperclipforthechargetobuildupon.Repeatwithasecondfilmcanister.

d. Hotgluethepin,pointy‐sideupinthemeattrayatthemiddlefilmcanposition.e. Drillasmallholeinthebottomofthethirdfilmcanisterandsetitright‐sideupontothepin.Make

sureitslidesfreelyontothepin.f. Nowglueapennyinsidethelidanddrillaholehalfwaythroughthepenny.Thetipofthepinshould

restintheholewhenassembled.g. Wrapthethirdfilmcanwithfoil,gluingsparinglyintoplace.Makethreecuts(asshowninvideo)

andfoldthefoilbackalittlebitsotherearethreefoilsectionsnotincontactwitheachother.Youwantthreeisolatedfoilareasforittoworkright.

h. Snaponlidofthirdcanisterandslideitonthepin,centeringthepinintheholeinthepenny.Spinitwithyourfingersandmakesurethere’slittletonofriction.Iftherotordoesn’tturnfreely,addatinydropofoilonthepennyand/oratthebottomhole.

i. Toactivate,touchtheFlySticktooneofthestators(stationaryfilmcanisterwiththepaperclipattached)andtouchyourfingertotheother.Therotorwillstarttoturn.


Reading

HoldaFlyStickinyourhandandwaveitaround,Withyourotherhand,holdapieceoftinsel(whichcomeswiththeFlyStick)anddropitovertheFlyStickasyoupressthebutton.Thetinselshouldfalluneventfullyuntilithitsthewand’selectricalfield,andthenPOOF!itpuffsintoshape.What’sgoingon?

Stoppressingthebuttonandwatchhowthetinselstillreactswiththewand.Playaroundwiththetinselpiecesforabituntilyougetonestucktotheceiling.Chargeanotherpieceoftinselandpointouthowyouarechasingthetinsel.Whatchargeisonthetinsel?WhatchargeisontheFlyStick?

Flipthewandaroundandpointthebuttendofthestickatthetinsel,andcanyounoticehowthetinselchasesyou?Whatchargeisonthebottomendofthewand?

TheFlyStickislikeaBIGchargedballoon,whichalsochargesthetinselwiththesamenegativecharge.Likerepelslikecharges,sothetinseltriestogetasfarawayfromitselfaspossible,justliketheleavesfromtheelectroscope.Thetinselstickstotheceilingforthesamereasontheghostpoopstuck‐thenegativechargesinthetinselrepelthewall’selectrons,leavingthepositiveprotonstobeattractedtothetinsel.

Exercises

1. Whatiscommonthroughoutalltheseexperimentsthatmakethemwork?

2. Whatmakestheneonbulblightup?Whatelsewouldworkbesidesaneonbulb?

3. Doesitmatterhowfarapartthesoupcansare?

4. Whydoesthefoilballgobackandforthbetweenthetwocans?

5. WhydothepanstakeonthesamechargeastheFlyStick?

6. Whenstickingasheetofpapertothewall,doesitmatterhowlongyouchargethepaperfor?

7. Drawadiagramtoexplainhowtheelectrostaticmotorworks.Labeleachpartandshowwherethechargesareandhowtheymaketherotorturn.


Lesson#8:AlienDetectorOverview:Thisexperimentisforadvancedstudents.Thissimplecircuitcandetectelectricfields.Remembertheelectroscopeexperiment?Thisisanelectronicversionofit!Afteryou’vebuildone,handittoyourfriendsandannouncethatyou’vejustbeentoldthere’sanalienpresenceintheroom,andchallengethemtotrytofigureoutwherethealiensarehiding.(Letthemknowthataliens,likekids,neverstayinoneplaceeither.)

WhattoLearn:Thisdetectorfindsareasofpositivecharge,andissosensitivethatyoucangoaroundyourhouseanddiscoverpocketsofstaticcharge…evenfromyourownfootprints!

Materials

9Vbattery 9Vbatteryclipwithtwowires(RadioShackpart#270‐325) MPF102(RadioShackpart#276‐2062) LED(anyregularLEDworksfine,orRadioShackpart#276‐012isagreatchoice,becauseitwilllightupin

bothdirectionsincasethekidshookitupbackwards) 3alligatorclipleads(RadioShackPart#278‐1156)

LabTime

1. HoldtheMPF102transistor(imageatleft)withtheflatsidefacingyou.Beverycarefulwiththese,asit’seasytosnapoffthelittlewires,orzapthemwithtoomuchheatorstaticwhichkillsthem.Here’showyouidentifytheparts:

a. Pin#1istheoneontheleft,alsocalledtheemitterordrain.b. Pin#2isinthemiddle,calledthebaseorsource.c. Pin#3isontherightside,calledthecollector,orgate.

2. GentlyspreadapartthethreeleadsintoaW‐shape,soyoucangetintherewithalligatorclips.

3. Bendthegate(pin#3ontherightside)upward.Thisisgoingtobeyourantenna,andwillnotbeconnectedtoanything.Youcansolderalongerwireifyou’remountingitinasoapboxifneeded.

4. Connectthesource(middlelead)toanalligatorcliplead.Theotherendofyouralligatorwireconnectstothepositive(red)wireofthebatteryclip.

5. SeparatethetwowiresontheLEDintoaVshapesoyoucansliponalligatorclipleadswithoutthemtouchingeachother.

6. Connectthedrain(pin#1ontheleftside)tooneoftheLEDwiresusingasecondalligatorclipwire.7. Usingthethirdalligatorcliplead,connecttheotherLEDwiretotheblackwireonthebatteryclip.Make

surethealligatorclipleadisconnectedtothemetal,nottheinsulationpartofthewire.It’seasytohaveitconnectedonthelastbitoftheinsulation,whichraisesitupalittleanddoesn’tmakemetal‐to‐metalcontactbetweenthealligatorjawsandthewire.Takeyourtimeanddoitright.

8. Checkallconnectionstwicebyrepeatingsteps#1‐9.Double‐checkbeforepoweringup.9. Carefullyinsertthe9Vbatteryintothebatteryclip.TheLEDshouldlightup.10. IftheLEDisdark,tryrunningaplasticpenthroughyourhairandwavingthepenattheantennagently.

TheLEDshouldlightup.


11. Donottouchtheantenna!Thiswillzapthecircuitandfrythetransistor,andthenyouwillhavetostartallover.Youcanincreasetheantennasensitivitybydanglinganextrawire(likeanalligatorcliplead)totheendoftheantenna.

12. Nowwalkaroundtheroomandfindthosealiens!Andthenfillouttheworksheet.

Ifthedetectordoesn’twork:

1. Ifitdoesn’twork,switchbatterieswithsomeonetoseeifyou’vegotagoodpowersource.Itdoesn’ttakemuchtopowerthiscircuit.

2. Ifitstilldoesn’twork,disconnecteverythingandstartover!Youmighthavesomethingnotconnectedright.3. Ifitstilldoesn’twork,switchoutyouralligatorwiresfornewones.Sometimesthere’sabreakbetweenthe

wireandthealligatorhead,whichbreaksthecircuitopen.4. Ifyou’restillreadingthis,myguessisthatitSTILLdoesn’twork…whichmeansacoupleofthings:

a. It’stoohumid.Ifyoucan’tgetaballoontomakeyourarmhairstandup,it’stoohumidforthisexperiment.You’llhavetotrythisonanotherday,orclosethedoorsandcrankontheheat.

b. Transistorisconnectedwrong,sogothroughsteps#1‐9again.c. Transistorisburnedout,sograbanewone.

AlienDetectiveTable

Area/ObjectTested LEDLightUp? CommentsRanapenthroughmyhair

Yes! Aliensmightbeonthepenorinmyhair.Furthertestingneededonthedifferentareasofmyhead.

Nearatree/bush/livingplant

Neartheground(wherespecificallydidyoutest?)

Chargedballoononmyhair

Chargedfoamplatewithwool


Reading

ThissimpleFETcircuitisreallyanelectronicversionoftheelectroscopewebuiltinapreviouslesson.This“AlienDetector”isasuper‐sensitivestaticchargedetectormadefromafewpartsfromRadioShack.Ioriginallymadeafewoftheseandplacedtheminsoapboxesandnailedthelidsshutandaskedkidshowtheyworked.(IdidpokeaswitchandtheLEDsotheywouldhavesomehelpastheyfigureditout.)

Afteryou’vemadeyourchargedetector,turnitonandcombyourhair,holdingthechargedetectornearyourheadandthenthecomb.You’llnoticethatthecombmakestheLEDturnoff,andyourhead(incertainspots)makestheLEDgoon.Soit’sapositivechargestaticdetector…thisisimportant,becausenowyouknowwhentheLEDisoff,thespaceyou’redetectingisnegativelycharged,andwhenit’slitup,you’reinapocketofpositively‐chargedparticles.Howfarfromthecombdoesyourdetectorneedtobetodetectthecharge?Doesitmatterhowhumiditis?Youbet!

Youcantakeyourdetectoroutdoors,awayfromanystandingobjectsliketrees,buildings,andpeople,andholdithighintheair.WhatdoestheLEDlooklike?Whathappenswhenyoulowerthedetectorclosertotheground?Raiseitbackupagaintogetasecondreading…didyoufindthattheearthisnegative,andtheskyismorepositive?

Youcanincreasetheantennasensitivitybydanglinganextrawire(likeanalligatorcliplead)fromtheendoftheantenna.Becausethunderstormsaremovingelectricalchargesaround(negativechargesdownwardsandpositivechargesupwards),theearthiselectrifiednegativelyeverywhere.Duringathunderstorm,thefrictioncausedbythemovingwatermoleculesiswhatcauseslightningtostrike!(Butdon’ttestyourideasoutsideinthewideopenwhilelightningisstriking!)

Exercises

1. WhentheLEDison,whatdoyouthinkitmeans?

2. DoestheLEDturningoffdetectanything?

3. Doalienslikehumidity?

4. Howdoesthisaliendetectorreallywork?


Lesson#9:CosmicRayDetectorOverview:Yougettobuildaspecialcloudchamberthatwillmakeinvisibleparticlesvisible.Thiscloudchamberworksbecauseit’sfilledwithasuper‐saturatedalcohol‐watervapormix.Thealphaparticles(ions)turnthevaporintomicroscopicclouds.

WhattoLearn:Acosmicrayisnotlikearayofsunshine,butratherisasuper‐fastparticleslingingthroughspace.Thinkofthrowingagrainofsandat100mph‐that’swhata”cosmicray”is.Sincethesearetiny,chargedparticlesandnotgrainsofsand,webuilttheelectroscopebackinLesson#5todetectelectrons.TheCosmicRayDetectorisamuchbetterdeviceforfindingcosmicraysbecauseit’sgoingtocatchnegatively‐chargedparticles(electrons,alsocalled‘betaparticles’)andpositively‐chargedparticles(called‘alphaparticles’).You’llactuallygettoseethethin,threadlikevaportrailsappearanddisappear,markingthepathleftbytheparticles.ThistypeofdetectorwascreatedbyCharlesWilsonin1894,andWilsonlaterreceivedaNobelPrize(alongwithArthurCompton)fortheirworkoncloudchambers.

Materials

SafetyAlert!You’llbeworkingwithhotglueguns,toxicchemicals,glasswarethatcanshatter,andfinger‐burning‐colddryice.Thisisnotimetomessaroundinthelab.Stayalertandworkcarefullytogetyourexperimenttowork.

rubbingalcohol cleanglassjar blackfelt hotgluegun magnet flashlight scissors dryice goggles heavyglovesforhandlingthedryice(adultsonly)

ImportantProjectConsiderations:Aftercreatingyourdetector:Youcanbringyouralphaparticledetectornearasmokealarm,anoldglow‐in‐the‐darkwatchdialoraColemanlanternmantel.Youcangoonahuntaroundyourhousetofindwheretheparticlesaremostconcentrated.Ifyouhavetroubleseeingthetrails,tryusingaflashlightandshineitonthejaratanangle.

Youwillalsobeworkingwithdryice.Thedryiceworkswiththealcoholtogetthevaporinsidethejaratjusttherighttemperaturesoitwillcondensewhenhitwiththeparticles.NotethatyoushouldNEVERTOUCHDRYICEWITHYOURBAREHANDS.Alwaysuseglovesandtongsandhandleverycarefully.Keepoutofreachofchildren‐therealdangeriswhenkidsthinktheiceisplainoldwatericeandpopitintheirmouth.

Ifyourdryicecomesinlargeblocks,theeasiestwaytobreakitintosmallerpiecesistoinsertyourhandsintoheavyleathergloves,wrapthedryiceblockinafewlayersoftowels,andhititwithahammer.Makesureyouwrapthetowelswellenoughsothatwhenthedryiceshatters,itdoesn’tspewpiecesallover.Use


ametalpieplatetoholdthechunkswhileyou’reworkingwiththem.Storeunuseddryiceinapaperbaginacoolerorthecoldestpartofthefreezer.Dryicefreezesat‐109degreesFahrenheit.Mostfreezersdon’tgetthatcold,soexpectyourdryicetodisappearsoon.

LabTime

1. Cutyourfelttothesizeofthebottomofyourjar.Gluethefelttothebottomofthejar.2. Cutoutanotherfeltcirclethesizeofthelidandglueittotheinsidesurfaceofthelid.3. Cutathirdfeltpiece,about2incheswide,andlinetheinsidecircumferenceofthejar,connectingitwith

thebottomfelt.Glueitintoplace.4. Strapgogglesonyourface.Noexceptions.5. Verycarefullypouratablespoonortwoofthehighestconcentrationofrubbingalcoholontothefeltinthe

jar.Youdon’tneedmuch.Swirlitaroundtodistributeitevenly.Dothesameforthelid.Allthefeltpiecesshouldbethoroughlysaturated.Capthejarandleaveitfortenminutes.

6. Unscrewthecap,andaskanadulttoplaceasmallpieceofdryicerightonthelid.Invertthejarrightoverthelid.Leavethejarupsidedown.Donothandledryiceyourself.

7. DONOTSCREWONTHECAPTIGHTLY!Leaveitloosetoallowthepressuretoescape.8. Sitandwaitandwatchcarefullyforthetiny,thin,threadlikevaportrails.9. Whatdoyouthinkthemagnetisfor?(Hint:keepitoutsidethejar.)

Drawapictureofyourexperimentanddescribehowitworksandlabeleachpart.


Reading

Cosmicrayshaveapositivecharge,astheparticlesareusuallyprotons,thoughoneinevery100isanelectron(whichhasanegativecharge)oramuon(alsoanegativecharge,but200timesheavierthananelectron).Onagoodday,yourcosmicrayindicatorwillblipevery4‐5seconds.Thesegalacticcosmicraysareoneofthemostimportantproblemsforinterplanetarytravelbycrewedspacecraft.

Mostcosmicrayszoomtousfromextra‐solarsources(outsideoursolarsystembutinsideourgalaxy)suchashigh‐energypulsars,grazingblackholes,andexplodingstars(supernovae).We’restillfiguringoutwhethersomecosmicraysstartedfromoutsideourowngalaxy.Iftheyarefromoutsideourgalaxy,itmeansthatwe’regettingstufffromquasarsandradiogalaxies,too!

Cosmicraysarefast‐moving,high‐energy,chargedparticles.Theparticlescanbeelectrons,protons,thenucleusofaheliumatom,orsomethingelse.Inourcase,thecosmicrayswe’redetectingare”alphaparticles.”Alphaparticlesareactuallyhigh‐speedheliumnuclei(heliumnucleiaretwoprotonsandtwoneutronsstucktogether).Theywerenamedalphaparticleslongbeforeweknewwhattheyweremadeof,andthenamejustkindofstuck.

Didyouknowthatyourhouseholdsmokealarmemitsalphaparticles?Mostsmokedetectorscontainasmallbit(around1/5,000thofagram)ofAmericium‐241,whichemitsanalphaparticleontoadetector.Aslongasthedetectorseesthealphaparticle,thesmokealarmstaysquiet.However,sincealphaparticlesareeasytoblock,whensmokegetsinthewayandblocksthealphaparticlesfromreachingthedetector,youhearthesmokealarmscream.

Alphaparticlesareprettyheavyandslow,andmostgetstoppedbyjustaboutanything,likeasheetofpaperoryourskin.Becauseofthis,alphaparticlesarenotsomethingpeoplegetveryexcitedabout,unlessyouactuallyeatthesmokedetectorandingestthematerial(whichisnotrecommended).

TheelectroscopewemadeinLesson#5candetectalphaandbetaparticles.Bothbrickbuildingsaswellaspeopleemitbetaparticles.Betaparticlesareactuallyhigh‐speedelectronsorpositrons(apositronistheantimattercounterparttotheelectron),andtheyarequick,fast,andlight.Whenanelectronhitthefoilball,ittraveleddownandchargedthefoilleaves,whichdeflectedatinybitinsidetheelectroscope.Abetaparticlehasalittlemoreenergythananalphaparticle,butyoucanstillstopitinitstracksbyholdingupathinsheetofplastic(likeacuttingboard)ortinfoil.

Exercises

1. Howdoesthisdetectorwork?

2. Doallparticlesleavethesametrail?

3. Whathappenswhenthemagnetisbroughtclosetothejar?


StaticElectricityEvaluation

StudentWorksheet

Overview:Todayyou’regoingtotaketwodifferenttests:thequizandthelabpractical.You’regoingtotakethewrittenquizfirst,andthelabpracticalattheendofthislab.Thelabpracticalisn’tapapertest–it’swhereyougettoshowyourteacherthatyouknowhowtodosomething.

LabTest&Homework

1. Yourteacherwillcallyouupsoyoucansharehowmuchyouunderstandaboutelectricalchargesandhowtheyinteractwitheachother.Sincescienceissomuchmorethanjustreadingabookorcirclingtherightanswer,thisisanimportantpartofthetesttofindoutwhatyoureallyunderstand.

