Electron2Electricity-obooko-hist0017

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http://www.obooko.com/


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A Journey From

Electron To Electricity

History Should Never be a Mystery.............


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CCOONNTTEENNTTSS Introduction

Story describing the importance of history -6

The beginning of electrical history -11

Father of electricity & magnetism -12

How magnetic compass works? -16

Birth of first Electrical Generator -17 Electroluminescence -22

Early Electric Machines -23

First experiment to transmit Electric Power

over a long distance -27 Leyden J ar, the first storage device -33

Benjamin Franklin & Kite Experiment -37

What is the speed of electricity? -42

The life of Henry Cavendish -44

Electroscopes & Electrometers ( The earlyvoltmeters) -45

Charles-Augustin de Coulomb -48

Story of Invention of Waterwheel -50

Brief History of the Steam Engine -59


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Birth of Bioelectricity -65

Invention of Voltaic Pile (Battery) -68

Dream still remained as a Dream -73 An Observation That Has Changed The World -

75

The Foundations For Electrodynamics -77

A history of the evolution of electric clocks -80

Electric eel -82

History of Electrochemistry -83

Invention of the first electric arc lamp -87

History of the Incandescent light bulb -93 Development of the Electromagnet -99

The man who laid foundation for Modern world-102

History of Electric Generator -108

History of Electric Motor -120

History of Transformer -130

History of wind power -138

The Story of Electrical and MagneticMeasurements -145


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History of Electric Locomotive -150

Thomas Alva Edison -154

Why 50Hz power supply is standard in allcountries? -158

Nikola Tesla, The Life & Times Of ForgottenGenius -159

The War of Currents -164


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In this book the required information is collected from manywebsites, books, articles, newspapers & some documentaryvideos. In some cases only one word or one sentence or oneimage is taken from a particular website/book. So consideringspace & some other factors we are unable to provide all thereferences but only sources from where maximum informationcollected is mentioned. We apologize for using information fromany website/book & not mentioning. The major source of information is from Wikipedia & Spark Museum. At initial stages we were unable to find required information & also wewere not clear about the topics to be included at that time thesetwo sources provided a proper path for us. So we are glad for anopportunity to thank them for their direct or indirect help.

A special Thanks to

GiriBabu K [email protected]

http://journeytomysteriouslife.wordpress.com/


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Letter to Spark Museum

Respected Sir,M y name is Giri Babu K E and I am currently pursing my Bachelor's in ElectricalEngineering from Sri Jayachamarajendra Co llege of Engineering in M ysore,Karnataka India. Being a student of Electrical Engineering, I was felt the urge tocontribute something towards the development of my branch. In this regard,Some of my friends and myself, have collated a book called " H istory OfElectricity" to serve the purpose, the major intent being to arouse interest in thestudents towards electricity and m ake education as lively as possible.T he information in the book is collected from different websites across theinternet, some books and documentaries. Among these, the major source ofinformation is your website. When we first started the project we did not knowhow to go about w ith it. We were totally confused about the topics to beincluded, at this juncture, your help proved to be crucial for us. So we are veryglad to take this opportunity to thank you for the support and a lso request you topermit us to utilize the information present in your website.A t the present moment, we are still undecided about approaching any publisherfor the book. Our m ain aim still remains to make an effort to spread the book toeveryone who needs it. We have worked more than three years on the book,collecting information from various sources, and arranging information in asuitable format hoping to create eagerness in our fellow students.

W e are also sending one copy to you , if there are any mistakes, or additions tobe made on our behalf, please intimate us. We would be glad to hear from youSir.Thanking you in advanceyours faithfullyGiri Babu K E


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Letter from Spark Museum

Hello Giri,You are welcome to use my site as a source for your PDF (very nice job, by theway). Before I can grant publishing rights in any other form I would need toknow more specifics, so please do let me know if you plan to publish in print.Best regards,John Jenkinswww.sparkmuseum.com


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INTRODUCTIONA n enormous part of our lives is affected by electricity, from dawnto dusk, from the geyser which we turn ON on the morning wake, the power toour coffeemaker, the traffic lights on our way to workplace, and the computersand equipment we use once we get to place. Without electricity, life, as we know,would be dramatically different. Still, most of the people never stop to thinkabout how this essential utility became such a huge part of our lives.There requires no deep research in the pages of antiquity to trace

the rise & progress of the science of electricity. Electricity existed as lightning in theskies since the beginning of the universe, even before there was life on earth.Early-times our ancestors, those who were residing in caves, probably recognizedthe force of electricity when lightning struck. There are evidences that, we wereaware of electricity as far back as 600 BC. Thales of M iletus is thought to be, thefirst to study the creation of electrical energy. While experimenting with amberrods, Thales found that, after rubbing them, they attracted lightweight objects. Butit sprang into being in comparatively recent times; & after the first halting-stagesof its existence were surmounted, it advanced from infancy to manhood with therapidity of its own lightning spark; it has attained a degree of importance scarcelyto be equalled by any of the physical sciences.T here are many great names, great souls who contributed for thedevelopment of this field. The pain, tears, stress they have experienced physically,mentally, emotionally in the development of this field is something which isimmortalized in the annals of Electrical history. But even then, in this 21 st centurywith technology at the tip of fingers why are we still failing in the properutilization of natural energy? Why even today almost half of the power generatedis lost before it is utilized by a consumer? Why electrical field is still lagging in R &D field compared to other, why in electrical we talk much about evolution ratherthan revolution. Why many villages are still not electrified? Can you believeaccording to R.E.B (Rural Electricity Board) & S.E.B (State Electricity Board) stillaround 80,000 villages are yet to be electrified in India (according to 2004 senses).Sounds unbelievable but sti ll there are people who have not seen a glowing bulbin their entire life. Electricity-one of the sciences most wonderful blessings is stillout of their reach. Why have we failed to m ake ourselves electricity-self sufficientthough we are blessed with the most resourceful nature?


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We are confident that the topics we have discussed in this book wouldbe of intellectual interest to you. W e do not claim any credits for this The creditgoes to the topics themselves. Let we stop this preamble here , may we now inviteyou dear reader for a journey from electron to electricity, please do bear in mindthat we are only a tourist guide & fellow-travellers .

B efore will get into the discussion, I know what all might bethinking why should we know about history? What so important about it? Afterall, it has already happened. There is nothing we can do to change it. What is thebig deal? In fact, a vital part of a successful future depends on knowing about thesuccesses and failures of the past. If you are not agree, let me tell you a story tomake the disagree; agree.T he following story describes how im portant it is to know the history.Source: Documentary on Archimedes by PBS-NOVA titledInfinite Secrets-The Genius of Archimedes

This is the book that could have changed the history of the world,it contains the revolutionary ideas of a gen ius who was centuries ahead of h is timeArchimedes. The book was lost to the world for more than thousand years,passing through the hands of scribes, monks, forgers. Yet no one seems to knowthe books true value until it surfaced at auction selling for 2 million dollars. Thebuyer who was a billionaire instead of hiding it away he put the manuscript intothe hands of those who could unlock i t secrets.


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B ut interpreting Archimedes manuscript proved tobe more difficult than any one had imagined, thenewly invisible tracings of his words lay under thewritings of prayer book. As scientists worked torecover the text from this fragile document theydiscovered that the Archimedes was further aheadof his time than they had ever believed, if hissecrets were not hidden for so long the worldtoday could be a very different place. We couldhave been on Mars today; we could haveaccomplished all of the things people are predictingfor centuries from now.This book is nothing but Archimedes brain & it for us to dig intothat & pull out new thought & what he has to say in the combination ofremarkable journey one that began 2000 years ago.


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A typical page from the Archimedes Palimpsest. The text of the prayer book isseen from top to bottom, the original Archimedes manuscript is seen as faintertext below it running from left to right.


