Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh,...

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Homework due Wednesday night 11:59 PM Exam 2: Sunday April 9, 6:10-7:10 PM, on Busch pracHce problems posted on web site start making your formula sheet now! BEFORE CLASS: Play with magnets and moving charged parHcles Lecture slides posted on main class web site CONGRATS ON 3/3 to Alnadi, Balance, Alison Bansil, Buznitsky, Dias, Dormer, Z. Feng, Huang, Johnson, Kanagala, Kershaw, McKeown, Motyala, Ning, Parikh, Ravichandran, Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao

Transcript of Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh,...

Page 1: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

HomeworkdueWednesdaynight11:59PMExam2:SundayApril9,6:10-7:10PM,onBuschpracHceproblemspostedonwebsitestartmakingyourformulasheetnow!BEFORECLASS:PlaywithmagnetsandmovingchargedparHclesLectureslidespostedonmainclasswebsite

CONGRATSON3/3toAlnadi,Balance,AlisonBansil,Buznitsky,Dias,Dormer,Z.Feng,Huang,Johnson,Kanagala,Kershaw,McKeown,Motyala,Ning,Parikh,Ravichandran,Rivera,Rondel,Scot,Smith,Suresh,Thuel,Tournoux,Yao

Page 2: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

Chapter 28 Magnetic Field and Forces, part 2

2 Phys 272

Page 3: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

LodestoneandbarmagnetsexertforceonmovingchargedparHclesbycreaHngamagne&cfieldBarmagnetfield:(nearends)ForcedependsonqandandonthemagneHcfield

B(r)

NS

!v B(r)

Page 4: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

ThemagneHcforceonachargedparHcleatCrossproductoftwovectorsDirec&on:PerpendiculartodirecHonofPerpendiculartodirecHonof->normaltotheplanedefinedbyandTwochoices–useright-handruletochooseThumbalongv;fingersalongB:outofpalm

!F = q"v ×

!B

q

!r

!v!v

!v

!B !

B

!B

Page 5: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

ThemagneHcforceonachargedparHcleatCrossproductoftwovectorsIfthevelocityandmagneHcfieldvectorsaregivenincomponentform,computebyexpandingthetermsExample:

!F = q"v ×

!B

!r

!v = vxi!B = Bxi + By j!v ×!B = vxi × (Bxi + By j) = vxBx (i × i )+ vxBy (i × j)

= vxByk

Page 6: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

i-clicker:AparHcleofcharge+1.0Cwithvelocity(inm/s)movesthroughtheuniformmagneHcfield(inT)WhatisthemagnitudeofthemagneHcforceontheparHcle?a)  12Nb)  6.0Nc)  4.5Nd)  1.5Ne) Noneoftheabove

6Phys272

!v = 2i +3 j!B = 3i −1.5 j

Page 7: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

i-clicker:AparHcleofcharge+1.0Cwithvelocity(inm/s)movesthroughtheuniformmagneHcfield(inT)WhatisthemagnitudeofthemagneHcforceontheparHcle?a)  12Nb)  6.0Nc)  4.5Nd)  1.5Ne) Noneoftheabove

7Phys272

!v = 2i +3 j!B = 3i −1.5 j

Page 8: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

MoHonofachargedparHcleqinauniformfieldBv0perpendiculartothefieldIniHallyF=qv0Bdownward

Boutofthescreen

Page 9: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

MoHonofachargedparHcleqinauniformfieldBv0perpendiculartothefieldIniHallyF=qv0BdownwardVelocitystaysconstant:magneHcforcedoesnoworkFstaysqv0Bperpendiculartovelocity

Boutofthescreen

Page 10: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

MoHonofachargedparHcleqinauniformfieldBv0perpendiculartothefieldIniHallyF=qv0BdownwardVelocitystaysconstant:magneHcforcedoesnoworkFstaysqv0Bperpendiculartovelocity