2. Whileyouarewaitingforyourturntoshowyourteacherhowmuchofthisstuffyoualreadyknow,yougettochoosewhichhomeworkassignmentyouwanttocomplete.Theassignmentisduetomorrow,andhalfthecreditisforcreativityandtheotherhalfisforcontent,soreallyletyourimaginationflyasyouworkthroughit.Chooseone:a. Writeashortstoryorskitaboutstaticelectricityfromtheperspectiveoftheelectronorproton.You’ll

readthisaloudtoyourclass.b. Makeaposterthatteachesthemainconceptstostaticelectricity.Whenyou’refinished,you’lluseitto

teachtoaclassintheyoungergradesanddemonstrateeachoftheprinciplesthatyou’velearned.c. Writeandperformapoemorsongaboutstaticelectricity.Thiswillbeperformedtoyourclass.


StaticElectricityQuiz

Name__________________________________________________________

1. Whatchargedotheproton,neutron,andelectronhave?

2. Whathappenswhenyoubringtwolikechargestogether?

3. Whatchargearemostthings?

4. HowdoIknowifanobjectispositivelyornegativelycharged?

5. Whydoeshairsticktoaballoonwhenyourubitonyourhead?


6. Canyouseeelectrons?Whyorwhynot?

7. Ifyoubringachargedballoonnearastreamoforangejuice,whathappensandwhy?

8. Ihaveafoamplate,plasticbag,abottleofrubbingalcohol,andapieceofwool.HowcanIgenerateapositiveelectricalcharge?HowwillIreallyknowit’spositive?

9. Whatdoesanelectroscopedetect?Howdoyouknowwhenithasdetectedit?

10. Whydoesaneonbulblightupwhenbroughtclosetoastaticsource?


11. Whydotheleavesintheelectroscopetakeonthesamechargeasthefoilball?

12. DrawadiagramthatshowstheyardstickElectrostaticMotorexperimentset,andthelocationofthepositiveandnegativechargesontheballoonandtheyardstick.Yourdiagramshouldclearlyexplainwhat’sgoingonandwhy.Youcanuseanothersheetofpaperifneeded.


StaticElectricityLabPracticalStudentWorksheet

Thisisyourchancetoshowhowmuchyouhavepickeduponimportantkeyconcepts,andifthereareanyholes.Youalsowillbeworkingonahomeworkassignmentasyoudothistestindividuallywithateacher.

Materials:

balloon pingpongball paper

LabPractical:

Designandbuildanexperimentthatshowshowelectrically‐chargedobjectsattracteachother.

Designandbuildanexperimentthatshowshowelectrically‐chargedobjectsrepeleachother.

Explainhowobjectsthatareelectricallychargedcancreateatemporarychargeonanotherobject.


Section2:Electricity

Whystudyelectricity?Whileit’struethatyoudon’tneedtoknowhowelectricityworksinordertofliponalightswitch,youdoneedtoknowathingortwoaboutcircuitsbeforeyoustartwiringupyourownrobot.

Electricityisallaroundyou,fromthetinysubatomicleveloftheelectrontothegiganticsolarstormsfromthesun.

Whenyou’redonewiththislesson,you’llknowhowtowireupcircuitsforunderwatervehicles,createyourownroboticssensors,extractenergyfromfruit,splitawatermolecule,andreallymakesparksfly.Areyouready?Thisvideowillgetyoustartedontherightfootforyourstudyintoelectricity.

Althoughwecan't”see”electricityflowthroughwires,youcancertainlysee,hear,andfeelitseffects:thelightbulbflashingon,thehairdryerblowing,theheatgeneratedbyahotwire,andsoforth.Inordertounderstandelectricity,though,we’regoingtotalkaboutwaterbecausethat’ssomethingthatyoualreadyhaveexperiencewith.

Electricityislikewatergoingthroughapipe.Imagineyouhaveabigpipeconnectedinacircle,soitconnectsbacktoitselfinaloop.Thewaterneedsapumpinordertomovethroughthepipe.Electricityislikethewatergoingthroughthepipe,andthebatteryislikethepump.

Nowimaginebreakingopenyourpipetoinsertawaterwheel.Sealupthecracksandturnonyourpump.Canyouimaginewhathappensnow?Whenthepump(battery)turnson,thewater(electricity)flowsthroughthepipeandturnsthewaterwheel.Thewaterwheelislikeyourmotororlightbulb.

Supposeyouaddinavalvesoyoucanturnthewateronandoffthroughyourpipe.Whatisthevalvelikeinyourcircuit?It’sjustlikeaswitchinacircuit,becauseitinterruptstheflowofelectricity.

Whatwouldhappenifyoubrokeyourpipe?Imagineyouhaveasledgehammerandyousmashedopenthepipe.Doesitmatterwhichsideofthewaterwheelyoubreakiton?Itdoes!Ifyoubreakitbeforethewaterwheel,thewaterwheelwon’tturn.Ifyoubreakitafterthewaterwheel,itmightturnforaminute,butthenitwillstopbecausethere’snomorewatergoingintothepumpbecauseyoubustedopenthepipe,sotheflowstopseitherway.That’swhathappenswhenyoudisconnectoneofyourwiresinyourcircuit.Nomoreelectricitycanflow.

Nowimagineyou’vegotawhole,completepipeagain.Whatwouldhappenifwetakeoutthepump,turnitaround,andstickitbackinagain?Thewatergoestheotherway!Whatdirectiondoesthewaterwheelgo?Itstartsturningintheoppositedirectionalso.

Somewaterwheelsaredesignedtogoeitherforwardorbackward,whileotherwaterwheelscanonlymoveforwardduetotheshapeoftheirbladesandhowtheyweremade.SomeelectricalcomponentslikebuzzersandLEDsarepolarized,meaningthattheydonotworkbackward.Otherelectricalcomponents,likemotorsandlightbulbs,doworkforwardsandbackward.Whenyouworkwithcircuits,ifyoufindacomponentthatdoesn’twork,tryturningitaroundinthecircuittoseeifthatfixesit.

Therearemanydifferentelectricalcomponentsthatmaketheelectronsreactindifferentways,suchasresistors(whichlimitcurrent),capacitors(thesecollectacharge),transistors(thesearelikeanelectronicgateforelectricity),relays(electricityitselfactivatesaswitch),diodes(whichareaone‐waystreetforelectrons),solenoids(areanelectricalmagnet),switches(whicharestoplightsforelectrons),andmore.We’regoingtouseacombinationofLEDs,buzzers,andmotorsinourcircuitsinourunittogether.


ACIRCUITlookslikeaCIRCLE.WhenyouconnectthebatteriestotheLEDwithwireandmakeacircle,theLEDlightsup.Ifyoubreakopenthecircle,electricity(current)doesn’tflowandtheLEDturnsdark.LEDstandsfor“LightEmittingDiode”.Diodesareone‐waystreetsforelectricity–theyallowelectronstoflowonewaybutnottheother.

Rememberwhenyouscuffedalongthecarpet?Yougatheredupanelectricchargeinyourbody.Thatchargewasstaticuntilyouzappedsomeoneelse.Themovementofelectricchargeiscalledelectriccurrent,andismeasuredinamperes(“A”).

Whenelectriccurrentpassesthroughamaterial,itdoesitbyelectricalconduction.Therearedifferentkindsofconduction,suchasmetallicconduction,whereelectronsflowthroughaconductor(likemetal)andelectrolysis,wherechargedatoms(calledions)flowthroughliquids.


Lesson#10:BasicCircuitsOverview:Thislabwillgetyoufamiliarwithhowtohookupasimplecircuitsowecanmovetomorecomplexstuffsoon,likemotors,switches,andremotecontrols.Butfirst…thebasics.

WhattoLearn:Rememberwhenyouscuffedalongthecarpet?Yougatheredupanelectricchargeinyourbody.Thatchargewasstaticuntilyouzappedsomeoneelse.Themovementofelectricchargeiscalledelectriccurrent,andismeasuredinamperes(A).Whenelectriccurrentpassesthroughamaterial,itdoesitbyelectricalconduction.Therearedifferentkindsofconduction,oneofwhichiscalledmetallicconduction,whereelectronsflowthroughaconductor,likemetal.

Materials

2AAbatteries AAbatterycase 2alligatorwires LEDs

SafetyTip:Irecommendusingthesuper‐cheapkindofbatteries(usuallylabeled“HeavyDuty”or“SuperHeavyDuty”),usuallyfoundatdollarstores.Thesetypesofbatteriesarecarbon‐zinc,whichdonotcontainacidthatcanleakandexposeyoutotoxicchemicals.Whenyoushortthecircuitsandoverheatsthebatteries(whichyoushouldexpect,bytheway),it’snotdangerous.Alkalinebatteries(likeEnergizerandDuracell)willgetsuper‐hotandleakacid,sothosearen’ttheonesyouwanttoplaywith.

LabTime

1. Followingthevideoinstructions,usethematerialstowireupasimplecircuitandgettheLEDtolightup:a. Insertyourbatteriesintothecase.Flatside(minus)goestothespring.b. Attachonealligatorcliptoeachofthemetaltipsofthewiresfromthebatterycase.Makesure

you’vegotagoodmetal‐to‐metalconnection.Youshouldnowhavetwoalligatorclipsattachedtothebatterypack.

c. Attachtheendofthealligatorclipsthat’sconnectedtotheblackwire(negative)fromthebatterycasetotheflatsideoftheLED.Itdoesn’tmatterwhatcolorthealligatorclipwireis.

d. Attachtheotheralligatorclipthat’sconnectedtotheredwire(positive)fromthebatterycasetothelongerLEDwire.Again,itdoesn’tmatterwhatcolorthealligatorclipwireis.

e. YourLEDshouldlightup!2. OnceyourLEDisilluminated,whathappensifyoutakeitoutandinsertitintheoppositewayintothe

circuit?(Reversethepolarity.)Doesitstillwork?3. Troubleshootingacircuitthatdoesn’twork:

a. Batteriesinsertedintothecasethewrongway?(Flatsideofthebatteryshouldgotothemetalspringinsidethecase.)

b. LEDisinthecircuitthewrongway?Remember,LEDsarepickyaboutplusandminus,meaningthatitmatterswhichwaytheyareinthecircuit.IfyouchooseabipolarLED,thenyoudon’thaveto


worryaboutthisone,sincetherearetwoLEDs,oneineachdirection,inoneLEDpackagewhichwillilluminatenomatterwhichwayyouhaveitinyourcircuit.LEDsarepolarized.

c. Isthereametal‐to‐metalconnection?You’renotgrabbingtheplasticinsulation,areyou?Notevenatinybit?Sometimeskidshavetheedgeofthealligatorclipleadproppedupontheedgeoftheplasticinsulation,whichwillmakeyourconnectionnotwork.

d. Onceinawhile,you’llgetabadalligatorwire.There’saneasytocheckthis:removeyouralligatorclipleadsfromthecircuitandtoucheachofthemetaltipsfromthebatterypackwirestotheLEDwires.IftheLEDlightsup,swapoutyouralligatorclipleadwiresfornewonesandthatshouldfixit.

Reading

Whenelectriccurrentpassesthroughamaterial,itdoessobyelectricalconduction.Therearedifferentkindsofconduction,suchasmetallicconduction,whereelectronsflowthroughaconductor,likemetal,andalsobyelectrolysis,wherechargedatomscalledionsflowthroughliquids(we’llbegettingtothatlater).

Althoughwecan'tseeelectricityflowthroughwires,youcancertainlysee,hear,andfeelitseffects:thelightbulbflashingon,thehairdryerblowing,theheatgeneratedbyahotwire,andsoforth.Inordertounderstandelectricity,though,we’regoingtotalkaboutwater,becausethat’ssomethingthatyoualreadyhaveexperiencewith.

Electricityislikewatergoingthroughapipe.Imagineyouhaveabigpipeconnectedinacircle,soitconnectsbacktoitselfinaloop.Thewaterneedsapumpinordertomovethroughthepipe.Electricityislikethewatergoingthroughthepipe,andthebatteryislikethepump.

Nowimaginebreakingopenyourpipetoinsertawaterwheel.Sealupthecracksandturnonyourpump.Canyouimaginewhathappensnow?Whenthepump(battery)turnson,thewater(electricity)flowsthroughthepipeandturnsthewaterwheel.Thewaterwheelislikeyourmotororlightbulb.

Supposeyouaddinavalvesoyoucanturnthewateronandoffthroughyourpipe.Whatisthevalvelikeinyourcircuit?It’sjustlikeaswitchinacircuit,becauseitinterruptstheflowofelectricity.

Whatwouldhappenifyoubrokeyourpipe?Imagineyouhaveasledgehammerandyousmashedopenthepipe.Doesitmatterwhichsideofthewaterwheelyoubreakiton?Itdoes!Ifyoubreakitbeforethewaterwheel,thewaterwheelwon’tturn.Ifyoubreakitafterthewaterwheel,itmightturnforaminute,butthenitwillstopbecausethere’snomorewatergoingintothepumpbecauseyoubustedopenthepipe,sotheflowstopseitherway.,That’swhathappenswhenyoudisconnectoneofyourwiresinyourcircuit.Nomoreelectricitycanflow.

Nowimagineyou’vegotawhole,completepipeagain.Whatwouldhappenifwetakeoutthepump,turnitaround,andstickitbackinagain?Thewatergoestheotherway!Whatdirectiondoesthewaterwheelgo?Itstartsturningintheoppositedirectionalso.

Somewaterwheelsaredesignedtogoeitherforwardorbackward,whileotherwaterwheelscanonlymoveforwardduetotheshapeoftheirbladesandhowtheyweremade.SomeelectricalcomponentslikebuzzersandLEDsarepolarized,meaningthattheydonotworkbackward.Otherelectricalcomponents,likemotorsandlightbulbs,doworkforwardandbackward.Whenyouworkwithcircuits,ifyoufindacomponentthatdoesn’twork,tryturningitaroundinthecircuittoseeifthatfixesit.


Ifyoulookaroundtheroom,doyounoticethedifferentkindsoflightbulbsyouhave?Youmightfindafluorescentbulb,anincandescentlightbulb,aneonbulbanLED,orevenahalogenlamp.What’sthedifferenceinhowtheseproducelight?

Theincandescentlightbulbusesawirethatglowswhenelectriccurrentrunsthroughit.Tokeepthewirefromburningitselfup,theairisremovedfromthebulbandreplacedwithaninertgas.Thewireismadefromtheelementtungsten.

Neonbulbslightupbecausetheelectricalfieldexcitesthegas,whichthengivesoffapinkish‐orangelight.

Afluorescenttubeislinedwithwhitestuffcalledphosphor,whichgivesofflightwheneverit’sstruckbyUVrays.ThetubeisfilledwithagasthatgivesoffUVrayswhenplacedinanelectricalfield.Whenthebulbisbroughtclosetoastaticcharge,electronsripthroughthetubeandgoouttheotherside.Astheygothrough,theysmackintothegasvaporwhichreleaseslightrays(UVinafluorescenttube)thathitthephosphorontheinsideofthetube,whichthenemitslight.Fluorescentlights,oranytubeofgasfromthenoblegasescolumnontheperiodictable,likeneon,willalsoglowinanelectrically‐chargedfield.

LEDstandsfor“LightEmittingDiode."Theydon'thaveafilamentsotheydon'tgethot.Theylightupbythemovementofelectronsinasemiconductormaterial(moreonthislater),andtheylastalongtime,likethousandsofhours.

Forhalogenlamps,insteadofcreatingavacuumlikewithincandescentbulbs,theyfillthebulbwithahalogengassothatthefilamentwillburnbrighter.It’snotthegasthat’silluminating,butratherthefilamentitself.

Exercises

1. WhatdoesLEDstandfor?

2. DoesitmatterwhichwayyouwireanLEDinacircuit?

3. DoesthelongerwireontheLEDconnecttoplus(red)orminus(black)?

4. Doyouneedtohookupbatteriestomakeaneonbulblightup?Whyorwhynot?

5. What'sthedifferencebetweenalightbulbandyourLED?

6. Whatisthedifferencebetweenaboltoflightningandtheelectricityinyourcircuit?

7. Whatisthechargeofanelectron?


Lesson#11:ConductivityTestersOverview:Todayyougettowireupasimplecircuitandtestavarietyofobjectstofigureoutiftheyareinsulatorsorconductorsofelectricity.

WhattoLearn:Takespecialnoteastowhichkindsofmaterialsareinsulatorsandwhichareconductorsofelectricity.Metalsareconductorsnotbecauseelectricitypassesthroughthem,butbecausetheycontainelectronsthatcanmove.

Materials

2AAbatteries AAbatterycase 3alligatorwires LEDs

LabTime

1. It’stimetowireupyourdetector.Here’swhatyouneedtodo:a. RemoveoneofthealligatorclipsfromtheLED(itdoesn’tmatterwhichone)andletitdangle.b. AddathirdalligatorcliptotheLED–rightinthesamespotastheoneyoujustremoved.Theother

endshouldbedanglingalso.c. Holdthecircuitbythetwodanglingalligatorclips,andtouchtheirtipstogether.TheLEDshould

lightup.d. BreakcontactandtheLEDgoesdark.TouchthemtogetheragainandtheLEDlightsup.On.Off.On.

Off.On.Thisistheworld’ssimplestswitch.e. Nowtoucheachofthetwoalligatorclipstoeithersideofanobjectyouthinkwillconduct

electricity.Whatdidyoutestandwhathappened?

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______________________________________________________________________________________________________________________________________________________________________________________________________________________________

2. Filloutthedatatable:


Conductivity&InsulatorTestersDataTable

Object IsitaConductor?

IsitanInsulator?

Notes:


Reading

Metalsareconductorsnotbecauseelectricitypassesthroughthem,butbecausetheycontainelectronsthatcanmove.Aninsulatordoesnotallowelectronstomove.

Thinkofthemetalwirelikeahosefullofwater.Thewatercanmovethroughthehose.Aninsulatorwouldbelikeahosefullofcement‐nochargecanmovethroughit.

Allmetalsconductelectricity:however,somemetalslikecopperandgoldconductbetterthanothersbecausetheyhavelessinternalresistance(whichrelatestohowthemetalisstructured.)Metalshavefreeelectronswhichcanmovefromatomtoatom,allowingtheelectricitytoconductthroughthem.Paper,rubber,andplasticsmakegreatinsulators,becausesometimesyoudon’twantelectricitytoflowunlessyousayso.We’regoingtotalkaboutswitcheswhenwemakeourburglaralarmslateron.

Exercises

1. Namesixmaterialsthatareelectricallyconductive.

2. Whatkindsofmaterialsareconductorsandinsulators?

3. Canyouconvertaninsulatorintoaconductor?How?

4. Namefourinstanceswheninsulatorsareabadideatohavearound.

5. Whenareinsulatorsessentialtohave?


Lesson#12:Switches&Motors

Overview:Whenyouturnonaswitch,it’sdifficulttoreallyseewhat’sgoingon.Soyou’regoingtomakeyourownfrompaperclips,brassfasteners,andindexcards.Andyougettoplaywithrealmotors,too.

WhattoLearn:Thinkofthisswitchlikeatraintrack.Whenyouthrowtheswitchesoneway,thetrain(electrons)canracearoundthetrackattopspeed.WhenyouturntheswitchtotheOFFposition,it’slikeabridgecollapseforthetrain–there’snowayfortheelectronstojumpacrossfromthebrassfastenertothepaperclip.WhenyouswitchittotheONposition(bothsides),you’verebuiltthebridgesforthetrain(electrons).

Materials

2AAbatteries AAbatterycase 2alligatorwires 1.5‐3VDChobbymotor 1indexcard 2brassfasteners 1largepaperclip propellerorpieceoftapeforthemotorshaft

YoudecideifyouwanttocompletePart3.Ifthat’sthecase,you’llalsofindtheseitemssetoutforyou:

6brassfasteners 1indexcard 2largepaperclips 6alligatorclipleadwires

LabTime

1. Today,we’regoingtolearnhowtoturnamotoronandoffbycontrollingwhentheelectricitygoesthroughthecircuitbyusingaswitch.Themotorswe’reusingareoneofthosespecialelectricalcomponentswhicharenotpolarized,meaningifyoustickitinbackward;itwillstillrun…butbackward.

2. SPSTstandsforSinglePoleSingleThrow,whichmeansthattheswitchturnsononlyonecircuitatatime.Whentheswitchisengaged,currentflows.Whenit’snot,thecircuitisbrokenopenandelectricitystops.SPSTstandsforSinglePole,SingleThrow,whichmeansthattheswitchturnsononlyonecircuitatatime.Thisisagreatswitchforturningonemotoronandoff.

3. DPDTstandsforDoublePoleDoubleThrow,andyouneedthiskindofswitchtohandlethecircuitryrequiredtomakeamotorgoinreverse.That’sinPart3ofthisexperiment.

4. Therearethreedifferentpartstothisexperiment–you’llbedoingParts1&2forsure,butPart3istotallyoptional.


LabTime

Part1:Makingamotorturn.

1. Grabholdofyourmaterialsandmakethemotorturnon.Doyouseethosetwolittleterminalsonthebackofthemotor?That’swhereyouhookupthealligatorwires.It’sjustlikelightingupanLED,onlyinsteadofwires,therearetabs.

2. Sincethesemotorsspinquicklyandtheshaftistiny,addapieceoftape(unlessyou’reusingpropellers)totheshafttoseethespinningactionmoreclearly.

3. Canyoumakeyourmotorgoinreverse?(Hint:rememberthewaterwheel?)

4. CanyouhookupboththeLEDandmotoratthesametime?

Part2:Switchingthemotoronandoffusingaswitch.Followyourinstructorthroughthesesteps:

1. MakingtheSPSTswitch:a. OpenthepaperclipintoaV‐shape.b. Stickthebrassfastenerthroughthepaperclipandthroughtheindexcard,makingsurethesmaller

loopofthepaperclipisonthebottom.c. Openthebrassfastenerupontheotherside.d. Measurewherethesecondbrassfastenerneedstogoinordertomissthelowerloopbuthitthe

largerloopwhenthepaperclipispressed.Insertthebrassfasteneratthemarkandopenitupontheotherside.Thepaperclipshouldnotbetouchingthesecondbrassfasteneryet.

e. Makesurethebrassfastenersaren’ttouchingontheundersideofthecard,oryou’llbypasstheswitch.

f. Pressdownontheupperlooptobesureittouchesthebrassfastener,andspringsbackupwhenyouletgo.You’vejustmadeaNO(normallyopen)switch,meaningthattheswitchisopen(nocurrentflows)untilit’sactivated.Nowlet’shookitupinacircuit.

2. Nowremoveonewirefromthemotorterminalandreplaceitwithathirdalligatorwirelikewedidwiththeconductivitytesterexperiment,onlythistimeit’samotorandnotanLED.Whenyoutouchthetwofreeends,makesurethemotorstillruns.

3. Insteadofhavingthealligatorclipleadstouchingeachother,connecteachonetoabrassfastenerontheundersideoftheindexcard.

4. Presstheswitch–themotorshouldturn.Ta‐daa!5. Tracethepaththeelectricitytakeswiththeirfinger.Whatdidyoufindout?Writeithere:

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Part3:Makingthemotorgoforwardandreverseusingasingleswitch.Followyourinstructor’sdirections:

1. MakingtheDPDTswitch:a. We’regoingtoputsixbrassfastenersonthecard,threeineachrow.Insertthetwomiddlebrass

fastenersfirst,eachwiththeirownpaperclipattached.Openthemupontheothersideandtapethemdownontheundersidesotheyareoutofreachofotherfastenersbutcanstillbeattachedtoalligatorclipleads.

b. Moveboththepaperclipsupandmarkthenextlocationforthefasteners.Inserttwofasteners,oneoneachside,andopenthemupontheundersideofthecard.Tapeintoplace.

c. Movethepaperclipsdownandmarkthelastsetofpointsforthelasttwofasteners.Insertfasteners,openup,andtape.

d. Showthekidshowtooperatetheswitchandhavethempracticebeforewiringitup.Bothpaperclipsupmeansforward,bothdownisreverse.Nocontactisoff.

e. Workingontheundersideofthecard:usetwoalligatorclipstomakethe“X."Connectonealligatorcliptoacorner(itdoesn’tmatterwhich)andtheotherendconnectstothefastenerintheoppositediagonalcorner.Ifyougrabthestemsthatarepeekingoutofthetape,it’seasiertoconnectto.Dothisforbothdiagonals.

f. Connectonealligatorclipwiretothenegativewireonthebatterybackandthentooneofthemiddlebrassfasteners.

g. Connectonealligatorclipwiretothepositivewireonthebatterybackandthentotheothermiddlebrassfastener.

h. Connectonealligatorwiretoeachmotorterminal(youshouldhavetwowiresconnectedtoyourmotor).Connecttheotherendsofthewirestotwobrassfastenersononeendoftheswitch(itdoesn’tmatterwhich),buttheymustbeonthesameend.

i. Testyourmotorandseehowitworks!Ifitdoesn’twork,removeallthewiresandredostepsf‐h.Ifyoustillhavetrouble,grabanewsetofwiresandseeifthishelps.

2. Tracethepaththeelectricitytakeswithyourfinger.Whatdidyoufindout?Writeithere:

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Reading

DoyourememberhowtheyardstickmovedaroundinacircleusingaballoonwaybackinLesson#6:TheElectrostaticMotor?Usingstaticchargeattraction,theyardstickfollowedtheballoonaroundinacircle.

Imaginemodifyingtheexperimentsothattherewasachargedballoonphysicallyattachedtotheendoftheyardstick,sothatyoucoulduseapositivelychargedobjecttoattractandpulltheyardsticktowardyou,andthenjustasthestickwasclose,youquicklyswitchedtoanegativelychargedobjecttopushtheobjectaway.That’showtheelectrostaticbottlemotorworkedinapreviousexperiment.

Nowplacethosestaticallychargedobjectswithmagnets.You’vegotamagnetonsomethingwhichcanmoveinacircle,andanothermagnetyoucanflipNorth‐Southdependingonwheretherotatingmagnetis.That’showamotorworks!We’regoingtoactuallybuildamotorusingtheseprincipleswhenwegettoelectromagnetism,andwehavetowaitabitbeforemakingonebecausewe’regoingtomakeamagnetthatwecanturnonandoffforthatproject,andthere’safewmorethingsweneedtolearnhowtodofirst.

Rememberthewateranalogy?Supposeyouaddinavalvesoyoucanturnthewateronandoffthroughyourpipe.Whatisthevalvelikeinyourcircuit?It’sjustlikeaswitchinacircuit,becauseitinterruptstheflowofelectricity.Therearedifferentkindsofswitches,buttheyalldothesamething:allowyoutocontrolwhenelectricityflowsthroughthecircuit.

Thinkofthisswitchlikeatraintrack.Whenyouthrowtheswitchesoneway,thetrain(electrons)canracearoundthetrackattopspeed.WhenyouturntheswitchtotheOFFposition,it’slikeabridgecollapseforthetrain–there’snowayfortheelectronstojumpacrossfromthebrassfastenertothepaperclip.WhenyouswitchittotheONposition(bothsides),you’verebuiltthebridgesforthetrain(electrons).


Exercises

1. Ifyouwanttoreversethespindirectionofamotorwithoutusingaswitch,whatcanyoudo?

2. Asimpleswitchcanbemadeoutofwhatkindsofmaterials?

3. HowwouldyoumakeyourSPSTswitchanNC(normallyclosed)switch?

4. HowdidyouhavetoconnectyourcircuitinorderforboththeLEDandmotortoworkatthesametime?Drawithere:

5. DrawapictureofyourexperimentthatexplainshowtheSPSTswitchworks,andshowhowelectricityflowsthroughyourcircuit:

ExtraCredit(forstudentswhohavecompletedPart3):

6. DrawapictureofyourexperimentthatexplainshowtheDPDTswitchworksinyourcircuitandshowhowtowireupthecircuit.


Lesson#13:DigitalMultimetersOverview:Todayyou’regoingtolearnhowtouseoneofthemostimportanttoolsthatscientistsuse.You’llgetto“see”electricityasyoutestthem.Andyou’llneverhavetowonderifabatteryisgoodorbadagain.

WhattoLearn:Althoughthesearethemostcommonelectricaltesters,there’smorethanonedeviceinthatbox.Itmeasuresvolts,amps(current),andresistance(howeasyitisforelectricitytogetthroughawire).We’regoingtolearnhowtouseitinauseful,practicalwaytomeasurevoltsanddetectproblemswithnon‐workingcircuits.

Materials

DigitalMultimeter(DMM) CircuitequipmentfromExperiments10‐12fortesting

LabTime

1. PlugyourprobesintotheDMM.Theblackleadgoestoground.Pushitinalltheway.2. Puttheredleadintheholethatsays“V”forvolts.Itusuallyhasthe“Ω”symbol(pronounced“omega”)

whichstandsforohms,oritmightsay“ohms,"oreven“mA”formilli‐amps.Don’tputitintheholethatsays“10A”–that’sfortestinglargecurrentslikeinyourhouse.

3. Turnthedial.Feelhowitclicks?4. Youcantesttwodifferentkindsofvoltage:DCandAC.ACisthekindinsideyourhousewiring.We’regoing

totestDCwithourcircuit.SetyourarrowonthemetertotheDCvoltage,whichistheVwithastraightlineontopofit(theVwithasquigglinglineisACvolts).SettheknobintheDCvoltareatothemarkthatsays“20."

5. TakeanAAbatteryandtouchoneprobeendtotheplus,andtheotherprobetotheminus.Youshouldgetareading.WhatdidyougetforareadingonyourDMM?(RemembertowriteVafterthenumberfor“volts”.)

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6. Testyoursecondbatteryandwritethereadinghere:

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Ifthebatteryisgood,itshouldreadbetween1.4–1.6volts,dependingonhowfreshtheyare.Brandnewbatteriesgiveahigherreading.Generally,ifAA,AAA,C,orDcellbatteriesread1.3voltsorhigher,theyaregoodandwillworkinyourcircuit.Iftheyreadbetween1–1.3volts,theymayormaynotwork,dependingonthetypeofcircuityou’reusingthemin.Anythinglessthan1voltwon’tworkandshouldbedisposedof.9Vbatteriesaregoodbetween7‐9volts.


7. Insertyourbatteriesintothebatterycase.Touchtheprobetestleadstotheendsofthewiresfromthebatterycase.Whatdoyouread?______________________________________________________________________________________________________________

8. Wireupacircuitthatusesabatterypackandamotor.9. Usingyourprobes,touchatestprobetoeachterminalofthemotorandreadhowmanyvoltsyouhaveat

themotor.Themotorisusingabunchofvolts,soit’sgoingtovary.Sohere’showyoureadhowmanyvoltsthemotorisreallygetting:disconnectthealligatorclipwiresfromthebackofthemotor(sothemotornolongerinthecircuit)andattachtheminsteadtojusttheprobes.Whatdoyouread?

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10. Discusswiththestudentsabouthowtodifferentiateobservationfrominference(interpretation).Scientists’explanationscomepartlyfromwhattheyobserveandpartlyfromhowtheyinterprettheirobservations.Aftertheytaketheirdata,askthemiftheynoticeanypatternsintheirdata.

Takingturns,haveonelabpartnerwireuponepartofacircuitincorrectly,likeputtingtwoalligatorclipwiresononeLEDlead,puttingabatteryinbackward,etc.Keepitsimple,butthecircuitshouldn’tworkatfirst.UsetheDMMtofigureoutwheretheproblemis.Nowfilloutthedatatable:


DMMDataTable

TypeofCircuitTested ComponentTested Result NotesSimplecircuitwithamotorandbatterypack.

Batterypack Zerovolts. Batterywasnotpushedinalltheway.


Reading

ADMM(DigitalMulti‐Meter)orDVOM(DigitalVoltageOhmMeter)isahandhelddevicethatscientistspulloutwhenthingsgowrong.Thishandytoolcandetectproblemswithelectronics,motorcontrols,appliances,powersupplies,andcircuitsinnotime.

It’snotenoughtoknowhowtousethebuttonsanddial.Youalsohavetoknowhowtotestyourcircuit.That’swhatwe’regoingtodowiththislab.

Ifyoulikehistory,thefirstdevicetodetectcurrentwasagalvanometer(we’remakingoneoftheselateron)waybackin1820.Itwasn’tuntilthe1920swhenvacuum‐tubeelectronicswerecommonthatthefirstmultimeterwasinventedbyanupsetengineerwhowasfrustratedthathehadtocarryaroundsomanydifferentdevicestodohisjobmaintainingtelecommunicationcircuitswiththeBritishPostOffice.

Exercises

1. Ifyoumeasure2.65voltsfromyourbatterypack,doyouneednewbatteriesorwilltheywork?

2. HowdoyouthinkyouwouldmeasuretheresistanceofanLED?

3. Resetyourmeterforaquickpracticaltest:RemovethewiresfromyourDMMandsetthedialatOFF.Waveyourhandwildlyandshowhowyoucanusethemeter(youcanaddprobesandturnitonnow)totestthevoltageonyourLEDinasimplecircuitdoingthestepsfromtheexperiment.


Lesson#14:MotorSpeedControllersOverview:YoualreadyknowhowtoturntheLEDonandoff.Youcanevenmakeamotorgoforwardandreverse.Butwhatifyouwanttochangethespeedofthemotor?OrhowbrightordimtheLEDlightsup.Todayyou’llbeabletodojustthat.

WhattoLearnOnceyouunderstandhowtousethispotentiometerinacircuit,you’llbeabletocontrolthespeedofyourlaserlightshowmotorsaswellasthemotorsandlightsonyourrobots.

Materials

2AAbatteries AAbatterycase 3alligatorwires potentiometer(1kworksbest) 1.5‐3VDChobbymotor LED Optional:DMM

LabTime

1. WireupasimplecircuitwiththeLEDandmakeitlightup.2. ReplaceoneoftheLEDalligatorclipleadswithathirdwire,aswedidinExperiment11:Conductivity

Testers.3. Takethetwofreealligatorclipsendsandconnectonetothemiddletabofthepotentiometer,andtheother

tooneoftheremainingtabs.4. Turntheknob.Whathappened?

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5. Movethesecondalligatorcliptotheotherterminal.Howdoesthischangethecircuit?____________________________________________________________________________________________________________

6. CanyouuseamotorinsteadofanLED?Tryitnow.Whathappened?____________________________________________________________________________________________________________


7. Ifyouhavetroublewiththemotor,here’sanalternativecircuityoucantrythatisaVoltageDividercircuit,usingavariablevoltagesupplyforthemotor:

a. Connectthepositivebatterywirestooneofthepotentiometer’sresistiveterminals(notthemiddleterminal)usinganalligatorcliplead.

b. Connectthenegativebatterywiretotheotherresistiveterminalonthepotentiometer(again,notthemiddlewiperterminal)usinganotheralligatorcliplead.

c. Connectathirdalligatorclipleadbetweenoneofthemotorterminalsandthewiper.d. Connectafourthalligatorclipleadtothelastmotorterminalandrightontopofthenegative

batterywire.Youwillhavetwoalligatorclipleadsattachedatthispoint.Makesuretheyallmakegoodcontact.

e. Turntheknob…doesthemotorturn?

1. Optional:Youcandothisasademopieceifyou’reshortonequipmentortime.a. Disconnectyourpotentiometerfromthecircuit.UseyourDMM,turningyourdialtothe“Ω”symbol

tomeasuretheresistanceinohms.b. Touchyourprobestothewiperandoneoftheresistiveendsandreadameasurement.What

happenstoyourreadingwhenyouturntheknob?Howhighandlowdothenumbersgo(whatistherangeofthepotentiometer)?

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c. Withapencil,drawalonglineonasheetofpaper.Touchoneoftheprobestotheendoftheline.Touchtheotherprobetoaspotanywhereelseontheline.Whatdoyouread?

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d. Whatifyoumoveyourpencilfurtherdowntheline?Doesthischangethereading?How?