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As soon as you heard Archimedes name you will remember the story of crown, ifyou havent here is the story for you. O n one particular day Archimedes wastrying to solve about a problem of golden crown given to the king of Syracuse,the king suspected that the jeweller had cheated him and substituted some lessprecious metal for the gold. King asked Archimedes to find a way to demonstratethat the crown was not pure gold without melting it.A rchimedes struggled with the problem for a very long time. Then,one day, as he stepped into a bathtub filled with water, he saw that the wateroverflowed. He noticed that the amount of water that overflowed the tub wasproportional to the amount of his body that was submerged. & this would app lyto the crown too, he could find density of the crown by immersing it in a vessel ofwater & seeing how much water is displaced. He is so excited by this discoverythat he immediately leaped out of his bath & without throwing any clothes on heran naked through the streets shouting the Greek word Eureka means I found it.W hat he had discovered was the principle of liquid displacement &a way to prove the kings crown was too big to be a pure gold.A rchimedes not only excels in mathematics but he was an inventoras well, many of h is ideas were used in machines today, but he was best known &feared for his weapons of war. But Archimedes true love was mathematics; hedevised an ingenious method using straight lines to measure a circle finding thevalue of . Its one of the most widely used mathematical values today;Archimedes wants to find a value as close as possible to the ratio of circumferenceof a circle to its diameter.D iscovering the value of

w e come across many formulas in our daily life but none of us know themeaning & true value of it. Let me give you an example, suppose if I tell you to


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calculate area of a circle with radius 5 cm. you just take calculator press multiply by 5^2 & press = the result is 78.53 sq.cm. How much time youneeded to solve this? Assuming you had calculator in your hand it will not takemore than 5 seconds. What if I tell you that it actually takes 5 days, you willlaugh at me. But it actually does if you had not appreciated the value of . Likeeveryone else I was also not knowing the meaning of it until I read aboutArchimedes.In 2000 years ago they didnt had any instrument/ technique to find

the area of a circle. They could be ab le to find area of geometry with only straightlines. This was the puzzle for many in those days. Then Archimedes venture tofind a solution for the same with the help of po lygons.What he did was, He began with a circle & then inscribed a triangle in it like ashell, he could find the perimeter of triangle since it has straight sides & now theperimeter of triangle is less than the perimeter of the circle. This represented firstapproximation a lower bound to the circumference of a circle.Continuing further he inscribed the pentagon then hexagon & determining itscircumference he had better approximation. He continued this way going from6,12,24,48 & finally ended with 96 & he didnt stopped their he repeated thesame for the outside the perimeter of a circle. The circumference lies between theperimeter of outer & inner polygons which can be measured because they havestraight sides. Like this he took the circles with different sizes & repeated the sameprocedure. By examining the results closely he could sense something commonamong them. Then he tried to fit the diameter around the circumference of acircle, to his surprise he found that how big/small the size of circle the diameterwill fit around the circle 3.14 time s a very good approximation for what we nowcall . With this he can find the area of any circular object by a simple formulaA=r^2. A rchimedes death in 212 B.C. brought golden age in Greekmathematics to an end. There was no one who could follow him. The Greekmathematicians slowly declined & then the Dark Age, the ages were all interest inmathematics was lost & as a result nothing really interested there scientifically.B ut many of Archimedes writings did survive, copied by scribeswho passed on his precious mathematics from generation to generation until inthe 10 th century one final copy of his the Method was made. But interest inmathematics had now died Archimedes name was forgotten then, but one day in12 th century a monk ran out of parchment. The paper were reused to make aprayer book, the page was washed or scraped clean enough so that it would bethen possible to write over them. The manuscript was become whats known as


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palimpsest. A t last science had advanced far enough for scholars to re-discover& understand the Archimedes surviving works. Renaissance mathematicians had tograpple with concepts & problems that Archimedes had worked out centuriesbefore. If mathematicians & scientists of Renaissance had been aware of thesediscoveries of Archimedes that could have a tremendous impact on developmentof mathematics. T he book Method revealed that Archimedes had

come up with a radical approach that nomathematicians had come close to inventing. In hishead he dreamt up entirely imaginary scales tocompare the volumes of curve shapes he used this totry & work out the volume of sphere. Using verycomplex mathematics in his head in which he imaginedcutting the shapes into an infinite number of slices &summing all the slices. The final result after all the arithmetic was done was thevolume of sphere is precisely 2/3 rd of the volume of the cylinder that enclosed thesphere; it is an important mathematical discovery.W orking out volumes using infinite slicing suggested by the

Archimedes was taking the first step towards the vital branch of mathematicsknown as calculus 1800 years before it was invented. Building on Archimedesdiscoveries scientists beginning with Newton & Gottfried Leibnizcreated thecalculus we know today I t was Archimedes work with infinity thatultimately let him to the beginning of calculus. The new findings reveal thatArchimedes was more sophisticated & closer to modern science than any one wasrealized. P erhaps the most interesting question of all is what might havehappen if this document had not been lost for a millennium suppose it wasavailable to those mathematicians of the Renaissance; who knows how differentmodern world might look.So the on ly way to create interest among the students is to explainthem the history of electricity; like how electricity became an essential part of ourlife, who are the great personalities contributed for the development of this field,what are the struggles they have overcome in their journey, many more factswhich have been revealed & the facts which are buried beneath the earth, thesecrets in the history of electricity. So here we have made an effort to present all


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B eginningB efore the nineteenth century, electricity was a scienceof sparks & shocks. Most early experiments wereintended to display this mysterious power of nature inthe most spectacular fashion possible or to bring out thestrange subtleties of its action. The history of theadvancement of science shows that its progress has notlacked continuity. No one man, or no generation ofmen, can be justly credited with all that is involved inany one of the great inventions or memorablediscoveries with which science has enriched the world.All have built upon the labours of their predecessor, & to understand thecompleted work it is necessary to know something of the history of its variousstages. The initial ideathe germfound its lodgement in some brain

existing at an epoch far beyond the limits of history. As stated already theexistence of Electricity was observed as lightning in the skies since the beginning ofthe universe, even before there was life on earth. There are evidences that peoplewere aware of electricity as far back as 600 BC. Thales of Miletus, father ofIonic philosophy is thought to be the first to study about the creation of electricalenergy. While experimenting with amber rods, Thales found that, after rubbingthem, they attracted lightweight objects.The dates of Thales' life are not known precisely. The time of his lifeis roughly established by a few dateable events mentioned in the sources and anestimate of his length of life. Thales involved himself in many activities, taking therole of an innovator. Some say that he left no writings, others that which he wrote"On the Solstice" and "On the Equinox" neither have survived. Many investigatorswere fascinated with lodestone & over the years many experiments wereconducted w ith it.In the 11th century, the Chinese scientist Shen Kuo (10311095)was the first person to write of the magnetic needle compass and that it improvedthe accuracy of navigation by employing the astronomical concept of true north(Dream Pool Essays, AD 1088 ), and by the 12th century the Chinese were knownto use the lodestone compass for navigation.


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I t wasn't until 1600A.D. that Thales' study wassignificantly expanded upon. While many werecurious about electricity, no one made anysubstantial advancement in the field until anEnglishman named William Gilbert studiedelectricity along with magnetism and argued thatthey were not the same thing.G ilbert, also known as William of Colchester,performed important early studies of Electricity andMagnetism. He spent 17 years experimenting with Magnetism and, to a lesser

extent, Electricity. For his work on magnets, Gilbert is known as the F ath er ofMagnetism. He was the founder of the modern sciences of Electricity andMagnetism. He discovered various methods for producing and strengtheningmagnets. For example, he found that when a steel rod was stroked by a naturalmagnet the rod it became a magnet, and that an iron bar aligned in the magneticfield of the earth for a long period of time gradually developed magneticproperties of its own. In addition, he observed that the magnetism of a piece ofmaterial was destroyed when the m aterial was sufficiently heated.D e M agnete

In his famous book De Magnete (1600), he was the first todescribe the earth's magnetic field and to assume the relationship betweenelectricity and magnetism. This is one of the great classics of experimental physics.


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H e also wrote about the electrification of many substances in hisbook. He first coined the term Electricity from the Greek word for amber.Gilbert was among the first to divide substances into Electrics (spar, glass, amber)and Non-electrics. He was also the first person to use the terms Electric force,Magnetic pole, and Electric attraction. William Gilbert was a pioneer of theexperimental method and the first to explain the M agnetic Compass

O f his own experiments, the most important wasconducted with a magnetized "terrella" ("littleEarth"), a spherical magnet serving as a model forthe Earth. By moving a small compass over thesurface of the terrella, Gilbert reproduced thedirectional behaviour of the compass; reputedly,he also demonstrated this in front of QueenElizabeth and her court.

H e also developed Versorium. TheVersorium is a needle constructed out ofmetal which is allowed to pivot freely ona pedestal. The metal needle would beattracted to charged bodies brought nearit, turning towards the charged object.Since it is able to distinguish betweencharged and non-charged objects, it is anexample of a class of devices known as electroscopes. It can be noted that theVersorium is of a similar construction to the magnetic compass, but is influencedby electrostatic rather than magnetic forces. At the time, the differences betweenmagnetic and electrical forces were poorly understood and Gilbert did a series ofexperiments to prove they were two separate types of forces with the Versoriumand another device called a Terrella (or "little Earth").


