lecture 5 section 7
DESCRIPTION
TRANSCRIPT
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Chapter 5Chapter 5
Electricity and Electricity and MagnetismMagnetism
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OutlineOutline• ChargeCharge
DefiningchargeDefiningcharge Forcesoncharges:Coulomb’slawForcesoncharges:Coulomb’slaw
• ElectricityandmatterElectricityandmatter• CurrentCurrent
PotentialdifferencePotentialdifference Ohm’sLawOhm’sLaw ElectricpowerElectricpower
• MagnetismMagnetism MagneticforcesMagneticforces MagneticfieldMagneticfield TheconnectionbetweenelectricityandTheconnectionbetweenelectricityandmagneticfieldsmagneticfields
• ApplicationsApplications
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ChargeCharge
•WehavebeendiscussingabasicWehavebeendiscussingabasicpropertyofmattercalledmasspropertyofmattercalledmass
• Inelectricity,thebasicconceptiscalledInelectricity,thebasicconceptiscalledchargecharge
• Classicalmechanicsdoesn’texplainwhatClassicalmechanicsdoesn’texplainwhatmassis,justhowitbehaves:howitmassis,justhowitbehaves:howitmoves,etc.moves,etc.
• Similarly,classicalE&M(electricitySimilarly,classicalE&M(electricityandmagnetism)doesnottelluswhatandmagnetism)doesnottelluswhatchargeisexactly,onlyhowitbehaveschargeisexactly,onlyhowitbehaves
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Positive and Negative Positive and Negative ChargesCharges
•BenFranklin(1706-1790)namedBenFranklin(1706-1790)namedthetwokindsofcharges:Positivethetwokindsofcharges:PositiveandNegativeandNegative
•AllchargeiseitherpositiveorAllchargeiseitherpositiveornegativenegative
•LikechargesrepeleachotherLikechargesrepeleachother
oror•OppositechargesattracteachOppositechargesattracteachotherother
-- --++ ++
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Net ChargeNet Charge
• NetCharge:thetotalamountofNetCharge:thetotalamountofchargeonanobjectchargeonanobject Formostobjectsthenetcharge=zeroFormostobjectsthenetcharge=zero
• ““Charged”meansCharged”means Havingmoreofonekindofcharge(+Havingmoreofonekindofcharge(+or-)or-)
MovingaroundelectronsMovingaroundelectrons• Charges(i.e.,electrons)canbeCharges(i.e.,electrons)canbemovedaroundmovedaround ByfrictionByfriction ByinductionByinduction
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Friction and InductionFriction and Induction
• FrictionFriction ChargesfromoneChargesfromoneobjectareobjectaretransferredtotransferredtoanotheranother
• InductionInduction AchargedobjectAchargedobjectinducesachargeinducesachargeseparationinaseparationinasecondobjectsecondobject
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Conservation of ChargeConservation of Charge
• ThenetchargeinanisolatedsystemThenetchargeinanisolatedsystemcannotchangecannotchange ThismeansthatthesumofthenegativeThismeansthatthesumofthenegativeandpositivechargesinanysystemandpositivechargesinanysystemremainsconstantremainsconstant
• Onecanmovechargesaround,butOnecanmovechargesaround,butcannotcreateordestroychargecannotcreateordestroycharge
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Defining ChargeDefining Charge
• AllmatteriscomposedofatomsAllmatteriscomposedofatoms
• AllatomsarecomposedofthreeAllatomsarecomposedofthreeelementaryparticleselementaryparticles Protons(mass=1.673x10Protons(mass=1.673x10-27-27kg,kg,charge=1.06x10charge=1.06x10-19-19Coulombs)Coulombs)
Electrons(mass=9.11x10Electrons(mass=9.11x10-31-31kg,kg,charge=-1.06x10charge=-1.06x10-19-19Coulombs)Coulombs)
NeutronNeutrons s (mass=1.675x10(mass=1.675x10-27-27kg,kg,charge=0charge=0Coulombs)Coulombs)
• 1Coulomb=6.25×101Coulomb=6.25×101818electronselectrons
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Coulomb’s LawCoulomb’s Law