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Reading

Apotentiometer(sometimesreferredtoaspot)isaresistorwiththreeterminalsthathasaslidingcontacttovarytheresistance.Resistanceisameasureofhoweasilycurrentflowsthroughawire.Themoretheresistance,thelesscurrentflowsthroughthecircuit.We’regoingtouseoursasavariableresistor.Ineverydaylife,potentiometersareeverywhere:volumecontrols,oldradiodials,andinsidejoysticksasawaytodetectposition.

Ifyouhaveanextra,pullitapartsoyoucanseetheslidingcontact(calleda‘wiper’)thatmovesalongtheresistiveelement.Thewiperisthemiddlecontactandtheresistiveelementsaretheterminalsoneitherside.

Exercises

1. Howdoesapotentiometerwork?

2. DoesthepotentiometerworkdifferentlyontheLEDandthemotor?

3. Namethreeplacesyou’veusedpotentiometersineverydaylife.

4. HowdoyouthinkyoumightwireupanLED,switch,andpotentiometer?


Lesson#15:ElectricEyeSensorOverview:Photoresistorsareveryinexpensivelightdetectors,andyou’llfindthemincameras,streetlights,clockradios,robotics,andmore.We’regoingtoplaywithoneandfindouthowtodetectlightusingasimpleseriescircuit.

WhattoLearn:Thisisthefirstofmanydifferentburglaralarmswe’regoingtomakewithoursimplecircuitsandswitchesknowledge.Payspecialattentiontohowthisgetsinsertedinyourcircuit.Noticeanysimilaritiestotheswitchcircuit?We’regoingtousetheideaofwiringupcomponentsinseriesoverthenextcoupleofBurglarAlarmlessons.

Materials

AAbatterycasewithbatteries oneCdScell threealligatorwires LED Optional:Laserpointerorflashlight(orboth) Optional:DMM(DigitalMultimeter)

LabTime

1. SeparatethewiresofyourCdScell.2. LightupyourLEDinasimplecircuit.Don’tputintheCdScellyet–wewanttobesureeverythingworks

beforeintroducinganewelectronicelement.3. RemoveoneofthealligatorclipsfromanLEDwireandreplaceitwithathirdalligatorcliplead.4. AttacheachoneofthetwofreeendsofalligatorwirestoeitherendoftheCdScell.Youshouldnowhavea

completecircuitthatlooksalotlikeacirclewhenyoustretchitout.5. PutyourhandovertheCdSlightdetectorandtheLEDshouldgodark.6. ShineaflashlightorlaserpointerontheCdScell(orjustgooutsideinthesun)andtheLEDwilllightup.If

youusedthesunforalightsource,you’llneedtocupyourhandsaroundtheLEDbecauseit’sgoingtolookdarkordimoutdoors.

7. Optional:UsingyourDMMsettoDCvoltsand“20,"measurethevoltageoftheLED.HowmanyvoltsdoestheLEDreceive?(Don’tforgettowrite“V”afterthenumberyouread.)

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8. SetyourDMMto“ohms”orthe“Ω”symbol.TouchoneprobetoeachsideoftheCdScell.Ifthisistoodifficult,thenattachanalligatorwiretoaprobeandtheotherendtooneofthewiresontheCdScell.Dothisforbothsides.Makesureyourdialissettomeasureresistance.Whatdoyouread?(Don’tforgettowrite“Ω”or“ohms”afterthenumberyouwritedown.)

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9. Fillinthedatatablebelow.Notethatyourvalueswillnotbethesameasmine,sinceyouhavedifferentlighting,differentbatteries,andadifferentsizecellthanIdo.Feelfreetogooutside,hideitunderthetable,closethecellinabook,putitnexttothewindow,etc…whentakingyourdata.Becreative!

CdSPhotocellDataTable

LightingCondition CdSCellResistance LEDVoltageCdSCellcompletelycoveredup

7.1MΩ(or7,100,000Ω) 0.5volts

Laserpointerbeamdeadcenteronthecell

3.8kΩ(or3,800Ω) 2.9volts


Reading

Thisisthefirstofmanydifferentburglaralarmswe’regoingtomakewithoursimplecircuitsandswitchesknowledge.Thisparticularoneisagoodonetostartwith,sinceit’srelativelysimpletomakeandyouprobablyhaveexperiencewiththebuzzyouhearwhenyouenterastorethat’sarmedwithoneofthese.

Aphotoresistororlightdependentresistorlimitstheamountofcurrentthatflowsthroughitinproportiontothelightitreceives.Thiseffectiscalledphotoconductivity.Themorelightthatfallsontheresistor,themoreelectricityflowsthroughthewire.Photoresistorsarealsocalledphotocells.

Exercises

1. HowisaCdScelllikeaswitch?Howisitnotlikeaswitch?

2. WhenistheLEDthebrightest?

3. Howcouldyouusethisasaburglaralarm?


Lesson#16:TripWireBurglarAlarm

Overview:Thisalarmhasathinwirethatsomeone“trips,"whichpullsoutthepaper,closesaswitch,andlightsuptheLED!

WhattoLearn:ThisparticularburglaralarmisanNC(NormallyClosed)switch,andtodayyougettolearnhowtowireitupinacircuitandpullthetrigger.

Materials

AAbatterycase 2AAbatteries 3alligatorclipwires woodclothespin 4‐6″pieceofsteelwire,likepicturehangerwireORuseun‐insulatedcopperwire 2unpaintedsteeltacksscrapofpaper LED

LabTime

1. MaketheNCtripwireswitch:a. Cuta3”pieceofsteelwire.Wrapthesteelwirearoundthestemofthetack.Dothistwice–oncefor

eachtack.b. Opentheclothespinalltheway,andinsertoneofthetacksinsidethejaw,likeyou’reinserting

teeth.Dothisfortheupperandlowerjawoftheclothespin.c. Orientthewiressothatonesteelwirecomesofftotheleftoftheclothespinandtheotherofftothe

right.Thiswillmakesurethatthewiresdon’ttouchduringyourexperiment.d. Openupyourpaperclip,andgrabascrapofasheetofpaper.Whenyoureleasetheclothespin,the

twometaltacksshouldbeoneithersideofthepaper.2. MaketheTripWireCircuit:

a. Useyourbatteries,wires,andLEDtomaketheLEDlightup.(Notripwireyet.)b. RemoveoneofthealligatorwiresfromtheLEDandreplaceitwithathirdalligatorwire.c. Attachoneofthefreealligatorwireendstooneofthesteelwirescomingfromtheclothespin.d. Attachtheremainingalligatorwiretothelaststeelwirefromtheclothespin.e. Yankthepaperaway–didtheLEDlightup?f. Attachstringtothepaper.Thelengthofstringyouneedisgoingtodependonwhereyouinstallthe

tripwirealarm.3. InstallationTip:Hidethisswitchdownlowbythedoorframeandusefishinglineinsteadofstringtomake

thisburglaralarmvirtuallyinvisible.Useatackintheframeortiethelinetothedoorhingetosecureandwaitfortheaction…


Reading

Doyouneedalittlehelpprotectingyourstuff,likefromyoungersiblingsornosyfriends?Thisburglaralarmreliesonaspecialkindofswitch:anNC(normallyclosed)switch.Thismeansthatwhentheswitchisjustsittingthere,itallowscurrenttoflow.Whenit’sactivated,electricitystops.TheoppositekindifswitchisanNO(normallyopen)switch,whichdoesn’tturnontheelectricityuntilyoupushthebutton.(TheburglaralarminthenextexperimentusesanNOswitch.)

Thisswitchworksbecausepaperdoesn’tconductelectricity–it’saninsulator,justlikeplastic.SincethetripwireisanNCswitch,thiscircuitworksuntilyoutriggertheswitch.Weneedawaytostopthecurrent(flowofelectrons)untilwewanttheLEDtoactivate.Whenyoustickthepaperindexcardbetweenthetwotacksintheclothespin,itbreakstheelectricalconnectionandtheswitchgoesintheOFFposition.RemovethepaperandyourswitchmovestotheONposition,andelectronsareflowingaroundandaroundyourcircuit,andyouseetheLEDlightup.

Thisisasilentalarm,butifyou’dlikealoudalarm,substituteabuzzerfortheLED.Makesuretoselectabuzzerthatislowvoltage(under6V),likeRadioShackpart#273‐053.

InstallationTip:Hidethisswitchdownlowbythedoorframeandusefishinglineinsteadofstringtomakethisburglaralarmvirtuallyinvisible.Useatackintheframeortiethelinetothedoorhingetosecureandwaitfortheaction…

Exercises

1. Howdoesthiswork?

2. Whattypeofswitchisthetripwire?

3. Namethreeplacesyoucaninstallthisalarm.


Lesson#17:PressureSensorOverview:You’veabouttomakeanNOburglaralarmswitch,whichissimilartotheTripWireBurglarAlarm,onlythisoneistriggeredbysqueezingit.Ifyou’reusingthespecialblackfoamwithoutthehole,itworksbecausethefoamconductsmoreelectricitywhensquishedtogether,andlesswhenit’satthenormalshape.

WhattoLearn:Switchescontroltheflowofelectricitythroughacircuit.Therearedifferentkindsofswitches.NC(normallyclosed)switcheskeepthecurrentflowinguntilyouengagetheswitch.TheSPSTandDPDTswitchesareNO(normallyopen)switches.Today’sswitchisalsoanNOswitch.

Materials

thinspongeorfoamsquare(about1″square) AAbatterycase 2AAbatteries 3alligatorclipwires 2largepaperclips scissors aluminumfoil LED

LabTime

1. MakethePressureSensor:a. Cutthefoilsoit’sslightlysmallerthanthefoamsquare.Youneedtwopieces.b. Carefullycutanopenholethroughthemiddleofyoursquare.Makeitbiggerthanyouthinkyou

need.c. Placeonepieceoffoilinthetopofthespongewiththeotherpieceonthebottom.d. Placeapaperclipontopofeachpieceoffoil.Pointthepaperclipsinoppositedirectionssothey

don’ttouchwhenyou’resqueezingthesensorlater.e. Wrapthewholethinginasinglepieceoftape.

2. MakethePressureSensorCircuit:a. Useyourbatteries,wires,andLEDtomaketheLEDlightup.(Notripwireyet.)b. RemoveoneofthealligatorwiresfromtheLEDandreplaceitwithathirdalligatorwire.c. Attachoneofthefreealligatorwireendstooneofthepaperclips.d. Attachtheremainingalligatorwiretotheotherpaperclip.e. Presshardonthesensor.GOTCHA!

3. Whenyousqueezethefoam,theLEDlightsup!It’sidealforunderadoormatorcarpetrugwherelotsofweightwilltriggerit.You’llalwaysknowwhenmom’sonherwayintoyourroom.

Troubleshooting:Thereareafewproblemareastowatchoutforwhenbuildingthissensor.First,makesuretheholeinyourfoamisbigenoughtostickafinger(orthumb)througheasily.Thefoamkeepsthefoilapartuntilsteppedon,thenitsquishestogethertoallowthefoiltomakecontactthroughthehole.Thesecondpotentialproblemisiftheswitchdoesn’tturntheLEDoff.Ifthishappens,itmeansyou’rebypassingtheswitchentirelyandkeepingthecircuitintheconstantONposition.Checkthetwofoilsquares,alligatorclips,andpaperclips–aretheytouchingaroundtheoutsideedges?Lastly,makesureyourfoamisthekindthatpopsbackintoshapewhenreleased.


BonusIdea:Stickjustthesensorunderarugandrunlongerwiresfromthesensortoyourroom.Whensomeonecomesdownthehallway,they’lltriggerthesensorandalertyoubeforetheygetthere!

Reading

Bycontrollinghowandwhenacircuitistriggered,youcaneasilyturnasimplecircuitintoaburglaralarm–somethingthatalertsyouwhensomethinghappens.Bysensinglight,movement,weight,liquids,evenelectricfields,youcantriggerLEDstolightandbuzzerstosound.Yourroomwillneverbethesame.

Thepressuresensorwe’rebuildingissmall,anditrequiresafairamountofpressuretoactivate.

Nowisagoodtimetointroducetheideaofpressure.Pressureisforce(likeweight)overagivenarea(likeafootprint).Ifyouweighed200pounds,andyourfootprintaveraged10”longand2”wide(sotheareaofyourfootprintis10x2=20squareinches),you’dexert200/20=10psi(poundspersquareinch)onthegroundwhenstandingonbothfeet.Or5psiperfoot.

However,ifyouwalkedaroundonstiltsinsteadoffeet,andthe”footprint”ofeachstiltaveraged1”by1”square,you’dnowexert200/(1x1)=200psi,or100psiperfoot.Whysuchadifference?

Thesecretisintheareaofthefootprint.Inourexample,yourfootisabout20squareinches,buttheareaofeachstiltwasonly1squareinch.Sinceyouhaven’tchangedyourweight,you’restillpushingdownwith200pounds.Inthestilts'case,you’repressingthesameweightintoamuchsmallerspot…andhencethepressureappliedtothesmallerareashootsupbyafactorof20.Imaginehowthefloorfeelsunderthespikeofahigh‐heeledshoe.

Sohowdoweusepressureinthisexperiment?Youneedtoexertpressureonthesensorforittoactivate.Howmuchpressureisgoingtodependonhowlargeorsmallyoursensoris,howstiffyourspongeis,howlargetheholeis,andsoforth.

BonusIdea:Stickjustthesensorunderarugandrunlongerwiresfromthesensortoyourroom.Whensomeonecomesdownthehallway,they’lltriggerthesensorandalertyoubeforetheygetthere!

Exercises

1. Howdoesthissensorwork?

2. WhatmakesthisanNOswitch?

3. Howcanyouuseboththetripwireandthepressuresensorinthesamecircuit?Drawitouthere:


Lesson#18:LatchingCircuits

Overview:Onceyou’vemadethePressureSensorburglaralarm,youmightbewonderinghowtomakethealarmstayonafterithasbeentriggered,thewaytheTripWireSensordoesnaturally.That’swhatwe’regoingtodotodayusinganothertypeofswitchandamorecomplexcircuit.

WhattoLearn:Arelayisaswitchyoucanturnonandoffusingelectricity.Itusesanelectromagnettoactivatetheswitchinsideofit.

Materials

relay(you’llwantonethathasacoilvoltageof12VDCorless) yourcompletedPressureSensorcircuit 3AAbatterypackswith6AAbatteries 7additionalalligatorclipwires Optional:SPSTswitch

LabTime

1. Hookupyourbatterypackslikethis:connectthepositiveleadfrombatterypack#1tothenegativeleadonbatterypack#2usinganalligatorclipwire.Connectthepositiveleadfrom#2tothenegativeof#3usingasecondalligatorwire.Youshouldnowhavetwofreeends:thenegativefrom#1andthepositivefrom#3.Thosearethetwoyouaregoingtousetopoweryourrelayinthenextstep.(IfyouuseyourDMMsetto20voltsandDC,you’llfindyouhaveabout9Vbetweenthosetwoleads.That’susuallyenoughtogettherelaytoclick.

2. Connectthealligatorleadfrombatterypack#1toonesideoftherelaycoil.Thecoilterminalsareusuallythetwotabsthatareorientateddifferentlythantherest.Touch(don’tconnect)thealligatorleadfrombatterypack#3totheothercoilterminal.Tapitafewtimestoheartherelayclick.Ifyoudon’tgetaclick,stopandredoyourwiringuntilyoudobeforemovingon.

3. Connectthealligatorclipleadfrombatterypack#3(inthevideo,it’swhite)toonesideoftheSPSTswitch.YoucanuseyourindexcardSPSTswitchifyoulike,orsimplyskiptheswitchandconnectittoafreealligatorcliplead(inthevideo,thisoneisyellow).

4. Connecttheswitchtothepressuresensorusinganotheralligatorcliplead(yellowinthevideo).5. Connecttheotherpaperclipofthepressuresensortotherelaycoil(asecondwhitewireinthevideo).6. Connecttheothersideoftherelaycoiltothebatteries(inthevideo,it’sgreen).7. Recheckyourconnections:YoushouldhavetherelayconnectedtotheSPSTtothepressuresensorand

backtotherelay,likeabigloop.8. Squeezethepressuresensor–doyouheartherelayclickonce?Ifnot,redosteps#3‐9.9. Thevideousesabuzzer.YoucanuseyourLEDinstead(it’samuchquieterlabifyoudo).Connectone

alligatorwiretoeachleadoftheLED(inthevideo,theyaregreenandwhite).ConnecteachofthealligatorwiresfromtheLEDtothecoil,oneoneachterminal,rightontopoftheonesthatarealreadyclippedon.

10. Connectafreshalligatorclipleadtoonesideofthepressuresensorrightontothepaperclip(redwireinthevideo).Theothersideofthisalligatorclipgoestothemiddlecontactontherelay.


11. Connectanothernewalligatorclipleadtoeitherthetoporthebottomcontact.Here’showtotellwhichone:lookatyourrelay.Doyouseewhichcontact(toporbottom)thesmallmetalleveristouchingwhenit’snotactivated?That’snottheoneyouwant.Choosetheotheroneandclipthewireontothatterminal.Theotherendofthisalligatorwire(whiteinthevideo)goestotheothersideofyourpressuresensorrightontothepaperclip.Youshouldhavetwowiresoneachpaperclip.

12. PressthesensortotriggertheLED,andtherelayshouldalsoclickon.DoestheLEDstaylit?Ifnot,gobackandtryhookingupyourcircuitagain,carefullyfollowingthestepsinthevideo.

Reading

Arelayisswitchyoucanturnonandoffusingelectricity.Itusesanelectromagnettoactivetheswitchinsideofit.We’lltalkmoreabouthowtherelayworkswhenwediscussMagnetism.

Onceyou’vemadethePressureSensorburglaralarm,youmightbewonderinghowtomakethealarmstayonafterithasbeentriggered,thewaytheTripWireSensordoesnaturally.