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W hat was known before Gilbert about M agnets?The ancient Greeks knew about lodestones(sometimes spelled loadstones), a Lodestone is anaturally occurring piece of magnetic iron oxide.It is often bound in a brass frame, and is orientedto place the magnetic poles at the ends. Theword magnet comes from the region calledMagnesia in Asia Minor. The early Chinese alsoknew about lodestones and about ironmagnetized by them. Around the year 1000 theydiscovered that when a lodestone or an iron magnet was placed on a float in a

bowl of water, is always pointed north. From this developed the magneticcompass, which quickly spread to the Arabs and from them to Europe. Thecompass helped ships navigate safely, even out of sight of land, even when cloudscovered the stars. Compasses were also built into portable sundials, whosepointers had to face north to give the correct time.The nature of magnetism and the strange

directional properties of the compass were acomplete mystery. For instance, no garlic wasallowed on board ships, in the mistaken beliefthat its pungent fumes caused the compass tomalfunction. Columbusfelt the compass needlewas somehow attracted by the pole star, whichmaintained a fixed position in the northern skywhile the rest of the heavens rotated around it.Two things were noted in those centuries. First,the compass needle did not point exactly north(towards the pole star) but veered off slightly tothe east. And second, the force on the needlewas not horizontal but slanted downwards intothe Earth.


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W illiam G ilbert however explained thatthe earth actually has two sets of poles.One set of poles are the geographicpoles. The geographic poles are the endsof the imaginary axis around which theworld rotates. The other set of poles arethe magnetic poles. The magnetic poles inthe north are not in the same place as thenorth geographic pole. The location ofthe geographic poles of the earth doesnot change. However, the location of themagnetic poles of the earth change constantly, though not greatly, as time goes by.Due to the changing locations of the magnetic poles, we probably should think ofthe location of the magnetic poles as polar areas rather than exact points.P reviously to the announcement of Dr. Gilberts discoveries, the

only known e lectrics were amber, tourmaline, & jet, the accessions he made to thenumber must be regarded as an important first step in the progress of electricity.He added at least twenty to the list of electrics, including most of the preciousstones, glass. Sulphur, sealing-wax, & resin; & he determined that those substances,when rubbed under favourable circumstances, attract not only light floatingbodies, but all solid matters whatever, including metals, water, & oil. He observedalso that the conditions most favourable to the excitement of attractive powerare, a dry state of the atmosphere, & a brisk & light friction; whilst moist air & asoutherly wind he found to be most prejudicial to the production of electricaleffects. W illiam Gilbert died on 30 November 1603 and was buried inHoly Trinity, an Anglican church, in Colchester where a monument was erected tohis memory. The Gilbert (Gi) is the CGS unit of Magneto motive force, equal to10/4p = 0.795 775 ampere-turns, is named for him in honour.G ilbert's experiments led to a number of investigations by manypioneers in the development of electricity technology over the next 350 years.Many seventeenth-century scientists would discover rudimentary electricalphenomena & would take to rubbing electrics after reading De- Magnete.A fter the discoveries & investigations of this father of electricsciences, there was a lapse of about many years with scarcely any progress.


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W e all know that compass will always pointtoward the North Pole. But what makes a compasswork the way it does? And why is it useful fordetecting small magnetic fields.

A compass is an extremely simple device. A magnetic compassconsists of a small, light weight magnet balanced on a nearly frictionless pivotpoint.

E arth's Magnetic Field T he reason why a compass works is moreinteresting. It turns out that you can thinkof the Earth as having a gigantic barmagnet buried inside. In order for thenorth end of the compass to point towardthe North Pole, you have to assume thatthe buried bar magnet has its south end atthe North Pole, as shown in the diagram atthe left. If you think of the world this way,then you can see that the normal oppositesattract rule of magnets would cause the

north end of the compass needle to point toward the south end of the buried barmagnet. So the compass points toward the North Pole.

The magnetic field of the Earth is fairly weak on the surface. Afterall, the planet Earth is almost 8,000 m iles in diameter, so the magnetic field has totravel a long way to affect your compass. That is why a compass needs to have alightweight magnet and a frictionless bearing. Otherwise, there just isn't enoughstrength in the Earth's magnetic field to turn the needle.


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T he "big bar magnet buried in thecore" analogy works to explain whythe Earth has a magnetic field, butobviously that is not what is reallyhappening. So what s reallyhappening?T here are very complicated theoriesto explain, but there is a workingtheory currently making the rounds.As seen on the left, the Earth's core isthought to consist largely of molteniron (red). But at the very core, thepressure is so great that this superhot iron crystallizes into a solid. Convectioncaused by heat radiating from the core, along with the rotation of the Earth,causes the liquid iron to move in a rotational pattern. It is believed that theserotational forces in the liquid iron layer lead to weak magnetic forces around theaxis of spin. I t turns out that because the Earth's magnetic field is so weak, a

compass is nothing but a detector for very slight magnetic fields created byanything. That is why we can use a compass to detect the small magnetic fieldproduced by a w ire carrying a current.

ource H ow stuff workshttp://adventure.howstuffworks.com/outdoor-activities/hiking/compass1.htm


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B irth of first Electrical G eneratorThe most important advances in the science after Gilbert weremade by a German physicist, engineer and natural philosopher Otto VonGuericke who built the first machine to create an electric spark. He used thiselectrical generator for many experiments with electricity; He invent ed the first airpump and used it to study the phenomenon of vacuum and the role of air incombustion and respiration.

On November 20, 1602, Otto Guericke was born asson of a patrician family resident in Magdeburg.Guericke studied astronomy and as a convincedCopernican, von Guericke was concerned with thenature of space and the possibility of empty spaceand the means of action across it. Guericke wasconducting several scientific experiments in his yard.He become interested in the atmosphere, thus hestudied the work of Galileo and Torricelli.

H e made his first suction pump in 1647 andcontinued in the following years to work atimproving it into a real air pump. In 1650 heinvented the air pump, which he used to create apartial vacuum. Guericke used his pumps to studyvacuums and the role of air in combustion andrespiration. Otto van Guericke made several veryspectacular experiments with his air pumps. In 1654Guericke placed two copper bowls (Magdeburghemispheres) together to form a hollow sphereabout 35.5 cm (14 inches) in diameter. After he hadremoved the air from the sphere, two teams of eighthorses were unable to pull the bowls apart, eventhough they were held together only by the airaround them. Thus the tremendous force that air pressure exerts was firstdemonstrated.


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G uericke used his air pumps for many other experiments includingexperiments with electricity and magnetism. He proved that a lodestone, ormagnet, can attract iron even in a vacuum; and that electrical attraction works ina vacuum as well. Air is needed by neither magnets nor electrics. It was a greatbreakthrough.G uericke's electric generatorsThe apparatus with which electricians had experimented till nearthe end of the seventeenth century w as of the simplest kind. A rod or flat surfaceof glass, resin, or sulphur, rubbed with the hand or with a piece of woo llen, wastheir best means of exciting electricity; it may therefore be supposed that thequantity at any time under observation was very small. In 1663 Otto vanGuericke invented the first electric generator, which produced static electricity byapplying friction in the machine. The generator was made of a large sulphur ballcast inside a glass globe, mounted on a shaft. The ball was rotated by means of acrank and a static electric spark was produced when a pad was rubbed against theball as it rotated. The globe cou ld be removed and used as source for experimentswith electricity.


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L ater editions increased the speed of the rotation with a belt androtating wheel. Electrical demonstrations became a favourite parlour trick forguests, but the electric machine also allowed scientists to perform experiments thatcould not be performed earlier.


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In 1740 von Bose, a professor of physics at Wittemberg,substituted glass for the sulphur, and improved the rotating mechanism. He alsosuspended a metal cylinder above the globe by silk strings, with a metallic chain toconduct the electricity from the globe to the cylinder. This method of collecting isshown in figure above. From that time the electrical machine evolved rapidly.First, the shape of the rubbed body was modified: Watson employed four glassglobes; Wilson, Cavallo, and Nairne used cylinders instead of spheres, Sigaud de laFond, Le Roy, Cuthbertson, Van Marum, and Ramsden, used plates of glass insteadof cylinders or globes. This allowed a larger surface area to be rubbed, andincreased the speed of rotation. G uericke published all his discoveries in a

book titled Experimenta nova Magdeburgicade vacuo spatio . This remarkable work onexperimental philosophy ranks next to G ilbert'sin the number and importance of the electricaldiscoveries described.