• ForcebetweentwopointForcebetweentwopointchargescharges TheforceexertedbyonechargedTheforceexertedbyonechargedobjectonanotherchargedobjectisobjectonanotherchargedobjectisproportionaltothechargeofeachproportionaltothechargeofeachobjectandtotheinverseoftheobjectandtotheinverseofthe(distance)(distance)22betweentheobjectsbetweentheobjects
theforcecanbetheforcecanbe Attractive-oppositelychargedobjectsAttractive-oppositelychargedobjects Repulsive-similarlychargesobjectsRepulsive-similarlychargesobjects
““k”iscalled“coulomb’sconstant”,k”iscalled“coulomb’sconstant”,(k=9x10(k=9x1099NmNm22/C/C22))
€
F=kq1 × q2
r2
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Another Inverse Square Another Inverse Square LawLaw
• RememberwehavealreadyseentheRememberwehavealreadyseentheinversesquaredistancedependenceinversesquaredistancedependenceintheuniversallawofgravityintheuniversallawofgravity
• Inmanyways,theforceofInmanyways,theforceofelectrostaticinteractionisveryelectrostaticinteractionisverysimilartotheforceofgravitationalsimilartotheforceofgravitationalinteraction,buttherearesomeinteraction,buttherearesomemajordifferencesmajordifferences
€
Fe =kq1 × q2
r2
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Electrostatic Electrostatic InteractionsInteractions
• TheforceduetoelectrostaticinteractionisTheforceduetoelectrostaticinteractionismuchlargerthantheforceduetogravitymuchlargerthantheforceduetogravity TheratiooftheelectricandgravitationalTheratiooftheelectricandgravitationalforcesbetweentheelectronandprotoninaforcesbetweentheelectronandprotoninahydrogenatomisFhydrogenatomisFelecelec/F/Fgravgrav=2.2×10=2.2×103939
• Sowhydon’twenoticeelectricalforcesSowhydon’twenoticeelectricalforcesmore?more? MassescannotcanceleachotherwhileMassescannotcanceleachotherwhilechargescan(1g+1g=2g,1C+-1C=0C)chargescan(1g+1g=2g,1C+-1C=0C)
• TheforceduetogravitycanonlybeTheforceduetogravitycanonlybeattractiveattractive
• ElectrostaticforcescanberepulsiveorElectrostaticforcescanberepulsiveorattractiveattractive
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Material MattersMaterial Matters
• Forsomematerials,onceanimbalanceForsomematerials,onceanimbalanceofchargeisproduced,thecharge“sticksofchargeisproduced,thecharge“sticksaround”around” ThesematerialsarecalledelectricalThesematerialsarecalledelectricalinsulatorsinsulators
• Forothermaterials,thechargeForothermaterials,thechargeimbalanceisverydifficulttoachieve---itimbalanceisverydifficulttoachieve---itseemsasthoughtthechargejustpassesseemsasthoughtthechargejustpassesthroughthematerial(e.g.metals)throughthematerial(e.g.metals) ThesematerialsarecalledelectricalThesematerialsarecalledelectricalconductorsconductors
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Levels of ConductivityLevels of Conductivity
• ConductorConductor MaterialthroughwhichelectronscaneasilyMaterialthroughwhichelectronscaneasilymovemove
• InsulatorInsulator MaterialinwhichelectronsremainfixedinMaterialinwhichelectronsremainfixedinonelocationundernormalcircumstancesonelocationundernormalcircumstances
• ButnotallmaterialscanbedistinctlyButnotallmaterialscanbedistinctlycharacterizedbythesesimpledefinitionscharacterizedbythesesimpledefinitions Semiconductors–HaveconductivitybetweenSemiconductors–Haveconductivitybetweenconductorandinsulator-usedintransistorsconductorandinsulator-usedintransistors
Superconductors–ElectronsflowthroughSuperconductors–Electronsflowthroughthesematerialswithnoresistancethesematerialswithnoresistance
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IonsIons• TheconductionofelectricitythroughliquidsTheconductionofelectricitythroughliquidsandgasesinvolvesthemovementofionsandgasesinvolvesthemovementofions
