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1、ElectroMagneticInductionWelearnedthatcurrentcarryingwiresproduceamagneticfieldaroundthem.Thereverseisalsotrue.Amovingmagnetcaninduceacurrentinawire.Thecurrentiscalledaninducedcurrentbecauseitcomesabout(isinduced)bythechangingmagneticfield.Chapter19:Magnetism
2、ElectroMagneticInductionIfweholdamagnetnearacoilofwirenothinghappens.Ifwenowmovethemagnettowardsorawayfromthecoil,avoltageandcurrentisinduced.Let’sseeifMr.Maloneycandoitacoupleways.Chapter19:MagnetismElectroMagneticInductionWhenthemagnetmovestowardsthecoilth
3、emagneticfieldthroughthecoilincreases,inducingacurrent.Whenitismovedaway,thefielddecreases,creatingacurrent,butintheoppositedirection.Chapter19:MagnetismInducedEMFandCurrentThechangingmagneticfieldcausesaninducedcurrent.Sinceasourceofemf(voltage)isneededtopr
4、oduceacurrent(rememberOhm’sLaw),themovingmagnetactslikeasourceofemf.Sowewouldsaythemovingmagnetinducesanemfinthecoil,producinganinducedcurrent.Chapter19:MagnetismMotionalEMFThemagnetdoesnothavetomove,buttheredoeshavetoberelativemotionbetweenthewirecircuitand
5、amagneticfield.Anotherwaytodothisistomoveaconductorinamagneticfield.Chapter19:MagnetismMotionalEMFWhenthebarmovesthroughthefield,aforceisappliedontheelectronsinit.Inthiscasetheforcepointsup.ThiscausesamagneticforcethatseparatesthechargesaccordingtoF=q⋅v⋅BCha
6、pter19:MagnetismMotionalEMFThemobileelectronsmovetothebottom,leavingapositivechargeatthetop.Thischargedifferencenowcreatesanattractiveelectricforcewhichcompetesagainstthemagneticforce.Theseparationstopswhentheelectricforcebalanceswiththemagneticforce.Derivew
7、hat’shappeningMr.Maloneytheclassroars.Chapter19:MagnetismMotionalEMFWecanseethatthemotionalemf[E]isdefinedasE=vBLWhereEistheemf,visthevelocity,Bisthemagneticfieldstrength,andListhelengthoftheconductorbar.Asyoucansee,E=0whenv=0,andasvincreases,sodoesE.Chapter
8、19:MagnetismMagneticFluxAnotherwaytodescribethismotionalemfisintermsofsomethingcalledmagneticflux.Magneticflux[Φ]issimilartotheluminousfluxorelectricflux.Itisdealswiththemagneticfieldandthesurfa