The only property of electricity then known was that of attraction.Otto Von Guericke must also be conferred the honour of having discovered theproperty of electric repulsion. He ascertained that a feather, when attracted to anexcited electric, after adhering to it for a short time, is repelled from the surface,& that it will not again approach until it has touched some other body to which itcan part with the electricity it contains. He observed, also, that a feather whenthus repelled by an excited electric, always keeps the same side presented towardsit. As there was a correspondence between this fact & the position of the moontowards the earth, it was assumed that the revolution of the moon round theearth may be caused by electric attraction or repulsion. The discoveries of Sir IsaacNewton, shortly afterwards, dispelled this notion, & so far engaged the attentionof scientific inquirers, that electricity for a time remained in abeyance.Source:

John JenkinsSpark Museum Wikipedia http://en.wikipedia.org/wiki/Otto_von_Guericke


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E lectroluminescenceFrancis Hauksbee was English physicist who

wrote a famous book Physico-MechanicalExperiments on Various Subjects. Containing anAccount of Several Surprising PhenomenaTouching Light and Electricity in 1709. It is oneof the most important works in early electricity thatintroduced several new concepts and discoveries.He also invented a glass sphere, turned by a crank,which could build up an electric charge throughfriction.H e was also the first to study capillary action. Little is known of

Francis Hauksbees life; even the dates of his birth and death are not documented.He also made and sold instruments e.g., cupping glasses used in surgery, airpumps, and barometers. He developed an improved air pump (though no oneseems able to define precisely what Hauksbees improvements were), and whatwas, in effect, the first static electric or frictional electric machine, a glass globemounted on an axle (1706), and also a primitive electroscope todetect electric charges.H auksbee determined with reasonable accuracy the relative weightsof air and water. Investigating the forces of surface tension, he made the firstaccurate observations on the capillary action of tubes and glass plates. He alsomade experiments on the propagation of sound in compressed and rarefied air, onfreezing of water, and on elastic rebound. He measured specific gravities andrefractive indices. He investigated the law of magnetic attraction and the time offall through air.F rancis Hauksbee discovered that by putting a small amount ofmercury in the glass of Von Guerickes generator and evacuating the air from it,when a charge was built up on the ba ll and then his hand placed onto it, it wouldglow. This glow was enough to read by and was similar to the phenomenonknown as St. Elmos Fire which was the name given to a strange glow seen aroun dships in electrical storms.


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St. Elmo's fire(also St. Elmo's light) isan electrical weather phenomenon in whichluminous plasma is created by a coronaldischarge originating from a grounded object inatmospheric electric field (such as those generatedby thunderstorms created by a volcanic explosion).

S t. Elmo's fire is named after St. Erasmus of Formiae (also called St.Elmo, the Italian name for St. Erasmus), the patron saint of sailors. Thephenomenon sometimes appeared on ships at sea during thunderstorms and wasregarded by sailors with religious awe for its glowing ball of light, accounting forthe name. S t. Elmo's fire is, in fact, a mixture of gas and plasma (asare flames in general, and also stars). The electric field around the object inquestion causes ionization of the air molecules, producing a faint glow easilyvisible in low-light conditions. Approximately 1000 volts a centimeter induces St.Elmo's fire; however, this number is greatly dependent on the geometry of theobject in question. Sharp points tend to require lower voltage levels to producethe same result because electric fields are more concentrated in areas ofhigh curvature, thus discharges are more intense at the end of pointed objects.Conditions that can generate St. Elmo's fire are present duringthunderstorms, when high voltage is present between clouds and the groundunderneath, electrically charged. Air molecules glow due to the effects of suchvoltage, producing St. Elmo's fire.The nitrogen and oxygen in the Earth's atmosphere causes St. Elmo'sfire to fluoresce with blue or violet light; this is similar to the mechanism thatcauses neon lights to glow.

Source: Wikipedia http://en.wikipedia.org/wiki/St._Elmo%27s_fire


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Early Electric Machines(Static Electricity Generators)

Source: John Jenkins Spark Museum Wikipedia http://en.wikipedia.org/wiki/Electrostatic_generator

A n electric machine consists of thecombination of two materials, which whenrubbed together produce static electricity,and of a third material or object which actsas a collector for the charges.The first devices for producing electricitywere very simple. The ancient Greeksdiscovered the strange effects of amberrubbed with fur and other material. In the17th century, scientists used sticks of resin orsealing wax, glass tubes and other objects.By the time of Benjamin Franklin large glasstubes about three feet long and from an inch to an inch and a half in diameterwere popular; these were rubbed either with a dry hand or with brown paperdried at the fire.T here are two major categories of electrical machines: Friction

and Influence. A friction machine generates static electricity by direct physicalcontact; the glass sphere, cylinder or plate is rubbed by a pad as it passes by.Influence machines, on the other hand, have no physical contact. The chargeis produced by inductance; usually between two or more glass plates. Thecharge could then be stored in a Leyden jar or measured by an electroscope.


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R amsden M achineO ne of the earliest and certainly classicfriction machines is the Ramsden machine.A large circular plate of glass is mountedvertically on a metal axle, about which itcan easily be turned by a crank handle.When passing between the two woodensupports, the surface of the glass is rubbedby two pairs of pads fixed to the supports. The rotation of the glass then causesit to become electrified positively on both faces. The negative charge of thepads is neutralized by being connected to the ground through the frame, which isnot insulated. Each pad is stuffed with hair, and is covered with leather: Itssurface is coated with mosaic gold, or an amalgam of mercury with zinc,bismuth, or tin. Attached to the pads are silk cases which enclose the glass platenearly as far as the combs, these are to prevent loss of charge.

In 1772 Le Roy, a French physicist,constructed a glass plate machine withonly one pair of pads; he had howeverused two insulated cylindrical conductorsplaced horizontally at opposite ends of adiameter, one attached to the pads andthe other to the metallic comb, thus hecollected both kinds of charge. Winter, anAustrian, slightly modified Le Roy's machine to a form shown in Fig above. Theconductors are spheres; one is attached to the pads whilst the other is connectedto 'the combs, constructed as two rings, one on each side of the glass. Oneconductor is charged positively, the other negatively. Winter's machine does notgive a large quantity of electricity at each discharge, on account of the small sizeof the conductor, but it gives longer sparks than the other forms of machine of thesame size.


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W imshurst M achineW imshurst machines are the end point ofthe long development of electrostatic diskmachines. They caused very good results andwere frequently used to power X-ray tubes.The characteristic construction element ofthese machines are disks which are laminatedwith radially arranged metal sheets. Theadvantage of d isks is that they can be stackedonto one axle in order to multiply the effect.

A ll through the 18th and 19 th centuries therewas tremendous interest in electricity. Scientists such as Franklin, Nollet, Coulomb,Volta, Oersted, Ampre, Ohm, Faraday, Joule and others made major advances.Prior to Faraday's invention of the induction coil in 1831 however, the only wayto generate high voltage electricity was via a static generator such as those statedabove.


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W hy 50H z power supply is standard in all countries?T he reason is that this is in the optimum range forpower supply on a national scale. The use of lowerfrequencies would cause the size, weight and cost ofthe installed equipment to increase and the flicker oflights to become noticeable (as it was on early25Hz systems). The use of higher frequencies wouldcause increase in the operational losses due to eddycurrents, hy stere sis, skin effect, radiation etc. and reactive vo ltage drops.In physically smaller power systems such as those on planes, ships,

submarines and even railways, higher frequencies are used because they allowreduction in the power equipment size and weight - i.e. the optimisation isdifferent. S ystem frequency is standardized for economic reasons - if the samefrequency is used over a wide area, then it is possible to interconnect systems.That makes it possible to share reserve energy supplies across that area resulting inlower costs and improved reliability for everyone.

50 Hz however, is not universal. Many countries use 60 Hz which isclose to the same optimum as 50. 60 Hz users mainly are: almost all the Americasand some countries in Asia. Korea even uses both frequencies 50 Hz prevails inEurope and ex-British colonies.In the very early days of electrification, electrical loads were servedby dedicated generation, so designers selected the frequency that they felt wouldresult in the optimum design for loads and generation. Some of the early systemshad frequencies as high as 135Hz. eventually, as the desire for interconnectionemerged, it became necessary to standardize on a single frequency. The choicebetween 50Hz and 60Hz ultimately came down to the kind of lighting that wasin widespread use in the region being served. In Europe, the prevailing practice(driven mainly by Siemens) was to use an enclosed-arc form of lighting at 50Hz.In North America, the practice was to use an exposed arc for m of lighting.Because the extinction time con stant was shorter when the arc was exposed, therewas a desire to supply those lights with a voltage that had a shorter periodbetween zero crossings (to prevent 'flickering') - hence, the choice of 60Hz.


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F irst experiment to show Electric Power can be transmitted over long distanceH owever, despite the enormity of scientificadvancement during the seventeenth century, the laws ofelectricity stayed just out of reach. All this was about tochange. Before the century was over, electricity wouldbecome a popular science with significant body ofknowledge & many practical applications. The mostardent student of electricity in the early years of theeighteenth century was Stephen Gray. He performed amultitude of experiments, nearly all of which addedsomething to the rapidly accumulating stock of

knowledge, but doubtless his most important contribution was his discovery ofthe distinction between conductors & non-conductors.S tephen Gray was born in Canterbury, Kent, England on December26th 1666. His friendship with John Flamsteed most likely fired his interests inastronomy. From the 1690s to 1716 Gray devoted his scientific energies toastronomical observations. In the latter years of his life he devoted himself toelectricity. His electrical interests first appear in a letter of 1708 to Hans Sloane, inwhich he described the use of down feathers to detect electricity. He is obviouslyfascinated by lights produced by rubbing a glass tube to charge it and realizeselectricity and the lights are related. The idea of an effluvium released from thetube is giving way in his thoughts to ideas of a virtue, something akin togravitational attraction and electrical conduction.G ray's ApparatusF or his experiments, Gray used a simple 3.5 foot glass tube, 1.2" indiameter. When rubbed with a dry hand or dry paper the glass would obtain anelectric charge. These glass tubes were popular - they were much more portableand less expensive and than the large electrical m achines of the time.G ray begins with some background on his reason for conductingthese experiments he tells how he became interested in whether electric effluvia(scientists of the time believed electricity was a fluid) could be communicatedbetween charged objects . This question came up as a result of his observationthat his tube comm unicated light to bodies , i.e. he saw sparks jump from the tubeto objects held near it.


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H e notices that the charged tube not only attracts a feather to theglass, but to the cork as well. From this he concludes that the "attractive virtue" ispassed to the cork from the tube. Being a diligent observer, Gray proceeds toexamine exactly how far the virtue can be passed. He attaches an ivory ball to afour inch piece of wood and inserts the other end of the wood into the cork. Hefinds that not only is the attraction and repulsion passed to the ball, it is evenstronger than on the cork. So by accident Gray discovered one of the amazingphenomena that electricity can be transmitted to long distances , but how long iswhat Gray tries to find with his later experiments.T he first use of metal w ireG ray proceeds to try other materials between the tube and theivory ball. He tries iron and brass wire which does pass the virtue, but vibrationof the wire caused by rubbing the tube interferes with the experiment. So Grayuses pack-thread in place of the wire, and inserts a loop to absorb the vibrationsof the tube. Again, he finds the effluvia is passed to the ball.G ray searched around his house for any object that might besuitable for a test. He focused on metals first, testing several coins, pieces of tinand lead, a fire-shovel, tongs and iron poker, a tea-kettle (both empty and full,hot and cold water ) and a silver pint-pot. He found all of them to beconductive. Next he searched out what non-metal objects he could find,including several types of stone and some green vegetables, all of which hesystematically hung from his harness of pack-thread, and all of which passed the attractive virtue.Over the next several days, Gray continued to experiment byextending the length of his apparatus, these experiments were performedvertically; that is, the assembly of rods, pack-thread, wire, etc., was hung verticallywith the ivory ball at the bottom and the glass tube at the top. Gray did this outof simple practicality (hanging the thread required no supports to hold it abovethe floor, unlike a horizontal run would require), not because he believed theeffluvia needed to run downhill. In any case, he extended his apparatus higherand higher, from 26 feet until he was as high as he could go on his balcony andstill the virtues were carried the full 52 feet.


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A horizontal runS ince he had reached the upper limits of the house, the next logicalstep was to run the thread horizontally. He attached one end of the thread to anail in a beam and the other end looped over the tube. This time when he rubbedthe tube nothing happened. He correctly concludes that the fault is in theconnection from the thread through the nail to the beam; i.e. the 'electrical virtue"is passing into the beam rather than being carried to the ivory ball. His experimentwas unsuccessful because he suspended the line by threads that conducted theelectricity from it nearly as quickly as it entered.A t this point he decided to give up on the horizontal approach andperform more experiments with a vertical conductor. But where was he to find abuilding tall enough? Gray visited his young friend Granville Wheeler, who livedin a large house that would be very suitable for further tests. After severalsuccessful attempts, and reaching the highest point of the house, Wheelersuggested they try a horizontal span. Gray explained that his previous attempt hadfailed, and his theory as to why. It was then suggested by Mr. Wheeler, that causeof the escape of electricity was the thickness of the packthread employed, & herecommended that silk threads should be tried, because being much thinner, it wassupposed the electric fluid would not be able to flow through it so readily Grayagreed this was worth a try, thinking that less of the electric virtue would leak outthrough the small silk thread.On July 2, 1729, they assembled the experiment shown in Fig.below, using silk thread and poles to hold the packing thread above theground. With a run of 80.5 feet, the leaf-brass was attracted to the ivory ball.


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G ray and his friend, conducted experiments which showed thatobjects such as cork, as far as eight or nine hundred feet away, could be electrifiedby connecting them to the glass tube with wires or hempen string. They foundmaterial such as silk would not convey electricity. They discovered distant objectscould not be electrified if the transm ission line m ade contact w ith earth. The line fortransmission was suspended by silk threads to prevent contact with the ground. Itwas found that metal objects held in the hand and rubbed showed no signs ofelectrification. However, when mounted on a non-conductor, they becameelectrified. Gray realized that somehow the earth was responsible for conductingelectrical charge away from the body. After this realization Gray found he couldelectrify any material on earth by friction.

S o little were exp erimenters aw are that the difference in the effectswa s caused by the different conducting properties of the substances employed.W ith the notion that success with the silk suspenders was entirely owing to theirsuperior fineness, that they endeavou red to obtain still better results by suspendingthe line on very fine wires. Th e total failure of experiment in this case induced themat length to consider that there m ust be a difference in the conducting prope rties ofthe substances employed.The attention of electricians thus directed to this subject, list ofconducting & non-conducting substances were made, when it was found thatglass, resin, & all bodies known electrics, were bad conductors of electricity, & thatthose in which electricity could be excited were conductors. In the conducting &non-conducting properties of these substances great differences was soondetected; glass & resin being the worst, & metals the best conductors.

G rey sent many of his papers to the Royal Society, Gray's mostimportant work, published in 1732, announced the discovery of electricalinduction and the distinction between conductors and insulators. Despite the factimportance of his discoveries he received little credit at the time of his discoveriesbecause of the factional dispute in the Royal Society, and the dominance ofNewtonianism (which became the Masonic 'ideology'). By the time his discoverieswere publicly recognized, experiments in electricity had moved rapidly on and hispast discoveries tended to look trivial. For this reason, some historians tend tooverlook his work.There is no monument to Gray, and little recognition of what heachieved, against all odds, in his scientific discoveries.


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Some Gray's papers fell into the hands of Charles Franois deCisternay du Fay, an officer of the French army, who, after several yearsservice; he had resigned his post to devote himself to scientific pursuits. Herepeated many of the experiments described by the Englishman, & became anenthusiastic student of the science. His work shows great acuteness of mind, aswell as remarkable experimental skill. He made a critical examination of a curiousexperiment made by Gray, in which it appears that the colour of bodiesinfluenced their susceptibility to electrical disturbance.H e had detected the existence of two distinct kinds of

Electricity. This, like all other discoveries hitherto made,originated from accidental circumstances. A piece ofgold-leaf having been repelled from an excited glass rod,M. Du Fay pursued it with an excited rod of sealing-wax,expecting that the gold-leaf would be equally repelledby that electric; but he was astonished to see it, on thecontrary, attracted to the wax. On repeating theexperiment he found the same result invariably tofollow: the gold-leaf when repelled from glass wasattracted by resin; and when repelled by the latter was attracted by glass. HenceM. Du Fay assumed that the electricity excited by the two substances was of

different kinds; and as one was produced from glass, the other from resin, hedistinguished them by the names VITREOUS and RESINOUS electricity.A t the time, there was a storage device named the Leyden jar. Thiswas a glass jar, partially filled with water, and covered inside and out with tin foil.A wire ran through a cork stopper and, as electricity was generated, it passedthrough the wire into the jar, where it was stored. Since the Leyden jar could storea fairly large amount of electricity, Du Fay was able to perform some interesting(and potentially deadly) demonstrations. In one, he passed an electrical dischargethrough 180 soldiers who had joined hands in a circle (which also gave rise to theterm "Circuit") by having the first soldier hold the jar and the last soldier touch thecenter wire. He (and others) apparently enjoyed themselves greatly, chargingLeyden jars and shocking their friends and relatives. Unfortunately, they did notknow that such shocks could be deadly.


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One of the experiments devised about this period, which excitedgreat astonishment, & tended to direct the attention of philosophic inquirers tothe subject of electricity, was the development of sparks from the human body.Mr. Grey suspended a boy horizontally with hair lines, & communicated electricityto him by means of an excited glass tube, and then sparks were drawn from allparts of boys body. This phenomenon, depending simply on the fact that thebodies of animals are conductors of electricity in consequence of the fluids theycontain, was conceived to owe, in some mysterious manner, to a connectionbetween the electric effluvium, as it was called, and the vital principle. M. Du Faysuspended himself in a similar manner for the purpose of experiencing thesensation, & the experiment soon afterwards became the most popular in therange of electrical phenomenon, when the more convenient mode of insulationby standing on a cake of resin, or on a glass stool, was introduced.W ater is found to be a conductor. It renders insulators conductingwhen the surfaces are wet or m oist. This makes understandable the rapid loss ofcharge by electrified bodies on hum id days.In the last years of his life Du Fay did his work on the opticalproperties of crystals. Du Fay had taken the first steps toward a correlation ofcrystal form and optical properties. Unfortunately his early death prevented thefull publication of his results. Du Fay died on July 16, 1739, after a brief illness. DuFay's work was influential in Benjamin Franklin's later work with electricity, and healso influenced many other prominent scientists of the day.Source:

Wikipedia http://en.wikipedia.org/wiki/Stephen_Gray_(scientist) John Jenkins Spark M useum


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T ree Rings & ClimateH ave you ever wondered how can w e predict the ageof a tree? D o you think trees are helpful in predictingthe weather conditions?

T rees contain some of nature's most accurate evidence of the past.Their growth layers, appearing as rings in the cross section of the tree trunk,record evidence of floods, droughts, insect attacks, lightning strikes, and evenearthquakes that occurred during the lifespan of the tree. Subtle changes in thethickness of the rings over time indicate changes in length of, or water availabilityduring, the growing season. E ach year, a tree adds to its girth, with the

new growth being called a tree ring. Treegrowth depends upon local environmentalconditions. In some areas the limiting factorfor growth is water availability, in otherareas (especially at high latitudes) it is thelength of the growing season. In areas wherewater is limited and the amount of watervaries from year to year, scientists can usetree-ring patterns to reconstruct regionalpatterns of drought. In areas where thelength of the growing season is the limitingfactor, the thickness of tree rings can indicatewhen growing seasons were longer (duringwarmer times) and when growing seasonswere shorter (cooler times).T he study of the growth of tree rings is known as dendrochronology .

The study of the relationship between climate and tree growth in an effort toreconstruct past climates is known as dendroclimatology .


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A tree ring consists of two layers: A light colour layer which grows in the spring A dark colour layer which forms in late summerA t locations where tree growth is limited by water availability, trees

will produce wider rings during wet and cool years than during hot and dry years.Drought or a severe winter can cause narrower rings too. If the rings are aconsistent width throughout the tree, the climate was the same year after year. B ycounting the rings of a tree, we can pretty accurately determine the age and healthof the tree and the growing season of each year .M odern dendrochronologists seldom cut down a tree to analyzeits rings. Instead, core samples are extracted using a borer that's screwed into thetree and pulled out, bringing with it a straw-size sample of wood about 4millimetres in diameter, the hole in the tree is then sealed to prevent disease.

Computer analysis and other methods have allowed scientists tobetter understand certain large-scale climatic changes that have occurred in pastcenturies. These methods also make highly localized analyses possible. Forexample, archaeologists use tree rings to date timber from log cabins and NativeAmerican pueblos by matching the rings from the cut timbers of homes to rings invery old trees nearby. Matching these patterns can show the year a tree was cut,thus revealing the age of a dwelling.T ree ring data is only collected outside of the tropics. Trees intemperate latitudes have annual spurts of growth in the summer and periods ofdormancy in the winter, which creates the distinctive pattern of light and darkbands. Tropical trees grow year-round, and thus do not have the alternating darkand light band pattern that allows us to read tree ring records.T ree ring records can be combined to create climate records thatspan a timeframe longer than the life of a single tree. For example, the data froma living, 200-year old tree could be combined with a data from wood from a treethat was felled 150 years ago (after living a couple of centuries) to produce acomposite dataset spanning several hundred years.


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T rees, alive or dead, are not the only source of wood used toconstruct such extended records. Beams from old buildings or ruins, samples fromwooden frames of old paintings, and slivers from violins have all been used toadd wood samples from trees long dead to climate chronologies. In some cases,tree rings enshrined in petrified wood even give us some insights into climateconditions in truly ancient times.The oldest trees on Earth, the bristlecone pines of western NorthAmerica, can live for more than 4,000 years. Dead bristlecone trunks, often well-preserved in the dry terrain upon which bristle cones grow, can be as much as9,000 years old.The proxy climate record preserved by tree ring data spans a period of about9,000 years. The resolution of tree ring data is one year. Tree ring records areamongst the highest resolution proxy climate data types, but they also have oneof the shortest time spans over which they app ly as compared to o ther proxies.S cientists have used tree rings, whose width can reflect climateconditions experienced during each growing season, and they have used glaciers,which accumulate a new layer of ice with each years snowfall. High -resolution icecores from Greenland have shown multiple events during the past 100,000 yearsin which air temperatures abruptly rose and fell by as much as 10C (18F) within adecade. Scientists have found clues to past oceanic conditions preserved insediment cores that accumulate in sequential layers on the seafloor.

Source:

W indow to U niversehttp://www.windows2universe.org/earth/climate/CDcourses_treerings.html


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H ere at last was sufficient electricity to produce a real stir in theworld. Writing in 1795, Cavallo says: In short nothing contributed to makeElectricity the subject of the public attention & excite a general curiosity until thecapital discovery of the vast accumulation of its power in w hat is comm only calledthe Leyden Jar, which was accidentally made in the year 1745. Then, & not tillthen, the study of electricity becam e general, surprised every beh older, & invited tothe house of electricians a greater number of spectators than were ever assembledtogether to observe any philosophical experiments whatsoever.


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B enjamin Franklin & K ite ExperimentB enjamin Franklin was one of the Founding Fathers of theUnited States. A noted polymath, Franklin was a leading author and printer,satirist, political theorist, politician, postmaster, scientist, inventor, civic activist,statesman, and diplomat. As a scientist, he was a major figure in the AmericanEnlightenment and the history of physics for his discoveries and theories regardingelectricity. He invented the lightning rod, bifocals, the Franklin stove, a carriageodometer, and the glass 'armonica'. He formed both the first public lending libraryin America and the first fire department in Pennsylvania.B enjamin Franklin was born in Boston

Massachusetts, on January 17, 1706. He was theseventh child in his family. Franklin started going toschool when he was ten, and became an apprentice tohis older brother who owned a printing firm inPhiladelphia. Even though he did not attend school fora long time, Franklin began interested in science. Hewas particularly interested in Electricity. Even thoughthere were already many experiments being conductedin this field, none of them had fully explained thephenomenon.A list of Benjamin Franklin's inventions reveals a man of many

talents and interests. It was the scientist in Ben that brought out the inventor. Hisnatural curiosity about things and the way they work made him try to find waysto make them work better.

F or example Ben had poor vision and needed glasses to read. Hegot tired of constantly taking them off and putting them back on, so he decidedto figure out a way to make his glasses let him see bo th near and far. He had twopairs of spectacles cut in half and put half of each lens in a single frame. Today, wecall them bifocals.B enjamin Franklin developed a theory that every object had an"Electrical fluid". He believed that some objects had too much of this fluid, whileothers did not. Franklin proposed that "vitreous" and "resinous" electricity werenot different types of "electrical fluid" (as electricity was called then), but the sameelectrical fluid under different pressures. He was the first to label them as positiveand negative respectively, by putting his theories together, he invented the


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electrical battery. It was made out of glass, lead plates, silk thread, and some wire.T he individual Leyden jar, the early form ofwhat is now called a capacitor, gathers anelectrical charge and stores it until it isdischarged. Franklin grouped a number of jarsinto what he described as a "battery" (usingthe military term for weapons functioningtogether). By multiplying the number ofholding vessels, a stronger charge could bestored, and more power would be availableon d ischarge.