• Wheneveranatomgainsorlosesanelectron,Wheneveranatomgainsorlosesanelectron,wesaythattheatomisionizedwesaythattheatomisionized
• AnionissimplyanatomwithexcesschargeAnionissimplyanatomwithexcesscharge TheioncanbepositiveornegativeTheioncanbepositiveornegative
• IonizationcanbeaccomplishedinseveralIonizationcanbeaccomplishedinseveralwaysways SparksSparks FlameFlame UVandX-raysUVandX-rays
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Electric PotentialElectric Potential
• WheneverapotentialdifferenceWheneverapotentialdifferenceexists,anychargewillmovetotheexists,anychargewillmovetothepositionwiththelowestpotentialpositionwiththelowestpotential
• DifferencesinpotentialarecausedDifferencesinpotentialarecausedbydifferencesinthenetvalueofbydifferencesinthenetvalueofelectricfieldthatvariesfrompointelectricfieldthatvariesfrompointtopointinspacetopointinspace
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Electric PotentialElectric Potential
• Unit:VoltUnit:Volt=Joule/=Joule/CoulombCoulomb
=kgm=kgm22/s/s22CC€
Electric Potential =
Potential Energy
Charge
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Voltage of BatteriesVoltage of Batteries• Justaseveryliterofwatercando8timesmoreJustaseveryliterofwatercando8timesmoreworkifdroppedfrom8timesashigh,everyworkifdroppedfrom8timesashigh,everyCoulombdoes8timesmoreworkifthevoltageis8Coulombdoes8timesmoreworkifthevoltageis8timesasgreattimesasgreat
• The12Vbatterywillpush8timesmoreelectronsThe12Vbatterywillpush8timesmoreelectronsthroughthesamecircuitinagiventime.throughthesamecircuitinagiventime.
12m12m
1.5m1.5m
12V12V
1.5V1.5V
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Electric CurrentElectric Current
• WhenchargeflowsfromoneplacetoWhenchargeflowsfromoneplacetoanother,anelectriccurrentisformedanother,anelectriccurrentisformed
• MostpracticalapplicationsofelectricalMostpracticalapplicationsofelectricalphenomenaarebasedonthephenomenaarebasedontheunderstandingofelectriccurrentunderstandingofelectriccurrent
• Unitofcurrent:Ampere=CoulombperUnitofcurrent:Ampere=Coulombpersecondsecond
• Somerulesfortheflowofcharge:Somerulesfortheflowofcharge: CurrentcanonlyexistbetweentwopointsofCurrentcanonlyexistbetweentwopointsofdifferentpotentialconnectedbyaconductordifferentpotentialconnectedbyaconductor
CurrentcanonlyexistwheneveraconductiveCurrentcanonlyexistwheneveraconductivepathwithnobreaksisprovidedpathwithnobreaksisprovided
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AC/DCAC/DC
• AC:AlternatingCurrent(wallAC:AlternatingCurrent(wallsocket)socket)
• DC:DirectCurrent(battery)DC:DirectCurrent(battery)
• What’sthedifference?What’sthedifference? AC:AC:timedependentvoltagetimedependentvoltage
DC:DC:constantvoltageconstantvoltage
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Current: “Flowing” Current: “Flowing” ChargeCharge
• FlowofchargeissimilartoflowingwaterFlowofchargeissimilartoflowingwater
Ifthefaucetisclosed,theflowstopsIfthefaucetisclosed,theflowstops Ifthepumpisturnedoff,theflowstopsIfthepumpisturnedoff,theflowstops
PUMPPUMP
FAUCETFAUCETHOSE OR FILTERHOSE OR FILTER
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Electric Circuit ElementsElectric Circuit Elements
• Battery:sourceofpotentialdifferenceBattery:sourceofpotentialdifference
• Resistor:theresistanceinanelectricResistor:theresistanceinanelectriccircuitisameasureofhow“difficult”circuitisameasureofhow“difficult”isistomovechargethroughthecircuitisistomovechargethroughthecircuit
SWITCHSWITCH(like the faucet)(like the faucet)
RESISTORRESISTOR(like crimps in the hose)(like crimps in the hose)
BATTERYBATTERY(like the pump)(like the pump)
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Ohm’s LawOhm’s Law
• ThereisarelationshipbetweentheThereisarelationshipbetweenthecurrent,voltage,andresistanceincurrent,voltage,andresistanceinanelectriccircuitanelectriccircuit
• TheseparametersareusuallyTheseparametersareusuallyrepresentedbytheletters:representedbytheletters: IcurrentIcurrent VvoltageVvoltage Rresistance(unit=ohm,symbol=Rresistance(unit=ohm,symbol=))
• TheyarerelatedbyOhm’slaw:TheyarerelatedbyOhm’slaw: V=I×RV=I×R
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Electric ShockElectric Shock
• ElectricshockisgovernedbyOhm’slawElectricshockisgovernedbyOhm’slaw LoweredresistancemeanshighercurrentLoweredresistancemeanshighercurrent Highcurrentisdeadly!Highcurrentisdeadly!
• A“highvoltage”doesnotdirectlyharmyouA“highvoltage”doesnotdirectlyharmyou
• CurrentiswhatpassesthroughobjectsCurrentiswhatpassesthroughobjectswhenchargesflowtowardalowerpotentialwhenchargesflowtowardalowerpotential
• AccordingtoOhm’slaw:AccordingtoOhm’slaw: LowresistancewithhighvoltagemeanslargeLowresistancewithhighvoltagemeanslargecurrentcurrent
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Electric ShockElectric Shock• TypicalResistanceoftheHumanSkinTypicalResistanceoftheHumanSkin
Dry:asmuchas500,000Ohms(500k)Dry:asmuchas500,000Ohms(500k) Wet:aslittleas100Ohms(ifwetwithsaltWet:aslittleas100Ohms(ifwetwithsaltwater)water)
• CurrentsinthehumanbodyCurrentsinthehumanbody
0.001Amp-youfeelit0.001Amp-youfeelit0.005Amp-youfeelpain0.005Amp-youfeelpain0.010Amp-musclespasmwiththe0.010Amp-musclespasmwiththe
painpain0.015Amp-lossofmusclecontrol0.015Amp-lossofmusclecontrol0.070Amp-seriousinjury0.070Amp-seriousinjury
• Acurrentofonly0.070(or70milli-Amps)Acurrentofonly0.070(or70milli-Amps)passingthroughtheheartmuscleformorepassingthroughtheheartmuscleformorethanonesecondcancausethehearttostopthanonesecondcancausethehearttostopbeatingbeating
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Electric ShockElectric Shock
• Ifyourskinisdry,thenR500,000Ifyourskinisdry,thenR500,000
• SinceV=120VformostoutletsinSinceV=120VformostoutletsintheUS,Ohm’sLawpredicts:theUS,Ohm’sLawpredicts:
I=V/R=120V500,000I=V/R=120V500,000
=0.0002Amps=0.0002Amps
Painful,butnotdeadlyPainful,butnotdeadly
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Electric ShockElectric Shock
• Ifyourskiniswet,thenRcanbeaslowIfyourskiniswet,thenRcanbeaslowasas1,0001,000
• SoforaV=120Voutlet,wehave:SoforaV=120Voutlet,wehave:
I=V/R=120V1,000I=V/R=120V1,000
=0.12Amps=0.12Amps
WhichcanbefatalifthecurrentWhichcanbefatalifthecurrentpassesthroughtheheartpassesthroughtheheart
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Electric PowerElectric Power• TheflowofcurrentisthesourceofTheflowofcurrentisthesourceofelectricenergyelectricenergy Wheneveracurrentflows,someenergyWheneveracurrentflows,someenergyisbeingtransformedintoheatisbeingtransformedintoheat
TheremainderoftheenergycanbeTheremainderoftheenergycanbeusedtodoworkusedtodowork
• TherateatwhichelectriccurrentisTherateatwhichelectriccurrentisdoingworkiscalledelectricpowerdoingworkiscalledelectricpower
• ElectricpowerisproportionaltoElectricpowerisproportionaltoboththecurrentandthepotentialboththecurrentandthepotentialdifference:difference:
€
Power = Current × Voltage = IV
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Electric CircuitsElectric Circuits
• TheamountofcurrentflowingthroughTheamountofcurrentflowingthroughthecircuitpathsandtheeffectivethecircuitpathsandtheeffectiveresistanceofthecircuitdependsuponresistanceofthecircuitdependsuponhowthecircuitelementsarearrangedhowthecircuitelementsarearranged
• MostcircuitsarearrangedintwoMostcircuitsarearrangedintwobasicways:basicways: Series(voltagesplitamongelements)Series(voltagesplitamongelements) Parallel(currentsplitamongelements)Parallel(currentsplitamongelements)
• TheamountofcurrentthatcanflowinTheamountofcurrentthatcanflowinacircuitdependsonthearrangementacircuitdependsonthearrangementoftheresistancesinthecircuitoftheresistancesinthecircuit
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Series CircuitsSeries Circuits
• Series(voltagesplitSeries(voltagesplitamongelements)amongelements)
• ResistanceisResistanceishigherthanforahigherthanforasinglebulb,sosinglebulb,socurrentthroughthecurrentthroughthecircuitisreducedcircuitisreduced
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Parallel CircuitsParallel Circuits
• CurrentsplitCurrentsplitamongelementsamongelements
• BecausetheBecausetheelementsinaelementsinaparallelcircuithaveparallelcircuithavethesamevoltagethesamevoltageacrossthem,theacrossthem,thecurrentthroughcurrentthrougheachbulbisgreatereachbulbisgreaterthanintheseriesthanintheseriescasecase
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MagnetismMagnetism
• Atonepoint,electricityandAtonepoint,electricityandmagnetismwereunderstoodtobemagnetismwereunderstoodtobecompletelyseparateinnaturecompletelyseparateinnature
• ScientistsdiscoveredinthenineteenthScientistsdiscoveredinthenineteenthcenturythatelectricalandmagneticcenturythatelectricalandmagneticphenomenaareactuallycloselyrelatedphenomenaareactuallycloselyrelated
• Allmagnetshavetwopoles,Allmagnetshavetwopoles,northandsouthnorthandsouth LikepolesrepelLikepolesrepel OppositepolesattractOppositepolesattract
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Electric and Magnetic Electric and Magnetic ForcesForces
• BothelectricandmagneticforcescanBothelectricandmagneticforcescanhaveaneffectonobjectswithoutbeinginhaveaneffectonobjectswithoutbeingindirectcontactwiththeobjects(Similartodirectcontactwiththeobjects(Similartotheeffectofgravity)theeffectofgravity)
• Weexplainthisabilitytodowork‘ataWeexplainthisabilitytodowork‘atadistance’withtheconceptof“forcefields”distance’withtheconceptof“forcefields”
• AnythingwithmassfillsallspacewithaAnythingwithmassfillsallspacewithagravitationalfieldgravitationalfield ItisthefieldthatcausestheforcesonanyItisthefieldthatcausestheforcesonanymassthatliesinthefieldmassthatliesinthefield
• Similarly,everychargedparticlefillsallSimilarly,everychargedparticlefillsallspacewithanelectricfieldspacewithanelectricfield WheneveranotherchargeliesintheelectricWheneveranotherchargeliesintheelectricfield,electricforcesactonitfield,electricforcesactonit
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The Connection between The Connection between Electricity and Electricity and
MagnetismMagnetism• OerstedshowedthatOerstedshowedthatelectricityandmagnetismelectricityandmagnetismwereinseparablephenomenawereinseparablephenomena
• HeshowedthatacompassHeshowedthatacompasscouldbeusedtodetectthecouldbeusedtodetectthepresenceofamagneticfieldpresenceofamagneticfield
• OerstedheldacompassnearOerstedheldacompassnearawirethroughwhichheawirethroughwhichhepassedacurrent,andfoundpassedacurrent,andfoundthatthecompassneedlewasthatthecompassneedlewasdeflectedbythecurrentinthedeflectedbythecurrentinthewirewire
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Direction of the Direction of the Magnetic FieldMagnetic Field
• Asimplerule,calledtherighthandAsimplerule,calledtherighthandruledeterminesthedirectionoftheruledeterminesthedirectionofthemagneticfieldproducedbyawiremagneticfieldproducedbyawire
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The Current Loop The Current Loop Magnet Magnet
• SoonscientistsunderstoodthatSoonscientistsunderstoodthatcurrentloopcouldbeconsideredascurrentloopcouldbeconsideredasasimplemagnetasimplemagnet
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Major Discovery - Major Discovery - InductionInduction
• AllmovingelectricAllmovingelectricchargesproducechargesproducemagneticfieldsmagneticfields
• ImportantImportantApplication:Application: ByusingacoilofByusingacoilofwireandhighwireandhighcurrent,strongcurrent,strongmagneticfieldcanmagneticfieldcanbeproduced.Thisbeproduced.Thisiscalledaniscalledanelectromagnetelectromagnet
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MagnetismMagnetism• AllmagneticphenomenaisAllmagneticphenomenaisproducedbymovingchargesproducedbymovingcharges
• CurrentsaremovingchargesCurrentsaremovingcharges SoamagnetexertsforceonaSoamagnetexertsforceonacurrent-carryingwirecurrent-carryingwire
AndthecurrentcarryingwireAndthecurrentcarryingwireproducesamagneticfieldproducesamagneticfield
• Insidematerials(e.g.–Insidematerials(e.g.–permanentmagnets)permanentmagnets) ThemovingchargeisintheformofThemovingchargeisintheformofelectronsspinningaroundnucleuselectronsspinningaroundnucleus
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The Electric MotorThe Electric Motor
• MakesuseoftheforceonacurrentMakesuseoftheforceonacurrentcarryingwirebyamagneticfieldcarryingwirebyamagneticfield
• Importantcomponent:CommutatorImportantcomponent:Commutator
ThecommutatorThecommutatorchangesthedirectionchangesthedirectionofthecurrentintheofthecurrentintheloopsothattheforceloopsothattheforcecontinuestopushincontinuestopushinthesamedirectionthesamedirection
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GeneratorsGenerators
• Thebasicidea:wheneverthereisrelativeThebasicidea:wheneverthereisrelativemotionbetweenawireloopandamagneticmotionbetweenawireloopandamagneticfield,acurrentisproducedfield,acurrentisproduced
• ThisiscalledinducedcurrentThisiscalledinducedcurrent
• Whenthedirectionofthecurrentischanged,Whenthedirectionofthecurrentischanged,thecurrentiscalledanalternatingcurrentthecurrentiscalledanalternatingcurrent
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TransformersTransformers
• TheideaofinducedcurrentledtotheTheideaofinducedcurrentledtothedevelopmentoftransformersdevelopmentoftransformers WhencurrentisalternatinginaloopofwireWhencurrentisalternatinginaloopofwire(calledtheprimaryloop),asecondarycurrent(calledtheprimaryloop),asecondarycurrentcanbeinducedinanearbyloopofwire(thecanbeinducedinanearbyloopofwire(thesecondaryloop)secondaryloop)
• Transformersareveryuseful,sincetheTransformersareveryuseful,sincethevoltageofthesecondaryinducedcurrentvoltageofthesecondaryinducedcurrentcanbecontrolledbythenumberofturnscanbecontrolledbythenumberofturns ThisisthewayelectricThisisthewayelectricenergy(atabout120Volts)energy(atabout120Volts)isdeliveredtoyourhomeisdeliveredtoyourhomefromhighvoltagepowerlinesfromhighvoltagepowerlines
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Transformer MathTransformer Math
• TherelationshipbetweenthevoltagesinTherelationshipbetweenthevoltagesintheloopsofatransformerisgivenbytheloopsofatransformerisgivenby
• LargetransformerscandecreasetheLargetransformerscandecreasethevoltagebyseveralthousandtimesvoltagebyseveralthousandtimes
1 1 2
2 2 1
primary turns primary voltage secondary current
secondary turns secondary voltage primary current
N V I
N V I
or for any two nearby loops
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Applications of Applications of MagnetismMagnetism
•MagneticRecordingMagneticRecording VideotapesVideotapes AudiotapesAudiotapes ComputerharddrivesComputerharddrives
• CRTTelevisionscreensCRTTelevisionscreens UsemagnetstodirecttheelectronsthatUsemagnetstodirecttheelectronsthatprovidethesourceofenergythatmakestheprovidethesourceofenergythatmakesthelightyouviewlightyouview
• NavigationNavigation Compasses–manmadeandbiological!Compasses–manmadeandbiological!
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The CompassThe Compass
• TheearthisagiantmagnetTheearthisagiantmagnet
• UsefulfornavigationUsefulfornavigation CompassesCompasses BirdsBirds BacteriaBacteria Cows!Cows! Humans?Humans?
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Application of Application of ElectrostaticsElectrostatics
1.1. ChargingCharging ThesurfaceofacylindricaldrumThesurfaceofacylindricaldrum
iselectrostaticallychargediselectrostaticallycharged2.2. ExposureExposure
Documentisilluminated,brightDocumentisilluminated,brightareasreflectlightwhichcreateareasreflectlightwhichcreatechargeconduitsinthechargeconduitsinthephotoconductorphotoconductor
3.3. DevelopingDeveloping PositivelychargedtonerstickstoPositivelychargedtonersticksto
negativelychargedareasnegativelychargedareas4.4. TransferTransfer
ThetoneronthedrumisThetoneronthedrumistransferredtoapieceofpapertransferredtoapieceofpaperwithahighernegativechargewithahighernegativecharge
5.5. FusingFusing TonerismeltedandbondedtotheTonerismeltedandbondedtothe
paperpaper6.6. CleaningCleaning
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E&M SummaryE&M Summary
• ChargeisafundamentalpropertyofChargeisafundamentalpropertyofelementaryparticleselementaryparticles Twotypes:negativeandpositiveTwotypes:negativeandpositive Unit:Coulomb(C)Unit:Coulomb(C) Fundamentalcharge:1.06Fundamentalcharge:1.06 1010-19-19C,called“C,called“ee””
• Atomsarecomposedofelectrons,protonsAtomsarecomposedofelectrons,protonsandneutronsandneutrons ElectronshaveElectronshave–e–e,protonshave,protonshave+e, neutrons +e, neutrons
are neutralare neutral AnatomwithadeficitofelectronsisapositiveAnatomwithadeficitofelectronsisapositiveionion
• CurrentistheflowofchargeCurrentistheflowofcharge Chargeflowsthroughaconductor,notChargeflowsthroughaconductor,notthroughaninsulatorthroughaninsulator
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E&M SummaryE&M Summary• VoltageisthetermgiventothepotentialVoltageisthetermgiventothepotentialdifferencebetweentwopointsdifferencebetweentwopoints VoltageUnit:Volt(V)VoltageUnit:Volt(V)
• Relationshipbetweencurrentandvoltage:Relationshipbetweencurrentandvoltage:Ohm’sLaw:Ohm’sLaw:
V=IRV=IR (Risresistance)(Risresistance)• Power:rateofdoingwork;P=IVPower:rateofdoingwork;P=IV• PermanentmagnetswhenthemagneticPermanentmagnetswhenthemagneticfieldcanbelinedupfieldcanbelinedup
• ElectromagneticinductionElectromagneticinduction CurrentproducedwhenthereisrelativemotionCurrentproducedwhenthereisrelativemotionbetweenacurrentloopandamagneticfieldbetweenacurrentloopandamagneticfield
BasisforthetransformerBasisforthetransformer