Thereasonthisisn’tassimpleasitseemsisthatthetripwireisanormallyclosed(NC)switchwhilethepressuresensorisanormallyopen(NO)switch.Thismeansthatthetripwireisdesignedtoallowcurrenttoflowthroughthetackswhenthere’snopaperinsulatingthem,whilethepressuresensorstopscurrentflowinginitsun‐squishedstate.It’sjustthenatureofthetwodifferenttypesofswitches.

However,wecanbuildacircuitusingarelaywhichwill”latchon”whenactivatedandremainonuntilyouresetthesystem(bycuttingoffthepower).Thissuper‐coollatchingcircuitvideowillshowyoueverythingyouneedtoknow

Exercises

1. Whatisarelay?

2. Whatdoestherelaydointhiscircuit?

3. Drawoutapicturethatshowshoweverythingisconnectedinyourcircuit:


Lesson#19:NerveTesterOverview:Today’slessonismostlyplaytime,sinceyoualreadyknoweverythingyouneedtoinordertocreatethisproject.You’regoingtostartwithasimplecircuit,thenmodifyitabitandturnitintoanelectricalrollercoaster.

WhattoLearn:Howtomodifyyoursimplecircuitintosomethingfunandentertaining!Andprobablyhoneyourtroubleshootingskillswhenthingsgowrong.

Materials

AAbatterycase 2AAbatteries 2alligatorwires LED barewireORyoucanuseawirecoathanger,butbeawareyoumayhavetousesandpaperifit’siscoated

withclearenamel popsiclestick paperclip tape woodblockwithwood2woodscrewsandadrilland/orscrewdriverORdensefoamblock

LabTime

1. InsertbatteriesintocasesandconnectanLEDsothatitworks.Setasideasyoumakethenextpart.2. Usingapaperclip,formaloopandsecuretoapopsiclesticksothatitlookslikeabubblewand,withthe

endspokingoutofthebottomofthetape.Bendtheendsupsoyoucanclipontothemwithyouralligatorclipslater.(Youshouldhave¼–½”pokingupward.)

3. Bendandtwistanun‐insulatedcoathangerwireintospiralsanddizzyroller‐coastershapes.Whenyou’vegotitright,makeasmallloopateachend.Ifyou’reusingawoodbase,insertonescrewintoeachsmallloopandscrewintothewoodbase,about10”apart(besuretothreadthebubblewandloopontothewirefirst!).Yourrollercoasterwireshouldstanduponitsown.

4. Disconnecttheclipleadwirefromyourpositivebatteryterminalandclipittotheexposedpaperclipendonyourpopsicle‐stickbubble‐wand.Wraptheexposedendofthepositiveterminalaroundoneendofthecoathangernearthescrewandsealwithtape.

5. Ifitdoesn’twork:a. Makesurethebatteriesarefreshandinsertedtherightway.b. Makesureyourcoathangerisreallyjustabarerodofmetal.Ifit’sgotacoatingonit,you’llneedto

usesandpaperontheentirelengthbeforeusingitintheproject.c. Useablockofwoodorfoamforbestresults…theyarebothexcellentinsulatorsforthewiretrack.d. Placeswherekidsmostoftenforgettohookup:

i. connectthewiretoabarespotonthetrackitself,nearthebaseii. besureyourloopalsohasagoodmetalwireconnection


Reading

Electricalcircuitsareusedforallkindsofapplications,fromblenderstohairdryerstocars.Andgames!Here’saquickandeasygameusingtheprinciplesofconductivity.Thisexperimentisatestofyournervesandskilltoseeifyoucancompletetherollercoastercircuitandmakeitfromoneendtotheother.Youcanopttomakeanoisyversion(morefun)orasilentversion(forstealth).

Exercises

1. Canyoutraveltheentirepathwithoutturningonthelight?

2. Whereinyourcircuitcanyouaddaswitchtoturnthegameonandoff?


ElectricityEvaluation

StudentWorksheet

Overview:Todayyou’regoingtotaketwodifferenttests:thequizandthelabpractical.You’regoingtotakethewrittenquizfirst,andthelabpracticalattheendofthislab.Thelabpracticalisn’tapapertest–it’swhereyougettoshowyourteacherthatyouknowhowtodosomething.

LabTest&Homework

1. Yourteacherwillcallyouupsoyoucansharehowmuchyouunderstandaboutelectricityandhowitworks.Sincescienceissomuchmorethanjustreadingabookorcirclingtherightanswer,thisisanimportantpartofthetesttofindoutwhatyoureallyunderstand.

2. Whileyouarewaitingforyourturntoshowyourteacherhowmuchofthisstuffyoualreadyknow,yougettochoosewhichhomeworkassignmentyouwanttocomplete.Theassignmentisduetomorrow,andhalfthecreditisforcreativityandtheotherhalfisforcontent,soreallyletyourimaginationflyasyouworkthroughit.Chooseonethatyoudidn’tchoosefromtheStaticElectricityhomeworkassignmentlasttime:a. Writeashortstoryorskitaboutelectricityfromtheperspectiveofthewireortheelectrical

component.You’llreadthisaloudtoyourclass.b. Makeaposterthatteachesthemainconceptstoelectricity.Whenyou’refinished,you’lluseittoteach

toaclassintheyoungergradesanddemonstrateeachoftheprinciplesthatyou’velearned.c. Writeandperformapoemorsongaboutelectricity.Thiswillbeperformedtoyourclass.


ElectricityQuiz

Name______________________________________________________

1. Whatisthedifferencebetweenaboltoflightningandtheelectricityinyourcircuit?

2. Howdoeselectricitypassthroughamaterial?

3. Whatkindsofmaterialsareconductorsandinsulators?Namethreeofeach.a. Conductor:b. Conductor:c. Conductor:

d. Insulator:e. Insulator:f. Insulator:

4. WhatisanNCSPSTswitch?Howdoesitworkwhenplacedinacircuit?

5. What'sthedifferencebetweenanincandescentlightbulb,afluorescentlight,andtheLED?

6. Ifyoumeasure2.85voltsfromyourbatterypack,doyouneednewbatteriesorwilltheywork?

7. Wherehaveyouusedpotentiometersineverydaylife?


8. HowisaCdScelllikeaswitch?Howisitnotlikeaswitch?

9. IsthetripwireanNOorNCswitchwithoutthepaperinserted?

10. Whatisarelay?

11. Imagineyourteacherjustaskedyoutohookupasimplecircuittopoweramotor.Drawthecircuitasadiagrambelow,andshowhowelectricityflowsthroughyourcircuit(indicatethedirectionwithanarrow).Labeleverypartofyourdiagram,includingeverycomponentused.Forbonuspoints,alsoshowwhereyouwouldputyourDMMprobestomeasurehowmuchvoltagethemotorisreceiving.


ElectricityLabPracticalStudentWorksheet


Materials:

AAbatterycase 2AAbatteries 4alligatorwires switch LED 1.5‐3VDCmotor

LabPractical:

DesignandbuildasimpleseriescircuitwhichlightsupanLEDandincludesaswitch.

DesignandbuildasimpleparallelcircuitwhichpowersbothLEDandmotoratthesametime.

Explainhowelectricalenergycanbeconvertedtolightormotion.


Section3:Electrochemistry

Whenelectriccurrentpassesthroughamaterial,itdoessobyelectricalconduction.Therearedifferentkindsofconduction,suchasmetallicconduction,whereelectronsflowthroughaconductor(likemetal)andelectrolysis,wherechargedatoms(calledions)flowthroughliquids.

Whenanatom(likehydrogen)ormolecule(likewater)losesanelectron(negativecharge),itbecomesanionandtakesonapositivecharge.Whenanatom(ormolecule)gainsanelectron,itbecomesanegativeion.Anelectrolyteisanysubstance(likesalt)thatbecomesaconductorofelectricitywhendissolvedinasolvent(likewater).

Thistypeofconductoriscalledan“ionicconductor”becauseoncethesaltisinthewater;ithelpsalongtheflowofelectronsfromoneclipleadterminaltotheothersothatthereisacontinuousflowofelectricity.


Lesson#20:Electrolytes

Overview:Electricity.Chemistry.Nothingincommon,havenothingtodowitheachother…right?Wrong!Electrochemistryhasbeenafactsince1774.Onceelectricitywasappliedtoparticularsolutions,changesoccurredthatscientistsofthetimedidnotexpect…andyougettoplaydetectiveagainandfigureoutwhat’sgoingon.

WhattoLearn:Anelectrolyteisanysubstance(likesalt)thatbecomesaconductorofelectricitywhendissolvedinasolvent(likewater).Thistypeofconductoriscalledan”ionicconductor”becauseoncethesaltisinthewater,ithelpsalongtheflowofelectronsfromoneclipleadterminaltotheothersothatthereisacontinuousflowofelectricity.

Materials

2AAbatteries AAbatterycase 3alligatorclipwires LED Water Sugar Salt Vinegar Bakingsoda Lemonjuice Oil Soap 10disposablecups 10popsiclesticksforstirring Optional:DMM

LabTime

1. Connectthealligatorclipleadstothewiresfromthebatterycase,oneoneach.2. ConnecttheotherendstotheLEDtomakeasimplecircuit.Thismakessureeverythingisworkingbefore

tryingsomethingnew.3. DisconnectoneofthewiresfromtheLEDandinsertathirdalligatorwire.4. Touchthetwofreeendsofthealligatorclipleadstogether.TheLEDshouldlightup.5. Fillthejarwithwater.6. Insertthefreeendsofthealligatorclipleadsintothejar.Whathappened?Writeithere:

___________________________________________________________________________________________________

7. Addacoupletablespoonsofsaltandstir.


8. Insertthefreeendsofthealligatorclipleadsintothejar.Whathappened?Writeithere:___________________________________________________________________________________________________

9. Optional:TurnontheDMMto“20”voltsDCandinserttheprobesintothejar.Howmuchvoltagedoyouread?______________________________________________

10. Filloutthedatatable.11. Whenyou’vegotacoupleofminutesoflabtimeleft,askyourselfthisquestion:Whathappensifyoumixan

electrolyteandnon‐electrolytetogether?Testitandrecordyourresultsinthelastboxonthedatatable.12. Cleanup:Cleaneverythingthoroughlyafteryouarefinishedwiththelab.Aftercleaningwithsoapand

water,rinsethoroughly.Chemistsusetheruleof“three”incleaningglasswareandtools.Afterwashing,chemistsrinseoutallvisiblesoapandthenrinsethreetimesmore.

13. Storage:Placeallchemicals,cleanedtools,andglasswareintheirrespectivestorageplaces.14. Disposal:Disposeofallsolidwasteinthegarbage.Liquidscanbewasheddownthedrainwithrunning

water.Letthewaterrunawhiletoensurethattheyhavebeendilutedandsentdownstream.


ElectrolyteDataTableSubstanceTested Diditconductelectricity? Howmuchvoltageispresent?

PlainWater

Water+Salt

Electrolyte:Non‐electrolyte:

15. Whenyou’vegotacoupleofminutesoflabtimeleft,runonemoretest,andyou’llrecordyourresultinthelastboxonthedatatable.


Reading

Ourfirstpartoftheexperimentusesasaturatedsolutionoftablesaltthatisjustsittinginacontainermindingitsownbusiness.

Thebatteriespushvoltagethroughthesaltwater.Thatelectriccurrenttearsthesodiumfromthechlorine.Thesepositivelyandnegativelychargedionsrushabout,lookingforsomethingtheyareattractedto.Oppositesattract,sopositivelychargedsodiumionsfindspendingtimewiththenegativeelectrodeatreat.Theyareveryhappytogether.Negativelychargedchlorineionsareattractedtothepositiveelectrode.

Sodiumchloridedecomposesintosodiumandchlorineions:NaCl–>Na++Cl‐

Whenthesaltsodiumchloride(NaCl)mixeswithwater,itseparatesintoitspositively(Na+)andnegatively(Cl‐)chargedparticles(ions).Whenasubstancemixeswithwaterandseparatesintoitspositiveandnegativeparts,it’scalleda”salt.”

Saltscanbeanycoloroftherainbow,fromthedeeporangeofpotassiumdichromatetothevividpurpleofpotassiumpermanganatetotheinkyblackofmanganesedioxide.DidyouknowthatMSG(monosodiumglutamate)isasalt?Mostsaltsarenotconsumable,asintheleadpoisoningyou’dgetifyouingestedleaddiacetate.

Ifyoupassacurrentthroughthesolutionofsaltandwater,oppositesattract:thepositiveionsareattractedtothenegativepoleandthenegativeionsgotowardthepositivepole.Thesemigrationsionsallowelectricitytoflow,whichiswhy”salt”solutionsconductelectricity.

Exercises

1. Whydoeselectricityflowthroughsomesolutionsbutnotallofthem?

2. Whatisasalt?

3. Howareelectrolytesusedtodayinreallife?

4. Whichsubstancewasyourtopconductor?

5. Whichsubstancedidn’tconductanythingatall?

6. Whathappensifyoumixanelectrolyteandnon‐electrolytetogether?


Lesson#21:Electrolysis

Overview:Thislabisalotoffun,becausewe’rebreakingapartmoleculesandsettingthemonfire.Paycloseattentiontohowtodothisonesafelysoyoureyebrowsstayattached.

WhattoLearn:Awatermoleculeistwohydrogenatomsandoneoxygenatom.You’regoingtouseelectricitytosplitapartthewatermoleculeintosmallerpieces:hydrogenions(positivelychargedhydrogen)andoxygenions(negativelychargedoxygen).Thepositivehydrogenionszipovertothenegativeterminalandformtinybubblesrightonthewire.Samethinghappensonthepositivebatterywire.Afterabitoftime,theionsformalargergasbubble.

Materials

2testtubes,glassorplastic 2alligatorclipleads 1disposablecup Distilledwater One9voltbatterywithbatteryclip Saltorsodiumsulfate

LabTime:Havefunandpleasefollowthedirectionscarefully.Thiscouldbedangerousifyou’renotcareful.

1. Havefunandpleasefollowthedirectionscarefully.Thiscouldbedangerousifyou’renotcareful.2. Fillthecuptwo‐thirdswithwater.3. Fillyourtesttubeswithwater.Placeyourthumbovertheend,andinvertandinsertintothewatercup.

Youwantanentiretesttubefilledwithwater.Dothisforbothtesttubes.Afewbubblesareokay.4. Connectyourbatterytotwoalligatorclipleads,oneleadforeachterminal.5. Insertonealligatorclipintoeachtesttube.6. Youshouldnowhavetwoinvertedtesttubesfilledwithwater,eachwiththeirownalligatorclipwire.7. Putatablespoonorsoofsaltintothewaterandstiritup.Thesaltallowstheelectricitytoflowbetter

throughthewater.Ifyouhaveaccesstosodiumsulfate,useit,asthereactionwillprogressfaster.8. Youshouldseebubblesrisingintothetesttube.Ifyoudon’tseebubbles,checkthewiresandbattery

connection.9. Whenthetesttubeismostlyfullofgas,askanadulttotestforflammability.Beforetheydo,whichtubedo

youthinkisfilledwithoxygenandwhichishydrogen?Writedownyourguesshere:a. Positivewire:_________________________________________

b. Negativewire:_________________________________________

10. Whatdidyoureallyfind?a. Positivewire:_________________________________________

b. Negativewire:_________________________________________


11. Cleanup:Cleaneverythingthoroughlyafteryouarefinishedwiththelab.Aftercleaningwithsoapandwater,rinsethoroughly.Chemistsusetheruleof“three”incleaningglasswareandtools.Afterwashing,chemistsrinseoutallvisiblesoapandthenrinsethreetimesmore.

12. Storage:Placeallchemicals,cleanedtools,andglasswareintheirrespectivestorageplaces.13. Disposal:Disposeofallsolidwasteinthegarbage.Liquidscanbewasheddownthedrainwithrunning

water.Letthewaterrunawhiletoensurethattheyhavebeendilutedandsentdownstream.

Reading

Ifyouguessedthatthishastodowithelectricityandchemistry,you’reright!Butyoumightwonderhowtheyworktogether.Backin1800,WilliamNicholsonandJohannRitterwerethefirstonestosplitwaterintohydrogenandoxygenusingelectrolysis.(Soonafterward,Ritterwentontofigureoutelectroplating.)Theyaddedenergyintheformofanelectriccurrentintoacupofwaterandcapturedthebubblesformingintotwoseparatecups,oneforhydrogenandtheotherforoxygen.

Ittakesenergytosplitawatermolecule.(Ontheflipside,whenyoucombineoxygenandhydrogentogether,itmakeswaterandapuffofenergy.That’swhatafuelcelldoes.)Backtosplittingthewatermolecule–astheelectricityzipsthroughyourwires,thewatermoleculebreaksapartintosmallerpieces:hydrogenions(positivelychargedhydrogen)andoxygenions(negativelychargedoxygen).Rememberthatabatteryhasaplusandaminuschargetoit,andthatpositiveandnegativeattracteachother.

So,thepositivehydrogenionszipovertothenegativeterminalandformtinybubblesrightonthewire.Samethinghappensonthepositivebatterywire.Afterabitoftime,theionsformalargergasbubble.Ifyoustickatesttubeovereachwire,youcancapturethebubblesandwhenyou’reready,igniteeachtoverifywhichiswhich.

Ifthematchburnsbrighter,thegasisoxygen.IfyouhearaPOP!,thegasishydrogen.Oxygenitselfisnotflammable,soyouneedafuelinadditiontotheoxygenforaflame.Inonecase,thefuelishydrogen,andhenceyouhearapopasitignites.Intheothercase,thefuelisthematchitself,andtheflameglowsbrighterwiththeadditionofmoreoxygen.

Whenyouputthematchtoit,theenergyoftheheatcausesthehydrogentoreactwiththeoxygenintheairand“POP,”hydrogenandoxygencombinetoformwhat?That’sright,morewater.Youhavedestroyedandcreatedwater!(It’saverysmallamountofwater,soyouprobablywon’tseemuchchangeinthetesttube.)

Thechemicalequationsgoingonduringthiselectrolysisprocesslooklikethis:

Areductionreactionishappeningatthenegativelychargedcathode.Electronsfromthecathodearestickingtothehydrogencationstoformhydrogengas:

2H+(aq)+2e‐‐‐>H2(g)

2H2O(l)+2e‐‐‐>H2(g)+2OH‐(aq)

Theoxidationreactionisoccurringatthepositivelychargedanodeasoxygenisbeinggenerated:

2H2O(l)‐‐>O2(g)+4H+(aq)+4e‐


4OH‐(aq)‐‐>O2(g)+2H2O(l)+4e‐

Overallreaction:

2H2O(l)‐‐>2H2(g)+O2(g)

Notethatthisreactioncreatestwicetheamountofhydrogenasoxygenmolecules.Ifthetemperatureandpressureforbotharethesame,youcanexpecttogettwicethevolumeofhydrogentooxygengas.(Thisrelationshipbetweenpressure,temperature,andvolumeistheIdealGasLawprinciple.)

Thisistheideabehindvehiclesthatrunonsunlightandwater.Theyuseasolarpanel(insteadofa9Vbattery)tobreakapartthehydrogenandoxygenandstoretheminseparatetanks,thenrunthembothbacktogetherthroughafuelcell,whichcapturestheenergy(releasedwhenthehydrogenandoxygenrecombineintowater)andturnsthecar’smotor.Cool,isn’tit?

Exercises

1. Whyarebubblesforming?

2. Didbubblesformatbothwires,oronlyone?Whatkindofbubblesarethey?

3. Whatwouldhappenifyoudidthisexperimentwithplainwater?Woulditwork?Whyorwhynot?

4. Whichterminal(positiveornegative)producedthehydrogengas?

5. Didthereactioncreatemorehydrogenormoreoxygen?


Lesson#22:Electroplating

Overview:Peopleusethistechniquetoaddmaterialtoundersizedparts,forplacingaprotectivelayerofmaterialonobjects,andtoaddaestheticqualitiestoanobject.

WhattoLearn:You’regoingtouseelectrolytestodepositmetalionsandmakethemsticktoobjectsbyusingbypositiveandnegativeelectricalcharges.

Materials

oneshinymetalkey(askfortheseatahardwarestorethatmakeskeysandkeepsabucketofmistakes) copperstrip,copperpipeorshinycopperpenny(shineitupwithketchupandatoothbrush) 2alligatorclips 9Vbatterywithclip water coppersulfate disposablecup papertowel popsiclestick

LabTime

1. Wipeyourkeywithafewswipesofawetpapertoweltogetridoftheoilsanddirtfromyourfingers.2. Brushupyourpennyorcopperpipeuntilit'sshiny.Youcanusesandpaperoracleanpapertowel.3. Placeateaspoonofcoppersulfateintoyourcontainer.Don’ttouchthischemicalwithyourhands.Capit

andsetitaside.4. Addathinstreamofwater,justenoughsothatthebitsonthebottomdissolve.Goslowlyandstir

continuouslyuntilallthecoppersulfateisdissolved.(Donotheatthesolution.)5. Connectthewirestoyourbattery.6. Connectoneendofanalligatorwiretothecopperstripandtheotherendtothepositive(red)wirefrom

yourbattery.7. Connecttheotheralligatorwiretothekeyandthenegative(black)lead.8. Placethecopperstripandthekeyinthesolutionwithouttouchingeachother.Iftheytouch,you’llshort

yourcircuitandblowupyourbattery.Letthissitforafewminutes…andnoticewhathappensandhowlongittooktohappen(glanceattheclockwhenyouputthewiresinthesolution).Writedownyourobservations.

9. Workingwithanotherlabgroup,useasecondbatteryinyourcircuit.a. Connectthebatteriesinseries:connectthesecondbatterybyremovingthewireattachedtothe

positiveterminaloftheoriginalbattery,andattachingathirdalligatorcliplead.Theotherendofthisalligatorclipleadgoestothenewbattery’snegativeterminal.Reattachtheclipleadtothenewpositiveterminalandperformyourexperiment.Doesthereactionhappenfasterorslowernow?


b. Connectthebatteriesinseries:twisttogethertheredwiresfrombothbatteries.Twistthenegativewiresfromboth.Nowinsertthiswheretheoriginalbatterywasinyourcircuitusingalligatorclipleads.Doesthereactionhappenfasterorslowernow?

10. Removethekeyandthecopperstripfromthesolutionandsetonthepapertowel.Attachonepapercliptoeachleadandputthem(withouttouching)inthesolution.Whathappens?

11. Completethedatatable.Besuretonotewhatkindofcopperpieceyouused,andhowmanybatterieswereinyourcircuit.Ifyouhadmorethanonebattery,alsoincludehowtheywereconnected(seriesorparallel).For“TimetoElectroplate,"youcanentertwonumbers:firstnumberisthetimethatyoufirstputthewiresintowhenyoufirststarttoseeacolorchangebeginningtoappear.Thesecondnumberishowlongittooktoelectroplatethewholething,measuredwhenyoutookitoutofthesolution.

ElectroplatingDataTablePositiveElectrode NegativeElectrode Timeto

ElectroplateBattery Notes/Observations


12. Cleanup:Cleaneverythingthoroughlyafteryouarefinishedwiththelab.Aftercleaningwithsoapandwater,rinsethoroughly.Chemistsusetheruleof“three”incleaningglasswareandtools.Afterwashing,chemistsrinseoutallvisiblesoapandthenrinsethreetimesmore.

13. Storage:Placeallchemicals,cleanedtools,andglasswareintheirrespectivestorageplaces.14. Disposal:Disposeofallsolidwasteinthegarbage.Strainoutthesolutionthroughapieceofpapertowel

andthrowthepapertowelinthetrash.Liquidscanbewasheddownthedrainwithrunningwaterorflusheddownthetoilet.Ifusingasink,letthewaterrunawhiletoensurethattheyhavebeendilutedandsentdownstream.

Reading

ElectroplatingwasfirstfiguredoutbyMichaelFaraday.Thecopperdissolvesandshootsovertothekeyandgetsstuckasathinlayerontothemetalkey.Duringthisprocess,hydrogenbubblesupandisreleasedasagas.Peopleusethistechniquetoaddmaterialtoundersizedparts,forplacingaprotectivelayerofmaterialonobjects,andtoaddaestheticqualitiestoanobject.

Thisexperimentcanbetricky.Theproblemareasinclude:

1. Solutionisnotsaturated,meaningthere’stoomuchwatermixedin.Ifthishappens,addmorecoppersulfate.

2. Wiresaren’tmakinggoodcontactwiththebatteryormetalpieces.3. Notenoughvoltageorampsavailabletodrivethecircuit.Ifthishappens,youcanaddasecondbatteryto

yourcircuiteitherinseriesorparallel.4. Nocoppersulfate?Youcanusesaltandvinegar,althoughthisisamuchslowerreactionandyou’ll

probablywanttoleaveitforacoupleofhours.

Exercises

1. Lookatyourkey.Whatcolorisit?

2. Wheredidthecopperonyourkeycomefrom?

3. Whathappenedwhenyouaddedasecondbattery?

4. Whichcircuit(seriesorparallel)didthereactionacceleratefasterwith?


Lesson#23:FruitBattery

Overview:Todayyougettoraidtherefrigeratorandtestseveraldifferentkindsoffruitsandveggiestocreatethebestbatterywiththehighestvoltage.Donoteatanythingthatwasusedinthelab.

WhattoLearn:Thisexperimentshowshowabatteryworksusingelectrochemistry.Thecopperelectronsarechemicallyreactingwiththelemonjuice,whichisaweakacid,toformcopperions(cathode,orpositiveelectrode)andbubblesofhydrogen.Thesecopperionsinteractwiththezincelectrode(negativeelectrode,oranode)toformzincions.Thedifferenceinelectricalcharge(potential)onthesetwoplatescausesavoltage,whichkidswillmeasurewithyourdigitalmulti‐meter.

Materials

zincstrip copperstrip twoalligatorwires digitalmultimeter(DMM)

Youcanuseagalvanizednailandacopperpenny(preferablymintedbefore1982)foradditionalelectrodesandconnectthemallthewayaroundthefruit.

Fruittoexperimentmayinclude:

lemon lime apple potato tomato bananas grapes pineapple oranges tangerines

LabTime

1. Rollandsquishthelemonaroundinyourhandsoyoubreakupthemembranesinside,withoutbreakingtheskinorleakinganyjuice.Ifyou’reusingnon‐membranefoods,suchasanappleorpotato,youareallreadytogo.

2. Insertthecopperandzincstripsintothelemon,makingsuretheydonotcontacteachotherinside.3. Cliponetestwiretoeachmetalstripusingalligatorwirestoconnecttothedigitalmultimeter.4. TurnontheDMMto20VDC.Readthemultimeterandrecordyourresultsinthedatatable.5. Whathappenswhenyougentlysqueezethelemon?Doesthevoltagevaryovertime?6. Fillinthedatatableasyoutestthesedifferentideas:

a. Trypotatoes,apples,orotherfruitorvegetablecontainingelectrolytes.Recordyourmeasurementsinthedatatable.

b. Whatifyouuseoneelectrodeinonefruitandoneintheother?Whatdoyoumeasure?


FruitBatteriesDataTable

Trial# FruitType VoltsGenerated(V)

1

2

3

4

5

6

7

8

9

10

Reading

Thebasicideaofelectrochemistryisthatchargedatoms(ions)canbeelectricallydirectedfromoneplacetoanother.Ifwehaveaglassofwateranddumpinahandfulofsalt,theNaCl(salt)moleculedissociatesintotheionsNa+andCl‐.

Whenweplunkinonepositiveelectrodeandonenegativeelectrodeandcrankupthepower,wefindthatoppositesattract:Na+zoomsovertothenegativeelectrodeandCl‐zipsovertothepositive.Theionsareattracted(directed)totheoppositeelectrodeandthereiscurrentinthesolution.

Electrochemistrystudieschemicalreactionsthatgenerateavoltageandviceversa(whenavoltagedrivesachemicalreaction),calledoxidationandreduction(redox)reactions.Whenelectronsaretransferredbetweenmolecules,it’saredoxprocess.


Fruitbatteriesuseelectrolytes(solutioncontainingfreeions,likesaltwaterorlemonjuice)togenerateavoltage.Thinkofelectrolytesasamaterialthatdissolvesinwatertomakeasolutionthatconductselectricity.Fruitbatteriesalsoneedelectrodesmadeofconductivematerial,likemetal.Metalsareconductorsnotbecauseelectricitypassesthroughthem,butbecausetheycontainelectronsthatcanmove.Thinkofthemetalwirelikeahosefullofwater.Thewatercanmovethroughthehose.Aninsulatorwouldbelikeahosefullofcement–nochargecanmovethroughit.

Youneedtwodifferentmetalsinthisexperimentthatareclose,butnottouchinginsidethesolution.Ifthetwometalsarethesame,thechemicalreactiondoesn’tstartandnoionsflowandnovoltageisgenerated–nothinghappens.

Thisexperimentproducesaroundonevoltofelectricity,andtheampsareinthemicro‐to‐milliscale.Forcomparison,you’llneedabout557lemonstolightastandardflashlightbulb.

Exercises

1. Whatkindsoffruitmakethebestbatteries?

2. Whathappensifyouputoneelectrodeinonefruitandoneelectrodeinanother?

3. Whathappensifyoustickmultipleelectrodepairsaroundapieceoffruit,andconnecttheminseries(zinctocoppertozinctocoppertozinc…etc.)andmeasurethevoltageatthestartandendelectrodes?


Lesson#24:SaltyBatteryOverview:Inthelastexperiment(FruitBatteries),weexperimentedwithdifferentelectrolytesolutionsfortheelectrodes.Thistime,we’rekeepingthesolutionthesame,butchangingtheelectrodes.

WhattoLearn:Thebasicideaofelectrochemistryisthatchargedatoms(ions)canbeelectricallydirectedfromoneplacetotheother.Ifwehaveaglassofwateranddumpinahandfulofsalt,theNaCl(salt)moleculedissociatesintotheionsNa+andCl‐.Whenweplunkinonepositiveelectrodeandonenegativeelectrodeandaddelectricity,wefindthatoppositesattract:Na+zoomsovertothenegativeelectrodeandCl‐zipsovertothepositive.Theionsareattracted(directed)totheoppositeelectrodeandthereiscurrentinthesolution.

Materials

water salt distilledwhitevinegar Gogglesandglovesifyouhaveanadultto

handlebleach(donothandlethisyourself–youradultwilldothispartforyou)

Disposablecup Popsiclestick

Electrodestoexperimentmayinclude: realsilverware(notstainless) shinynail(galvanized) dullnail(iron) woodscrew(brass) largepaperclip copperpennyorcopperpipe graphitefrominsideapencil 2alligatorwires digitalmultimeter(DMM)

LabTime

1. Fillyourcuppartwaywithwater.2. Addateaspoonofvinegar.3. Addateaspoonofsalt.4. Optional:addacoupleofdropsofbleach,capitandputitawayoutofreachofkids.Ifyouareusingbleach,

makesureeverykidiswearingapairofgoggles.5. Connectthenailwithonealligatorcliplead.6. Connectthepennywithanotheralligatorcliplead.7. Dipbothnailandpennyinthewater,andmakesuretheyarenottouchingeachother.8. ConnecttheotherendsofalligatorclipleadstotheprobesontheDMM,onealligatorwiretoeachprobe.9. TurnontheDMMto20VDC.Whatdoyouread?Writeithere:_____________________________________________10. Whathappensifyoupullthetwoelectrodesasfarapartfromeachotheraspossible?Whathappensto

yourvoltage?Writeithere:

_____________________________________________________________________________________________


11. Replacethepennywithapaperclip,anddipitinthesolution.Whatdoyouread?Writeitinyourdatatable.12. Whataboutabrassscrew?Whatotherthingscanyoutry?Whatdifferentcombinationsaretheretotest?

Fillinthedatatablewithyourmeasurements.

Reading

Usingoceanwater(ormakeyourownwithsaltandwater),youcangenerateenoughpowertolightupyourLEDs,soundyourbuzzers,andturnamotorshaft.We’llbetestingoutanumberofdifferentmaterialssuchascopper,aluminum,brass,iron,silver,zinc,andgraphiteinasmallsampleofsaltwatertofindoutwhichworksbestforyoursolution.

Electrochemistrystudieschemicalreactionsthatgenerateavoltageandviceversa(whenavoltagedrivesachemicalreaction),calledoxidationandreduction(abbreviated”redox”)reactions.Whenelectronsaretransferredbetweenmolecules,it’saredoxprocess.

Electrolytes(asolutioncontainingfreeions,likesaltwaterorlemonjuice)canbeusedtogenerateavoltage.Thinkofelectrolytesasamaterialthatdissolvesinwatertomakeasolutionthatconductselectricity.DidyounoticehowinLesson#23:FruitBatteries,wealsoneededelectrodesmadeofconductivematerial,likemetal?Metalsareconductorsnotbecauseelectricitypassesthroughthem,butbecausetheycontainelectronsthatcanmove.Thinkofthemetalwirelikeahosefullofwater.Thewatercanmovethroughthehose.Aninsulatorwouldbelikeahosefullofcement–nochargecanmovethroughit.Youneedtwodifferentmetalsinthisexperimentthatareclose,butnottouchinginsidethesolution.Ifthetwometalsarethesame,thechemicalreactiondoesn’tstartandnoionsflow,novoltageisgenerated…nothinghappens.Butdon’ttakemywordforit–tryitforyourself!

Exercises

1. Whichcombinationgivesthehighestvoltage?

2. Whathappensifyouusetwostripsofthesamematerial?

3. Whatwouldhappenifweusednon‐metalstrips?


SaltyBatteryDataTable

Trial# Electrode#1 Electrode#2 Voltage(V)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20


Lesson#25:SilverBatteryOverview:We’llbeusingelectrochemistrytomakeabatterythatreversesthechemicalreactionthatputstarnishongrandma’sgoodsilver.Neverpolishyourtarnishedsilver‐platedsilverwareagain!Instead,setupa”silverwarecarwash”whereyouearnanickelforeverypieceyouclean.(Justdon’tletgrandmainonyourlittlesecret!)It’ssafe,simple,andjustneedshelpwiththestove.

WhattoLearn:Thisisaverysimplebatterythatworksusingelectrochemistry.

Materials

stove(withadulthelp) skillet aluminumfoil water bakingsoda salt realsilverware(notstainless)

LabTime

Youcansafelydipyoursilverwareintoaself‐polishingsolution.Here’showtodoit:

1. Lineyourskilletwithaluminumfoil.2. Addonetotwocupsofwatertoyourskillet(dependingonthesizeofyourpan.)3. Addateaspoonofsalt.4. Add1teaspoonbakingsoda.5. Whenyoursolutionbubbles,placethetarnishedsilverwaredirectlyonthefoil.Startwithasmall,really

tarnishedpiecesoyoucanseethecleaningeffectsthebest.6. Usetongstoflipitover.Thisreactionhappensquickly.7. Onlythepartstouchingthefoilwillgetcleaned,soyou’llwanttomovethefoilaround(oraddmore)soit

comesingoodcontactwiththesilver.8. Liftoutthesilverware,runundercoolwater,andwipedry.9. Tossthefoilinthetrash(orrecycling)whenyou’redone,andtheliquidsgodownthedrainwithplentyof

water.

Reading

Yoursilverturnsblackbecauseofthepresenceofsulfurinfood.Here’showthecleaningworks:Thetarnishedfork(silversulfide)combineswithsomeofthechemicalsinthewatersolutiontobreakapartintosulfur(whichgetsdepositedonthefoil)andsilver(whichgoesbackontothefork).Usingelectricity,you’vejustrelocatedthetarnishfromtheforktothefoil.Justrinsecleanandwipedry.

Thisisaverysimplebattery,believeitornot!Thefoilisthenegativecharge,thesilverwareisthepositive,andthewater‐salt‐baking‐sodasolutionistheelectrolyte.


Exercises

1. Whereistheelectrolyteinthisexperiment?

2. Wheredoestheblackstuffthatwasoriginallyonthesilverwarego?

3. Where’stheelectricityinthisexperiment?

4. WherewouldyouplaceyourDMMprobestomeasurethegeneratedvoltage?


Lesson#26:AirBatteryOverview:It’seasytousechemistrytogenerateelectricity,onceyouunderstandthebasics.Withthisexperiment,you’llusealuminumfoil,salt,air,andachemicalfromanaquariumtocreateanairbattery.We’llbeusingadigitalmultimetertofindoutjusthowmuchvoltageyourbatterycellgenerates(andthiswillalsotellyouhowmanyofthesebatteriesyouneedtomaketopoweraLEDormotor.)

WhattoLearn:This“aluminumairbattery”usesachemicalreactionbetweenthefoilandair(well,specificallytheoxygenintheair).Thecombinationofoxygenandfoilproducesaluminumoxideandenergy.Ifyoubuildyourbatterywell,youcanseetheenergywhenthisbatterylightsupanLEDorturnsamotorshaft,buttheoxidelayerwillbeinvisibletoyoureye.

Materials

salt bowlofwater activatedcharcoal(fromanaquariumsupplystore) aluminumfoil papertowel 2alligatorclipleads

LabTime

1. Fillyourbowlwithwater.2. Makeasaturatedsaltsolutionbydissolvingasmuchsaltasyoucanintothewater.Whenyoustarttosee

bitsfloatingonthebottom,you’veaddedtheperfectamount.3. Foldyourpapertowelinhalfanddipitinyoursolution.4. Layasheetofaluminumfoilonthetable.5. Pulloutthetowelandlayitontopofthefoil.6. Pouralayerofcharcoaloverthetowel,about½‐inchthick.Completelycoverthepapertowel.7. Removetheplasticinsulationfromoneofthealligatorclipleadsothemetalheadiscompletelyexposed.

(Youmayhavealreadydonethisinyourlabpreparation.)8. Laytheexposedleadinthemiddleofthecharcoalpile.9. Clipthesecondalligatorclipleadontooneendofthefoil,sothatthewireiscomingoutofotherendofthe

foil.10. Rollthepapertowelfirstaroundtheexposedalligatorlead.Youdon’twantthisleadtouchingthefoil,but

rathercompletelysurroundedbythecharcoal.Wrapitupandthenwrapthefoilarounditlikealargeburritowithonewirestickingoutofeachend.

11. Closetheendsoffsoyoudon’tleakcarbonbitseverywhere.12. ConnectthefreealligatorclipleadendstoyourDMM.


13. TurnonyourDMMto20VDC.Whatdoyouread?(Don’tforgettowrite“volts”afteryournumber!)___________________________________________________________________________________

14. Squishthebatterytomakegoodcontactbetweenthecarbon,salt,andfoil.Yourvoltageshouldchangewhenyoudothis.

15. Ifyouranswerishigherthan2.5V,thentryusingthisinplaceofyourbatterypackandattachinganLEDinasimplecircuit.

16. Ifit’slessthan2.5volts,you’llneedtoteamupwithanotherlabgroupandhookyourbatteriesuptogethertogenerateenoughpower.Here’show:a. Connectthealligatorclipleadattachedtothefoilonyourbatterytothealligatorclipleadcoming

fromthecenteroftheirbattery.b. Connectyourprobetotheirfoilalligatorwire.c. Youshouldstillhavetheotherprobeattachedtothealligatorwirecomingfromthecenterofyours.If

not,hookitup.d. Whatdoyouread?_______________________________________________________

Reading

This”aluminumairbattery”usesachemicalreactionbetweenthefoilandair(well,specificallytheoxygenintheair).Thecombinationofoxygenandfoilproducesaluminumoxideandenergy.Ifyoubuildyourbatterywell,youcanseetheenergywhenthisbatterylightsupanLEDorturnsamotorshaft,buttheoxidelayerwillbeinvisibletoyoureye.

Yourbatteryshouldlastbetween4–10minutes,dependingonhowwellyoubuildit.Youcangetalargeramountofvoltagebyusinglargerwires(withmoresurfaceareacontactingthecharcoal).Whatdoyouhavethatwouldbealargerelectrodeforthebattery?

Themoresaltyouuse,thebetteryourairbatterywillwork!You’llnoticethere’sapoint,though,wherenomatterhowmuchmoresaltyouadd,youcan’tincreasethevoltage…duetothesaturationpointofthewater.It’sbettertohaveanover‐saturatedsolution(meaningthattherearestillbitsatthebottomofthebowl).Youcanheatthewatertoincreaseitscapacitytodissolvethesalt.

Exercises

1. HowmanyairbatteriesdoesittakeforyourLEDtolightup?

2. Whichelectrodeispositive?Whichisnegative?(Hint:UsetheDMMtofigurethisout.)

3. Whatistheelectrolyteinthisexperiment?

4. Whatcouldyouuseinsteadofanexposedalligatorclipleadtomakethisbatterylastlonger?


ElectrochemistryEvaluation

StudentWorksheet

Overview:Todayyou’regoingtotaketwodifferenttests:thequizandthelabpractical.You’regoingtotakethewrittenquizfirst,andthelabpracticalattheendofthislab.Thelabpracticalisn’tapapertest–it’siswhereyougettoshowyourteacherthatyouknowhowtodosomething.

LabTest&Homework

1. Yourteacherwillcallyouupsoyoucansharehowmuchyouunderstandaboutelectrochemistryandhowitworks.Sincescienceissomuchmorethanjustreadingabookorcirclingtherightanswer,thisisanimportantpartofthetesttofindoutwhatyoureallyunderstand.

2. Whileyouarewaitingforyourturntoshowyourteacherhowmuchofthisstuffyoualreadyknow,yougettogetstartedonyourhomeworkassignment.Theassignmentisduenextweek,andhalfthecreditisforcreativityandtheotherhalfisforcontent,soreallyletyourimaginationflyasyouworkthroughit.Hereitis:Yourclassroomisgoingtobeconvertedintoaninteractivesciencemuseumnextweek.Youwillbeinchargeofoneofthestations.Youraudienceknowsnothingaboutelectricity.Yourjobistodesignandbuildanexperimentthatteachesthestudentsinlowerlevelsanimportantconceptinoneofthefollowingareas:staticelectricity,electricity,orelectrochemistry.Youwillgettoexplaintoyourstudentswhat’sgoingonasyoudemonstrateyourexperiment.Youcanhavethemwatchoractivelydosomethingatyourstation.Youwillbegradedbasedoncontentandcreativity,soreallyletyourmindgowild.(Hint:Ifyouweretheaudience,whatwouldyouwanttolearnaboutmost?)


ElectrochemistryQuiz

Name__________________________________________________________1. Namethreekindsofelectrolyteswe’veusedinourelectrochemistryexperiments.

2. WherewouldyouplaceyourDMMprobestomeasurethegeneratedvoltage?

3. Whathappensifyouusetwostripsofthesamematerial?Whatwouldhappenifweusednon‐metalstrips?

4. Whatkindsoffruitmakethebestbatteriesandwhy?

5. Whathappensifyouputoneelectrodeinonefruitandoneelectrodeinanother?

6. Wheredidthecopperonyourkeycomefrom?

7. Whatkindofbubblesformedwhenwesplitthewatermolecule?

8. Doesplainwaterconductelectricity?

9. Whydoeselectricityflowthroughsomesolutionsbutnotallofthem?

10. Whatisasalt?


ElectrochemistryLabPracticalStudentWorksheet


Materials:

AAbatterycase 2AAbatteries 2alligatorwires Disposablecup popsiclestick DigitalMultimeter

ElectrolyteOptions:

Distilledwhitevinegar Salt Sugar

Electrodeoptions:

2pennies 2nails 2pieceofplastic popsiclestick

LabPractical:

Designandbuildabatteryandshowhowmuchvoltageitproduces.

Explainfromyourexperimentabovehowchemicalenergycanbeconvertedintoelectricalenergy.


AnswerstoExercisesandQuizzes

Lesson#1:StaticHair1.Whydoesthehairsticktotheballoon?(Theballoonstealselectronsfromyourhead,makingyourheadpositivelycharged,whichisnowattractedtothenegativelychargedballoon.)2.Howdoyougetridofelectrons?(Groundtheballoonbytouchingittosomethingmetal.)3.Canyouseeelectrons?Whyorwhynot?(No–theyaretoosmall!)4.Doesitmatterwhatkindofhairyourubtheballoonon?(Yes–finehairwithoutanyhairproductsaddedworksbest.)5.Howlongdoesthehaircontinuetostandupafteryouremovetheballoon?(Anywherebetween2secondsand2minutes.)6.Doesitmatterwhatkindofballoonyouuse?(Yesandno.Yes:materialthattheballoonismadeoutof,andthicknessoftherubber.No,theshapedoesnotmatter.)7.Howfastorslowdoyouneedtorubforthebiggestchargeontheballoon?(Fast,asinvigorously.)8.Doeshaircolormatter?(No.Thetextureofthehair,howfinethehairis,andwhetheryou’vegoopeditupornotwillaffectthisexperiment.)Lesson#2:ElectricFields1.Whydidthepingpongballmove?(Thepingpongballhasnochargeonit,meaningithasanequal,balancednumberofelectronsandprotons.Theballoonhasalargenegativechargeonit,sowhenyoubringitclosetothepingpongball,theelectronsintheballoonrepeltheelectronsintheballoon,leavingthepositiveprotonsexposedtotheballoon.Thosepingpongballprotonsareattractedtotheballoon’selectronssotheballrollstowardtheballoon.)2.Whydidthepaperjumpup?(Theballoonhasalargenegativecharge.Thepaperhasanequalbalanceofnegativeandpositivecharges,soit’scurrentlyneutral.Theelectronsinthepaperarequicklyrepelledbytheelectronsintheballoon,leavingthepositiveprotonstobeattractedtothenegativeelectronsintheballoon.)3.Doesthepapersticktotheballoonforever?Whyorwhynot?(Nope.Thepaperbitsbegintostealelectronsfromtheballoonwhentheygetstucktoit,makingthepapernegativeallover.Sincenegativechargesrepeleachother,thepaperjumpsofftheballoon.)4.Whatmadethewatermove?(Thewatermoleculeisapolarmolecule,meaningthatitactslikeatinybarmagnetinthatithasapositiveandnegativeend.Waterisaliquid,whichmeansthattheselittlewatermoleculescanrotateandmoveeasily.Thechargedballooninfluencesthedirectionthatthemini‐magnetslineupastheyflowpast.)5.Doesitmatterifthewaterishotorcold?(Nope,notreally.)6.Whatotherliquidsdoyouthinkwouldworkbesideswater?(Anywater‐basedliquidwillwork,likevinegar,juice,etc.)7.Doesitworkwithafullstreamofrushingwater?Apanfullofwater?Whyorwhynot?(Asmall,thin,steadystreamworksbestbecausetheballoonneedstoinfluencethemolecules.Iftoomanyarerushingpast,theballoonneedstohaveastrongerchargetoinfluenceit.)8.Whichway(attractedorrepelled)didthesoapbubblemove?(Attracted.)9.Whatholdsthepackingpeanuttothewall?(Thechargedpackingpeanut’snegativechargeiscausedbyhavingtoomanyelectrons.Whenyoustickthefoampeanutonthewall,theelectronsinthefoamrepeltheelectronsinthewall,leavingthepositiveprotonsexposed,butthoseprotonsdon’tcareatall,becausetheyareattractedtothenegativeelectrons,andthisattractiveforcekeepsthefoamstuckinplace.)


10.Dotheseexperimentsworkifit’sraining?Whyorwhynot?(No–humidityisextrawatermoleculesintheair,andthesewatermoleculesallowelectronsthatarepilinguptobleedoffintotheair,preventingachargefrombuildingup.)11.Whatifyougettheballoonwetfirstandthentrytheseexperimentsagain?(Seeanswer#10)12.Doesthepapersticktotheballoonlongerthanthepackingpeanutssticktothewall?(No,becausethepapertakesonthenegativeelectricchargeandisquicklyrepelledbythenegativechargeintheballoon,whereasthewallandthepackingpeanutsarehappilyattractedtoeachother.)Lesson#3:TriboelectricSeries1.Whathappenedtothestripofplasticafteryouranitthroughyourfingers?(Theplasticisattractedtoyourhandandmovesnotonlytowardyourhand,butyourarmandclothes!)2.Isthestripattractedtoneutralobjects?Whyorwhynot?(Yes.Thestripmovestowarddesks,chairs,andthewall.Theplastichasahugenegativechargeonit.Whentheplasticgetsclosetothedesk,thenegativechargesrepeltheelectronsontheobject,leavingthesurfaceneartheplasticpositivelychargedandattractedtotheplastic.)3.Whathappensifyouchargetwoplasticstrips–aretheyattractedorrepelledfromeachother?(Repelledbecausetheybothhavethesamenegativecharge.)4.Howlongdidyoukeepthebagfloatingabovetheballoon?(Timevaries.)5.Whydidtheplasticbagpiecefloatabovetheballoon?(Theyarebothchargedwithahugenegativecharge.)6.Whatwasthedifferencewhenyourubbedthefoamplatewithwoolversuswithabag?(Whenyourubthefoamplatewiththewool,theplatetakesonelectronsandcreatesanegativechargeontheplate.Togivetheplateapositivecharge,rubitwithaplasticbag.)7.Whichcombinationgavethebestresultsforkeepingyourglideraloft?(Answervaries–askthekidsfortheirbesttestresultsafterthey’vefinishedtheirexperimentsandrecordthemforeveryonetosee.)Lesson#4:VisibleElectricFields1.Whathappenedwhenyoubroughtachargedballoonnearthedill?(Thenegativechargesinthedillareattractedtotheballoonandthepositivechargesarerepelled,sothedilllinesuptoindicatethefielddirection.)2.Whatsideofthedillwasattractedtotheballoon?(Positive)3.Whathappenedwhenyoubroughttwonegativechargesnearthedill?(Thedillwillmovelessthanifyouhadplacedapositiveandnegativechargeatthewires/aluminumfoil.)4.Wereyouabletomakethedillcomeoutoftheliquidandontotheballoonwithouttouchingtheoil?(Ifyoumovetheballoonjustright,theattractiveelectricalchargewillpullthelightweightdillrightupoutoftheoilandontotheballoon.)Lesson#5:Electroscope1.Whydothefoilstripsspreadapart?(Likerepelslike.Thechargefromtheballoonispickedupbythefoilball,whichconductsittodownthepaperclipandtothefoilleaves.Thefoilspreadsapartbecausetheyarebothnegativelycharged.)2.Howdoyoudischargetheelectroscope?(Touchitwithyourhandstobalancetheplusandminuscharges.)3.Whydidweuseaglassjar?(Glassisagreatinsulatoragainstwindcurrentsandnotaseasytotipoverasaplasticbottle.)4.Doestheelectroscopereactthesamewaywhetherit’sexposedtoapositiveornegativecharge?(Yes–itdetectsbothequallywell.)5.Listfourwaystochargetheelectroscope.(Balloon‐hair,wool‐PVCpipe,twofoamplatesrubbedtogether,plasticbaggieandfoamplate.)


Lesson#6:ElectrostaticMotor1.Whathappensifyourubtheballoononotherthings,likeawoolsweater?(Yougetapositivechargeontheballoon,whichdoesn’taffecttheexperiment.Theballoonwillstillmaketheyardstickmovewhetherit’spositivelyornegativelycharged.)2.Ifyoupositionotherpeoplewithchargedballoonsaroundthetable,canyoukeeptheyardstickgoing?(Yes.)3.Canweseeelectrons?(Nope.Theradiusofanelectronisapproximately0.000000000000002meters)4.Howdoyougetridofextraelectrons?(Groundyourselfortheobjectbytouchingsomethinglikethefloororawaterpipethat’sburiedintotheearth.)5.Whydoyouthinktheyardstickmoved?(Thenegativechargeintheballoonrepelstheelectronsintheyardstick,exposingthosepositiveprotons,whichareattractedtotheballoon.Sincethestickisfreetorotate,itchasestheballoonaroundinacircle.)6.Whatwouldhappenifyouusebothapositivelychargedobjectandanegativelychargedobjecttomaketheyardstickmove?(Nothing–thechargesintheyardstickgetconfusedanditstaysput.Or,ifyou’rereallycarefulaboutwhereyouplaceeachone,youcouldpossiblygetittomoveabit.)Lesson#7:AdvancedStaticLab1.Whatiscommonthroughoutalltheseexperimentsthatmakethemwork?(Oppositechargesattract,likechargesrepel.)2.Whatmakestheneonbulblightup?Whatelsewouldworkbesidesaneonbulb?(Neonbulbslightupbecausetheelectricalfieldexcitesthegas,whichthengivesoffapinkish‐orangelight.Afluorescenttubeislinedwithwhitestuffcalledphosphor,whichgivesofflightwheneverit’sstruckbyUVrays.ThetubeisfilledwithagasthatgivesoffUVrayswhenplacedinanelectricalfield.Whenthebulbisbroughtclosetoastaticcharge,electronsripthroughthetubeandgoouttheotherside.Astheygothrough,theysmackintothegasvaporwhichreleaseslightrays(UVinafluorescenttube)thathitthephosphorontheinsideofthetube,whichthenemitslight.Fluorescentlights,oranytubeofgasfromthenoblegasescolumnontheperiodictable…likeneonwillalsoglowinanelectrically‐chargedfield.)3.Doesitmatterhowfarapartthesoupcansare?(Yes–iftheyaretoofarapart,theballisn’tattractedtotheoppositecan.)4.Whydoesthefoilballgobackandforthbetweenthetwocans?(Theballtakesonthechargeofthenegativelychargedcan(chargedbytheFlyStick),andisthenrepelledsincetheyareboththesamecharge.Itswingstotheoppositecanwherethechargebalanceisrestored.Thenthepositiveprotonsseethenegatively‐chargedsoupcanandareattractedtoitandthecyclestartsallover.)5.WhydothepanstakeonthesamechargeastheFlyStick?(Aluminumconductselectricity.)6.Whenstickingasheetofpapertothewall,doesitmatterhowlongyouchargethepaperfor?(Yes,butonlyuptoapoint.Seeresultsfromtabletodeterminewherethispointis.)7.Drawadiagramtoexplainhowtheelectrostaticmotorworks.Labeleachpartandshowwherethechargesareandhowtheymaketherotorturn.

a.TheFlyStickchargesoneofthestatorswithabignegativecharge,whichisverydifferentfromtheground(balance)chargeoftheoppositestator.Thechargeisconductedthroughthepaperclipandontothefoilarea,whichpicksupthesamechargeasthepaperclip.Likechargesrepel,sotherotorstartstoturn,bringinganewfoilareaunderthepapercliphook.Tinysparksjumptothenewareasandchargethem,whichmakethemattract/repelfromthestatorsanditcontinuestoturn.Thefoilontherotorunderthepapercliphookisalwayschargedwiththesamechargeasthepaperclip,soit’sbeingrepelledorattractedsideways.Ifyouputapositivechargeinsteadofgroundingit,therotorwillspinevenfaster.


b.Youcanalsothinkoftherotorlikeawaterwheel.Imagineturningthewholethingsidewaysandononeside,thenegativechargeispouringintothesideoftherotorthatisfallingtowardthegroundingfilmcan.

Lesson#8:AlienDetector1.WhentheLEDison,whatdoyouthinkitmeans?(Itdetectsapositivechargeregion.)2.DoestheLEDturningoffdetectanything?(Yes–anegativechargeregion.)3.Doalienslikehumidity?(No–thisexperimentdoesn’tworkinhighhumidity.)4.Howdoesthisaliendetectorreallywork?(It’sapositivechargestaticdetector…thisisimportant,becausenowyouknowwhentheLEDisoff,thespaceyou’redetectingisnegativelycharged,andwhenit’slitup,you’reinapocketofpositively‐chargedparticles.)Lesson#9:CosmicRayDetector1.Howdoesthisdetectorwork?(Whentheparticleentersthechamber,itsmacksintothealcoholvaporandmakesfreeions.Thevaporinthechambercondensesaroundtheseions,forminglittledropletswhichformthecloudtrail.)2.Doallparticlesleavethesametrail?(No.Differenttypesofparticlesleavedifferenttrails.Alphaparticlesareheavyandcreatestraight,thicktrails.Betaparticles,whicharelight,willleavelight,wispy,trails.Ifyouseeanycurlytrailsorstraightpathsthattakeasharpturn,thoseareparticlesthathavesmackedintoeachother.)3.Whathappenswhenthemagnetisbroughtclosetothejar?(Youcanuseamagnettodeflectthecosmicraysifthemagnetisstrongenoughandpositionedjustright.)Lesson#10:BasicCircuits1.WhatdoesLEDstandsfor?(“LightEmittingDiode.”)2.DoesitmatterwhichwayyouwireanLEDinacircuit?(Yes,LEDsarepolarized.)3.DoesthelongerwireontheLEDconnecttoplus(red)orminus(black)?(Longerleadispositive,andtheflatsideonthelensisnegative.)4.Doyouneedtohookupbatteriestomakeaneonbulblightup?Whyorwhynot?(No.Theneonbulb(fromLesson#7willlightupfromstaticelectricity.Nobatteriesrequired.Theneonlamprequiresverylittleamps,buthighvoltagetoilluminate,whichyoucangetbychargingyourselfup.Simplyholdoneleadandscuffalongthecarpetandtouchtheotherleadtoyourcat'snose.Orholdoneleadandslidedownanon‐metalslide.)5.What'sthedifferencebetweenalightbulbandyourLED?6.Whatisthedifferencebetweenaboltoflightningandtheelectricityinyourcircuit?(Oneone:quantity.)7.Whatisthechargeofanelectron?(Negative)Lesson#11:ConductivityTesters1.Namesixmaterialsthatareelectricallyconductive.(Sodacans,quarters,paperclips,braces,unpaintedeyeglasses,andyourtongue.)2.Whatkindsofmaterialsareconductorsandinsulators?(Materialswithfreeelectrons,likemetals,areconductors.Insulatorsarelikepaper,ceramics,andrubber.)3.Canyouconvertaninsulatorintoaconductor?How?(Yes,that’swhatasemiconductoris.It’slikeaswitchinablackbox.Sometimesitconductsandsometimesitdoesn’t.Ifit’sadimmerswitch,thenitconductstodifferentdegreesdependingonthepositionofthedimmer.)4.Namefourinstanceswheninsulatorsareabadideatohavearound.(Whenyouneedtoconductelectricity,liketoabulb,motor,relay,buzzer,etc.Alsowhenstaticchargecanharmacircuit,youneedawaytodischargeregularlytoavoidbuild‐up.)5.Whenareinsulatorsessentialtohave?(Whenyouwanttoturnoffalight.)


Lesson#12:Switches&Motors1.Ifyouwanttoreversethespindirectionofamotorwithoutusingaswitch,whatcanyoudo?(Switchthewiresonthebackofthemotor.)2.Asimpleswitchcanbemadeoutofwhatkindsofmaterials?(Youneedtobeabletocontrolwhenitconductsandinsulates.Takethetwowires(onefromthebatteryandtheotherfromthemotor)andtouchthemtogether–ON–OFF–ON–OFF.Simplestswitchintheworld!Airistheinsulatorandmetalistheconductor.Butyoucanalsouseindexcards,paperclips,andbrassfasteners.)3.HowwouldyoumakeyourSPSTswitchanNC(normallyclosed)switch?(Leavethepaperclipinitsnormalshape(don’tbendintoaV)andtouchthepapercliptothebrassfastener.Themotorwillrununtilyoumovethepaperclipaway.)4.HowdidyouhavetoconnectyourcircuitinorderforboththeLEDandmotortoworkatthesametime?(Iftheywireitupinseries(plustominus),they’llfinditdoesn’twork.Iftheyhookitupinparallel(plustoplus),thenbothwillworkwithonebatterypack.)5.DrawapictureofyourexperimentthatexplainshowtheSPSTswitchworks,andshowhowelectricityflowsthroughyourcircuit.ExtraCredit(forstudentswhohavecompletedPart3):6.DrawapictureofyourexperimentthatexplainshowtheDPDTswitchworksinyourcircuitandshowhowtowireupthecircuit.Lesson#13:DigitalMultimeters1.Ifyoumeasure2.65voltsfromyourbatterypack,doyouneednewbatteriesorwilltheywork?(Youhavetotesteachbatteryindividuallytoseeiftheyarebothabove1.3volts.)2.HowdoyouthinkyouwouldmeasuretheresistanceofanLED?(Turnthedialtothe“Ω”marktomeasureohmsandputeachoftheprobesononeoftheLED’swiresandreadthevalue.)3.Resetyourmeterforaquickpracticaltest:RemovethewiresfromyourDMMandsetthedialatOFF.Waveyourhandwildlyandshowyourteacherhowyoucanusethemeter(youcanaddprobesandturnitonnow)totestthevoltageonyourLEDinasimplecircuitdoingthestepsfromtheexperiment.Lesson#14:MotorSpeedControllers1.Howdoesapotentiometerwork?(Apotentiometerisaresistorwiththreeterminalsthathasaslidingcontacttovarytheresistance.Resistanceisameasureofhoweasilycurrentflowsthroughawire.Themoretheresistance,thelesscurrentflowsthroughthecircuit.We’regoingtouseoursasavariableresistor.)2.DoesthepotentiometerworkdifferentlyontheLEDandthemotor?(No,buttherangemaydiffersincethemotordrawsmuchmorecurrentthantheLED.)3.Namethreeplacesyou’veusedpotentiometersineverydaylife.(Potentiometersareeverywhere:volumecontrols,dimmerswitches,radiodials.)4.HowdoyouthinkyoumightwireupanLED,switch,andpotentiometer?(Theyareallinserieswitheachother.)Lesson#15:ElectricEyeSensor1.HowisaCdScelllikeaswitch?Howisitnotlikeaswitch?(Theflowofcurrentiscontrolledbytheamountoflightthatfallsonthedetector.It’sunlikeaswitchinthatitneverreallystopsthecurrentcompletely.)2.WhenistheLEDthebrightest?(Infullsun.)3.Howcouldyouusethisasaburglaralarm?


Lesson#16:TripWireBurglarAlarm1.Howdoesthiswork?(TheLEDlightsupasyou”push”(squeeze,really)theswitchbyopeningtheclothespin.We’vereversedthissotheLEDisalsodarkuntilyouyankthepaperaway.Toarmthetripwire,insertasmallscrapofpaperbetweenthetacks.Thisworksbecausepaperdoesnotconductelectricity.Whenthepapergetsyankedout,thetackstouchand…GOTCHA!!!)2.Whattypeofswitchisthetripwire?(ThetripwireisanNC[normallyclosed]switch.)3.Namethreeplacesyoucaninstallthisalarm.(Acrossthebottomofadoorway,insideadrawer,orattachedtoacupboarddoor.)Lesson#17:PressureSensor1.Howdoesthissensorwork?(Whenyousqueezeit,you’regettingthetwofoilsquarestotouchthroughthehole,whichallowscurrenttoflowtoyourLED.Whenyoureleaseit,thefoilspreadsapartagainbecausetheyareonoppositesidesofthefoamsquare,whichinsulatesandinterruptstheflowofelectricity,andtheLEDgoesdark.)2.WhatmakesthisanNOswitch?(Anormallyopenswitchdoesn’tallowcurrenttoflowwhenit’ssittingtherebyitself.Whenyouactivateit(inourcase,steppingonit),thenitallowselectricitytoflow.)3.Howcanyouuseboththetripwireandthepressuresensorinthesamecircuit?Drawitouthere:Lesson#18:LatchingCircuits1.Whatisarelay?(Arelayisaswitchyoucanturnonandoffusingelectricity.)2.Whatdoestherelaydointhiscircuit?(TherelaykeepstheelectricityflowingtotheLEDafterthepressuresensorshutsitoff.TheSPSTswitchresetstherelay.)3.Drawoutapicturethatshowshoweverythingisconnectedinyourcircuit:Lesson#19:NerveTester1.Canyoutraveltheentirepathwithoutturningonthelight?(Answersvary)2.Whereinyourcircuitcanyouaddaswitchtoturnthegameonandoff?(Answersvary)Lesson#20:Electrolytes1.Whydoeselectricityflowthroughsomesolutionsbutnotallofthem?(Saltmixeswithwaterandseparateintopositively(Na+)andnegatively(Cl‐)chargedparticles(ions).Ifyoupassacurrentthroughthesolutionofsaltandwater,oppositesattract:thepositiveionsareattractedtothenegativepoleandthenegativeionsgotowardthepositivepole.Thesemigrationsionsallowelectricitytoflow,whichiswhysaltsolutionsconductelectricity.)2.Whatisasalt?(Whenasubstancemixeswithwaterandseparatesintoitspositiveandnegativeparts,it’scalleda“salt.”)3.Howareelectrolytesusedtodayinreallife?(Oneexample:thebodyuseselectrolytessuchassodium,calcium,potassium,chloride,magnesium,andmoretoregulatethenerveandmusclefunction,keepyourbodyhydrated,andmaintaintherightpHintheblood.)4.Whichsubstancewasyourtopconductor?(Checkdataforresult.)5.Whichsubstancedidn’tconductanythingatall?(Checkdataforresult.)6.Whathappensifyoumixanelectrolyteandnon‐electrolytetogether?(Checkdataforresult.)Lesson#21:Electrolysis1.Whyarebubblesforming?(Bubblesformasthegasesareproduced.Asthewatermoleculebreaksapartintosmallerpieces:hydrogenions[positivelychargedhydrogen]andoxygenions[negativelychargedoxygen],theybubbleupintothetesttube.)


2.Didbubblesformatbothwiresoronlyone?Whatkindofbubblesarethey?(Hydrogenbubblesformedatoneofthewiresandoxygenformedattheother.)3.Whatwouldhappenifyoudidthisexperimentwithplainwater?Woulditwork?Whyorwhynot?(Youneedtheelectrolytestocarrythecurrentthroughthewaterandseparatethewatermoleculeintoitsions.Withoutit,thewateractslikeaweakinsulatorandnobubbleswillform.)4.Whichterminal(positiveornegative)producedthehydrogengas?(Thepositivehydrogenionszipovertothenegativeterminalandformtinybubblesrightonthewire.)5.Didthereactioncreatemorehydrogenormoreoxygen?(Sincewateristwohydrogenatomsandoneoxygenatom,thisexperimentgeneratestwiceasmuchhydrogenasoxygen.)Lesson#22:Electroplating1.Lookatyourkey.Whatcolorisit?(Blackuntilyouwipeitoff,thencopperordullbrownunderneath.)2.Wheredidthecopperonyourkeycomefrom?(Thecopperionsinthesolution.)3.Whathappenedwhenyouaddedasecondbattery?(Thereactionhappensmuchfaster.)4.Whichcircuit(seriesorparallel)didthereactionacceleratefasterwith?(Checkdataresults.)Lesson#23:FruitBattery1.Whatkindsoffruitmakethebestbatteries?(Citrus,becauseoftheacid.)2.Whathappensifyouputoneelectrodeinonefruitandoneelectrodeinanother?(Theionsarenotabletobeattractedtothedifferentelectrodes,sothere’snocurrentflowing.)3.Whathappensifyoustickmultipleelectrodepairsaroundapieceoffruit,andconnecttheminseries(zinctocoppertozinctocoppertozinc…etc.)andmeasurethevoltageatthestartandendelectrodes?(You’llgetahighvoltageatfirst,whichrunsoutmorequicklythanusingonlyasinglepair.)Lesson#24:SaltyBattery1.Whichcombinationgivesthehighestvoltage?(Checkdataforresult.)2.Whathappensifyouusetwostripsofthesamematerial?(Youwon’thaveadifference.Thesecopperionsinteractwiththezincelectrodetoformzincions.Thecopperelectronsarechemicallyreactingwiththelemonjuicetoformcopperions.Thedifferenceinelectricalcharge(potential)onthesetwoplatescausesavoltage.)3.Whatwouldhappenifweusednon‐metalstrips?(Theydon’tbreakintoions,anddon’twork.)Lesson#25:SilverBattery1.Whereistheelectrolyteinthisexperiment?(Thewater+salt+bakingsodasolution.)2.Wheredoestheblackstuffthatwasoriginallyonthesilverwarego?(Onthefoil.)3.Where’stheelectricityinthisexperiment?(Thesolutionisheated,addingtheneededenergymakethischemicalreactiontakeplace.Thecurrentflowsfromplus(silverware)tominus(foil).)4.WherewouldyouplaceyourDMMprobestomeasurethegeneratedvoltage?(Theblackprobeonthefoilandtheredprobeonthesilverware.)Lesson#26:AirBattery1.HowmanyairbatteriesdoesittakeforyourLEDtolightup?(Checkdataresults.)2.Whichelectrodeispositive?Whichisnegative?3.Whatistheelectrolyteinthisexperiment?(Saltwater.)4.Whatcouldyouuseinsteadofanexposedalligatorclipleadtomakethisbatterylastlonger?(Zinc,copper…etc.)


VocabularyfortheUnit

Ifanatomhasmoreelectronsspinninginonedirectionthanintheother,thatatomhasamagneticfield.Atomsaremadeofacoregroupofneutronsandprotons,withanelectroncloudcirclingthenucleus.

Theprotonhasapositivecharge,theneutronhasnocharge(neutron,neutralgetit?)andtheelectronhasanegativecharge.Thesechargesrepelandattractoneanotherkindoflikemagnetsrepelorattract.Likechargesrepel(pushaway)oneanotherandunlikechargesattractoneanother.Generallythingsareneutrallycharged.Theyaren’tverypositiveornegative,butratherhaveabalanceofboth.

Whenelectriccurrentpassesthroughamaterial,itdoesitbyelectricalconduction.Therearedifferentkindsofconduction,suchasmetallicconduction,whereelectronsflowthroughaconductor(likemetal)andelectrolysis,wherechargedatoms(calledions)flowthroughliquids.Metalsareconductorsnotbecauseelectricitypassesthroughthem,butbecausetheycontainelectronsthatcanmove.

LEDstandsfor“LightEmittingDiode."Adiodeislikeaone‐wayvalveforelectricity.Itletscurrentgothroughitoneway,butnottheother.Theyhavetwoleads,calledtheanodeandthecathode.

Electricityisaflowofelectrons.Aflowofelectronscreatesamagneticfield.Magneticfieldscancauseaflowofelectrons.Magneticfieldscancauseelectricity.

Electronscanhavea“left”or“right”spininadditionto“goingaround”thenucleus.Electronstechnicallydon’torbitthecoreofanatom.Theypopinandpopoutofexistence.Electronsdotendtostayatacertaindistancefromanucleus.Thisareathattheelectrontendstostayiniscalledashell.Theelectronsmovesofastaroundtheshellthattheshellformsaballoon‐likeballaroundthenucleus.

Afieldisanareaaroundanelectrical,magneticorgravitationalsourcethatwillcreateaforceonanotherelectrical,magneticorgravitationalsourcethatcomeswithinthereachofthefield.Infields,theclosersomethinggetstothesourceofthefield,thestrongertheforceofthefieldgets.Thisiscalledtheinversesquarelaw.

Objectsthatareelectricallychargedcancreateatemporarychargeonanotherobject.

Aschematicisasimpleline‐drawingofanelectricalcircuit.

Atransistoriskindoflikeanelectronicdimmerswitch.Thinkofalightdimmer–youknow,thekindthatyoumighthaveonthelightsinaroominyourhouse,orafriend’shouse.Youturnaknoborslidealever,andallthelightsdim.

Thetriboelectricseriesisalistthatranksdifferentmaterialsaccordingtohowtheyloseorgainelectrons.

LECT RICITY - Supercharged Science | Supercharged Science€¦ · Static Electricity Lab Practical...

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Transcript of LECT RICITY - Supercharged Science | Supercharged Science€¦ · Static Electricity Lab Practical...