F ranklin realized that if a piece of silk were rubbed against a glass,the glass would have a positive charge. Other scientists at that time believed thatrubbing produced electricity; however Franklin said that it was just the "Electricfluid" being transferred from the silk to the glass. This is known today as the lawof conservation of change and it is one of the basic principles of physics.Charge conservation is the principle that electric charge can neitherbe created nor destroyed. The quantity of electric charge, the amount of positivecharge minus the amount of negative charge in the universe, is always conserved.This was not a new idea, but Franklin was the first to perform anexperiment on it. He said that if a metal rod was to be placed on top of a toweror a tall building, it would be struck by lightning & holds an electrical charge.In 1752 Franklin devised another experiment to test whether or notlightning was an electric phenomenon. This seems fairly obvious to most of ustoday, but we must remember that in Franklin's day the largest sparks they couldmake were under an inch long Since lightning is several miles long it is not soobvious that they can be the same.Can you remember the first time you ever saw a lightning bolt in a dark, stormysky? The awesome power of a lightning strike is etched into your memory.Without scientific understanding, lightning is frightening.Early cultures relied on myth and magic to explain lightning and to ease their fears.The ancient Greeks, for example, believed that the king of all the gods, Zeus,threw lightning down from the heavens to show his anger at the people below.Lightning was his weapon.As the study of weather science progressed, people stopped thinking of


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The purpose of lightning rods is often misunderstood. Many peoplebelieve that lightning rods "attract" lightning. It is better stated to say that lightningrods provide a low-resistance path to ground that can be used to conduct theenormous electrical currents when lightning strikes occur. If lightning strikes, thesystem attempts to carry the harmful electrical current away from the structureand safely to ground. The system has the ability to handle the enormous electricalcurrent associated with the strike. If the strike contacts a material that is not agood conductor, the material will suffer massive heat damage. The lightning-rodsystem is an excellent conductor and thus allows the current to flow to groundwithout causing any heat damage.

Did You Know?Rubber tires aren't why you're safe in a car during a lightning storm. Instrong electric fields, rubber tires actually become more conductive thaninsulating. You're safe in a car because the lightning will travel around thesurface of the vehicle and then go to ground. This occurs because thevehicle acts like a Faraday cage. Michael Faraday, a British physicist,discovered that a metal cage would shield objects within the cage when ahigh potential discharge hit the cage. The metal, being a good conductor,would direct the current around the objects and discharge it safely to theground. This process of shielding is widely used today to protect theelectrostatic sensitive integrated circuits in the electronics world.


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F ranklins Lightning BellsB en also developed another device tohelp him understand electricity. Called"lightning bells," the bells would jinglewhen lightning was in the air. To makethese lightning bells work, Franklin usedthe lightning rod he had erected on hisroof and ran a wire from it into hishouse. He divided the wire into twowires, which were attached to two smallbells separated by 6 inches. Between the

bells was a little brass ball, suspended by a silk thread. When storm clouds passedwith electricity in them, the ball would go back and forth, ringing the bells.This setup was used by Franklin to collect electric charge for use inother experiments. The amount of charge collected was sometimes so faint thatafter a spark between the bells it would take considerable time to charge up again.At other times a continuous stream of sparks could be obtained even at lengths ofaround 20cm. These sparks could very dangerous and a direct strike to thelightning rod could cause explosions and fire.F ranklin published his theories in a book titled Experiments &observations on Electricity made at Philadelphia. It became best seller in Europeas well as in the colonies. The main topic of this book was Franklins theory thatlightning was electrical energy.F ranklins Electric Stove :

A nother well-known invention of BenjaminFranklin was the Open stove, often called the"Franklin Stove". In 1742, he created a stove whichwould provide better warming of rooms and at thesame time save fuel. It was based on the modelsconstructed by Robert Grace, one of Franklin'sfriends.


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D uring Ben's lifetime, he made eight voyages across the AtlanticOcean. These long journeys gave him a lot of time to learn about ships and howthey worked. As early as 1784, Franklin suggested following the Chinese model ofdividing ships' holds into watertight compartments so that if a leak occurred inone compartment, the water would not spread throughout and sink the ship.Throughout his life Benjamin Franklin made many importantdiscoveries & theories which greatly influenced future scientists & inventors.Later,other famous inventors, like Thomas A. Edison and Alexander Graham Bell,would follow in Ben's footsteps by trying to find w ays to help people live better.Today's curious thinkers are keeping Ben's traditions alive by inventing new andimproved ways to make things work.

F ranklin wrote in his autobiography, As we enjoy great advantagesfrom the inventions of others, we should be glad of an opportunity to serveothers by any invention of ours; & this we should do freely & generously.F ranklin's contributions to the science of electricity were numerous& comprehensive. His experiments were wisely planned & skilfully executed. Hisdiscussion of principles & his elaboration of hypotheses were characterized by thatsimplicity & clearness which made his writings upon all subjects the admiration ofhis own & future generations.

Source:

The F ranklin Institutehttp://www.fi.edu/franklin/inventor/inventor.html John Jenkins Spark M useum


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W hat is the speed of electricity?H ave you ever thought; how fast does electricitytravel? Does it travel more than speed of light orfaster than sound? By the 1740s, WilliamWatson had conducted several experiments todetermine the speed of electricity. The generalbelief at the time was that electricity was fasterthan sound, but no accurate test been devised tomeasure the velocity of a current. Watson, in thefields north of London, laid out a line of wiresupported by dry sticks and silk which ran for12,276 feet (3.7 km). Even at this length, thevelocity of electricity seemed instantaneous.Resistance in the wire was also noticed butapparently not fully understood, as Watson related that "we observed again, thatalthough the electrical compositions were very severe to those who held thewires, the report of the Explosion at the prime Conductor was little, incomparison of that which is heard when the Circuit is short." Watson eventuallydecided not to pursue his electrical experiments, concentrating instead upon hismedical career but he continued to support others in presenting evidence to the

Royal Society T hen Charles Wheatstone an Englishscient ist renown by a great experiment themeasurement of the velocity of electricity in awire. He cut the wire at the middle, to form agap which a spark might leap across, andconnected its ends to the poles of a Leyden jar.Three sparks were thus produced, one at eitherend of the wire, and another at the middle. Hemounted a tiny mirror on the works of a watch,so that it revolved at a high velocity, andobserved the reflections of his three sparks in it.The points of the wire were so arranged that ifthe sparks were instantaneous, their reflectionswould appear in one straight line; but the middle one was seen to lag behind theothers, because it was an instant later. The electricity had taken a certain time totravel from the ends of the wire to the middle. This time was found by measuringthe amount of lag, and comparing it with the known velocity of the mirror.Having got the time, he had only to compare that with the length of half the


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wire, and he could find the velocity of electricity. However experimental orcalculation error led him to conclude that this velocity was 4,63,491 km persecond, an impossible value as it is faster than the speed of light.

T ill then, many people had considered the electric discharge to beinstantaneous; but it was afterwards found that its velocity depended on thenature of the conductor, its resistance, and its electro-static capacity. MichaelFaradayshowed, for example, that its velocity in a submarine wire, coated withinsulator and surrounded with water, is only 144,000 miles per second(232,000 km/s), or still less. Wheat stones device of the revolving mirror wasafterwards employed by Leon Foucault and Hippolyte Fizeau to measure thevelocity of light.

Source:

Wikipedia http://en.wikipedia.org/wiki/Charles_Wheatstone John Jenkins Spark M useum


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Electroscopes & ElectrometersThe first Voltmeters

T he term electroscope is given to instruments which serve twoprimary purposes: 1) to determine if a body is electrified, and 2) to determine thenature of the electrification. An electrometer, on the other hand, is a specializedform of electroscope that includes a calibrated scale for reading the strength of thecharge.

T he first electroscope was a device calleda Versorium, developed in 1600 byWilliam Gilbert. The Versorium wassimply a metal needle allowed to pivotfreely on a pedestal. The metal would be attracted to charged bodies brought

near. A simple hanging thread - called a Pendulous thread was introducedaround 1731 by Stephen Gray. The thread would be attracted to any electrifiedbody nearby.

In 1753 John Canton improved the electroscopeby adding two small pith balls suspended by finelinen thread. The upper ends of the threads werefastened inside a wooden box. When placed in thepresence of a charged body, the two balls wouldbecome similarly charged, and since like chargesrepel, the balls would separate. The degree ofseparation was a rough indicator of the amount ofcharge.


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In 1779 Tiberius Cavallo (1749-1809) designed animproved electroscope, his pocket electrometer . Thedevice included several improvements including, for thefirst time, enclosing the strings and corks inside a glassenclosure to reduce the effect of air currents.

G old-leaf electroscopeT he gold-leaf electroscope was developed in1787 by British clergyman and physicistAbraham Bennet, as a more sensitiveinstrument than pith ba ll or straw bladeelectroscopes then in use.

E lectrometersThe first true electrometer came from Horace Benedict de Saussure

(1740-1799) who placed the strings and balls inside an inverted glass jar andadded a printed scale so that the distance or angle between the balls could bemeasured. It was de Saussure who discovered the distance between the balls wasnot linearly related to the amount of charge. However, the exact "inverse square"relationship would be left for Charles Coulombto discover in 1784.In 1770, William Henley developed the first portable quadrant

electrometer. The date is sometimes referenced as 1772 since that wasthe first time the invention was published. The device consisted of aninsulated stem with an ivory or brass quadrant scale attached. A lightrod or straw extended from the center of the arc , terminating in a pith


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ball which hung touching the brass base of the electrometer. When the brass waselectrified the ball would move away from the base, producing an angle whichcould be read off of the scale.

E arly Qu adrant E lectrometers T he early bird cage and box-like quadrantelectrometers maintained the vane at aconstant potential while the potential/chargebeing measured was applied to one pair ofquadrants.

Dolezalek Electrometer.

T he Dolezalek electrometer, invented by theHungarian, Friedrich Dolezalek (1873 -1920), represented a significant improvementover earlier versions of quadrant electrometersby virtue of its increased sensitivity. It wasinvented in the same year that radioactivity wasdiscovered (1896) and it quickly became afavorite of those investigating radioactivesubstances (e.g., Ernest Rutherford). Dolezalekspent most of his career in Germany and hisresearch spanned a variety of fields: physics,chemistry, and electrical engineering.N ote that the quadrant electrometers of the 1800s did not provide

the sensitivity or the reliability that was required for radioactive work.


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In modern parlance, an electrometer is a highly sensitive electronicvoltmeter whose input impedance is so high that the current flowing into it can beconsidered, for practical purposes, to be zero. Among o ther applications, they areof use in nuclear physics as they are able to measure the tiny charges left in matterby the passage of ionizing radiation. The most common use for modernelectrometers is probably the measurement of radiation with ionization chambers,in instruments such as Geiger counters.

Source:

W ikipedia http://en.wikipedia.org/wiki/Electroscope Wikipedia http://en.wikipedia.org/wiki/Electrometer John Jenkins Spark M useum


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L aws G overning T he F rictionA fter a breath taking experiments in electrostaticsby many great scientist following his footstepsCharles-Augustin de Coulomb(14 June 1736 23 August 1806) was a French physicist. He is bestknown for developing Coulomb's law, thedefinition of the electrostatic force of attractionand repulsion.

E ighteenth-century experimenters dealt with electricity only in itsstatic form; they studied charges, not currents. They had long known thatopposite charges attract each other, while like charges repel, but the exact lawgoverning electrical forces remained unclear until the French engineer CharlesColoumb tackled the problem in 1785.In 1777 Coulomb invented the torsion balance,

also called torsion pendulum , and is a scientificapparatus for measuring very weak forces. Thetorsion balance was an insulating rod with ametal-coated ball attached to one end,suspended by a silk thread. The ball wascharged with a known charge of staticelectricity, and a second charged ball of thesame polarity was brought near it. The twocharged balls repelled one another, twisting thefibre through a certain angle, which could beread from a scale on the instrument. Byknowing how much force it took to twist thefibre through a given angle, Coulomb was ableto calculate the force between the balls. Determining the force for differentcharges and different separations between the balls, he showed that it followedinverse square law.


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Coulomb's 1779 memoir, The Theory of Simple Machines, is acompilation of his early experiments on statics and mechanics in which he makesthe first formal statement of the laws governing friction. In 1784 he studiedtensional elasticity, finding the relationship between the various factors involvedin the small oscillations of a body subjected to torsion.H is most notable papers are the seven which Coulomb presentedbefore the academy in 1785 and 1786. In the first he announced the measurementof the electrical forces of repulsion between electrical charges. He extended thiswork to the forces of attraction in his second memoir. This led to furtherquantitative work and his famous law of force for electrostatic charges (Coulomb'slaw). Coulomb explained the laws of attraction and repulsion between electriccharges and magnetic poles, although he did not find any relationship betweenthe two phenomena. He thought that the attraction and repulsion were due todifferent kinds of fluids.U sing a torsion balance, Coulomb was able to measure theelectrostatic force between two electrically charged objects of small dimensions.His observations led him to discover a mathematical relationship that came to becalled Coulomb's law. This law may be stated as follows: the magnitude of theelectrostatic force between two point charges is directly proportional to themagnitudes of each charge and inversely proportional to the square of thedistance between the charges. The formula to Coulomb's Law is of the same formas Newton's Gravitational Law: The electrical force of one body exerted on thesecond body is equal to the force exerted by the second body on the first. Tocalculate the magnitude of the force, it may be easiest to consider the simplified,scalar version of the law:

where:is the magnitude of the force exerted,is the charge on one body,is the charge on the other body,is the distance between them,

8.988109 N m 2 C -2 is the electrostatic constant orCoulomb force constant, and8.8541012 C2 N -1 m -2 is the permittivity of free space, also calledelectric constant, an important physical constant.


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Coloumbs experiments were open to criticism & are extremelydifficult to replica. The idea of an inverse-square law of electrical or magneticforces on the analogy of Newtonian gravity was not new, but Coloumb was thefirst to provide extensive experimental evidences. As a Newtonian he was moreconcerned with establishing the mathematical equations governing the actions ofelectrical forces than with discussing their cause. He used two fluid rather than aone fluid theory, but stated that this was simply because he found it moreconvenient. T he subsequent papers dealt with the loss of electricity of bodiesand the distribution of electricity on conductors. He introduced the "proof plane"and by using it was able to demonstrate the relationship between charge densityand the curvature of a conducting surface.T hese papers on electricity and magnetism, although the mostimportant of Coulomb's work over this period, were only a small part of thework he undertook. He presented twenty-five memoirs to the Academe desSciences between 1781 and 1806. Coulomb worked closely with Bossut, Borda, deProny, and Laplace over this period.

M easuremen t of surface density of electrification theory of the proof planeIn testing the results of the mathematical theory of thedistribution of electricity on the surface of theconductors, it is necessary to be able to measure thesurface-density at different points of conductor. For thispurpose Coloumb employed a small disk of gilt paperfastened to an insulating stem of gumlac. He applied thisdisk to various points of the conductor by placing it soas to coincide as nearly as possible with the surface ofthe conductor. He then removed it by means of theinsulating stem, & measured the charge of the disk by means of his electrometer.S ince the surface of the disk, when applied to the conductor, nearly

coincide with that of the conductor, he concluded that the surface-density of theconductor at that place, & that the charge on the disk when removed was nearlyequal to that on the area of the surface of the conductor equal to that on an areaof the disk. A disk, when employed in this way, is called a Coloumb's proof plane.


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T he experimen t to show charge resides on the surface of the conductor;Faradays BagF araday's bag is used to show that electric chargeresides on the surface of a conductor. The examplefrom Colby College above shows the original form: Amuslin bag is attached to a metal hoop supported byan insulating glass rod. An electric charge is placed onthe interior of the bag, and reappears on the outersurface of the bag. Its presence there can bedemonstrated with a proof plane and electroscope. Ifthe bag is then turned inside out by pulling on thestrings, the charge appears on the new outside of thebag. This is clearly a version of the Faraday Ice Pail experiment.Throughout his career, Coulomb espoused a characteristically eighteenth-

century view of nature according to which material corpuscles were boundtogether by short-range forces such as cohesion and elasticity. Much ofhis groundbreaking research into friction, torsion, and the strength of materialswere concerned with the limits of action of these forces. He was one of the chiefarchitects of the "two-fluid" theories of electricity and magnetism that dominatedthese fields throughout the nineteen th cen tury.L et us end with quoting the tribute paid to him by Biot who wrote:-

I t is to Borda and to Coulomb that one owes the renaissance of truephysics in France, not a verbose and hypothetical physics, but that ingenious andexact physics which observes and compa res all with rigour.Source:

Wikipedia http://en.wikipedia.org/wiki/Charles-Augustin_de_Coulomb A Treatise on Electricity and Magnetism By James Clerk Maxwell John Jenkins Spark M useum

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