Boutofthescreen

Page 11: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

MoHonofachargedparHcleqinauniformfieldBv0perpendiculartothefieldUniformcircularmoHonTogettheradiusofthecircle,setthemagneHcforceequaltothecentripetalforceqv0B=mv02/rsor=mv0/qB

Boutofthescreen

Page 12: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

Typicalproblem:x=2mv0/(qB)Bintothescreen:posbendslek,negbendsright

Page 13: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

MoHonofachargedparHcleqinauniformfieldBv0xperpendiculartothefieldv0zparalleltothefield

Boutofthescreen

helixElectronbeamdemo

Page 14: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

ForceonacurrentcarryingwireinauniformmagneHcfieldBpointsoutofthescreenMagneHcforceistotherightForceonthechargesistransmiledtothewire

Electronsarethefreechargeshere

isinthedirecHonofthecurrent!L

Page 15: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

TorquealongtherotaHonaxis=Ftr(posiHve)

Page 16: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

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i-clicker:WhatisthesignofthetorqueontherectangularlooprotaHngonthefixedaxiswithauniformBfieldpoinHngtotheright?a)  PosiHve(upalongaxis)b)  NegaHve(downalongaxis)c)  Zerod)  Justguessing

!B

ii

Page 17: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

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i-clicker:WhatisthesignofthetorqueontherectangularlooprotaHngonthefixedaxiswithauniformBfieldpoinHngtotheright?a)  PosiHve(upalongaxis)b)  NegaHve(downalongaxis)c)  Zerod)  Justguessing

Torque=2(iBa)(b/2)=iB(ab)=iBarea

!B

ii

Page 18: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

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Page 19: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

Chapter 29 Currents Produce Magnetic Fields

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Page 20: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

Calculating the Magnetic Field due to a Current: Biot-Savart Law

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!B = d

!B∫

Page 21: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

Magnetic Field due to a Long Straight Wire

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Page 22: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

29.2: Magnetic Field due to a Long Straight Wire:

DEMO:needleandwireDEMO:ironfilingsontransparency

Page 23: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

Magnetic Field due to a Long Straight Wire

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Page 24: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

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i-clicker:Whereonthex-axis(excludinginfinity)isBtot=0?a)  Atapointx<0b) Atapointxsuchthat0<x<dc)  Atapointx>dd) Onlyatinfinity

Page 25: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

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i-clicker:Whereonthex-axis(excludinginfinity)isBtot=0?a)  Atapointx<0b) Atapointxsuchthat0<x<dc)  Atapointx>dd) Onlyatinfinity

Page 26: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

⊗ ⊗a b

i-clicker:

Atpointsonwireb,whatdirecHondoesthemagneHcfieldduetocurrentiain“wirea”point?a)Totherightb)Tothelekc)Upd)Downe)it’szero

Page 27: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

⊗ ⊗a b

i-clicker:

Atpointsonwireb,whatdirecHondoesthemagneHcfieldduetocurrentiain“wirea”point?a)Totherightb)Tothelekc)Upd)Downe)it’szero

Page 28: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

⊗ ⊗a b

i-clicker:

WhatisthedirecHonofthemagneHcforceonwirebduetothecurrentinwirea?a)Totherightb)Tothelekc)Upd)Downe)it’szeroDEMO

!B

Page 29: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

⊗ ⊗a b

i-clicker:

WhatisthedirecHonofthemagneHcforceonwirebduetothecurrentinwirea?a)Totherightb)Tothelekc)Upd)Downe)it’szeroDEMO

!B

Page 30: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

Force Between Two Parallel Wires

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Page 31: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

Magnetic Field due to a Current in a Circular Arc of Wire:

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B = dB = µ0iR2∫ ds =∫ µ0i

R2Rφ

Page 32: Homework due Wednesday night 11:59 PM Exam 2: Sunday … · Rivera, Rondel, Scot, Smith, Suresh, Thuel, Tournoux, Yao Chapter 28 Magnetic Field and Forces, part 2 ... moves through

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Ex: