1. LenzLawofElectromagneticInduction UnderBasicElectrical Lenz'slawisnamed aftertheGerman scientist H. F.E. Lenzin1834.Lenz'slaw obeysNewton'sthirdlawof motion(i.eto everyactionthere isalwaysanequaland oppositereaction)and the conservationofenergy (i.e energy may neither be created nor destroyedandthereforethesumofallthe energiesin the systemisa constant). Lenz law is based on Faraday's lawof induction, so before understanding Lenz's law; one should know what is Faraday’s law of induction? When a changing magnetic fieldis linked with a coil, an emfisinducedinit.Thischangeinmagnetic fieldmaybecausedby changing the magnetic fieldstrength by moving a magnet towards or away from the coil, or moving the coil into or out of the magnetic fieldas desired. Or in simple words, we can say that the magnitude oftheemfinducedinthecircuitisproportionaltotherateofchange offlux. Lenz'sLaw Lenz'slawstatesthatwhenanemfisgeneratedbyachangein magnetic fluxaccording to Faraday's Law, the polarity of the induced emf is such, that it produces an currentthat's magnetic fieldopposesthechangewhichproducesit. ThenegativesignusedinFaraday'slawofelectromagneticinduction,indicatesthat theinducedemf(ε )andthechange inmagneticflux(δΦB)haveopposite signs.

2. Whereε= InducedemfδΦB= change inmagnetic flux • N=Noofturns incoil • ReasonforOpposing,CauseofInducedCurrentinLenz'sLaw? • As stated above, Lenz's law obeys the law of conservation of energyandifthedirectionofthemagneticfieldthatcreatesthe • currentandthemagnetic fieldofthecurrentinaconductorarein samedirection,thenthesetwomagneticfieldswouldaddupand • produce the currentof twice the magnitude and this would in turn createmoremagneticfield,whichwillcausemorecurrentandthis • processcontinuingonandonleadstoviolationofthelawof conservationofenergy. • If the inducedcurrentcreates amagnetic fieldwhich is equal and opposite to the direction ofmagnetic fieldthat creates it, then only it can resist the change in the magneticfieldin thearea, whichisin accordancetothe Newton'sthirdlawof motion. • ExplanationofLenz'sLaw • ForunderstandingLenz'slaw,considertwocases:CASE-IWhena • magnetismovingtowardsthe coil. When the north pole of the magnet is approaching towards the coil, the magnetic flux linking to the coil increases. According to Faraday's law of electromagnetic induction, when there is change in flux, an emf and hence currentis induced in the coil and this currentwill create its own magnetic field. Now according to Lenz's law, this magnetic fieldcreatedwillopposeitsownorwecansayopposestheincreaseinfluxthrough

3. the coil and this is possible only if approaching coil side attains north polarity, as we know similar poles repel each other. Once we know the magnetic polarity of the coil side, we can easily determine the direction of the induced currentby applying right handrule.Inthiscase,thecurrentflowsinanticlockwisedirection. CASE-IIWhena magnetis movingawayfrom thecoil When the north pole of the magnet is moving away from the coil, the magnetic flux linking to the coil decreases. According to Faraday's law of electromagnetic induction, an emf and hence currentis induced in the coil and this currentwill create its own magnetic field. Now according to Lenz's law, this magnetic fieldcreated will oppose its own or we can say opposes the decrease in flux through the coil and this is possible only if approaching coil side attains south polarity, as we know dissimilar poles attract eachother. Onceweknowthemagneticpolarityofthecoilside,wecaneasily determinethedirectionoftheinducedcurrentbyapplyingrighthandrule.Inthis case, thecurrentflows in clockwise direction. NOTE:Forfindingthedirectionsofmagneticfieldor current, use right hand thumb rule i.e if the fingers of the right hand are placed around the wire so that the thumb pointsinthedirectionofcurrentflow,thenthecurlingof fingerswillshowthedirectionof produced by themagneticfield thewire.

4. TheLenzlawcan • besummarizedasunder: • If themagnetic fluxФ linking a coilincreases, the direction ofcurrentinthe coil will be such that it will oppose the increase in flux and hence the inducedcurrentwill produceitsfluxinadirectionasshownbelow(usingrighthandthumbrule). • IfmagneticfluxФlinkingacoilisdecreasing,theflux producedbythecurrentinthecoilissuch,thatitwillaidthemainfluxandhencethe • direction ofcurrentisasshownbelow, • ApplicationofLenz'sLaw • Lenz'slawcanbeusedtounderstandtheconceptofstored • magneticenergyinan inductor.Whenasourceof emfisconnected • acrossaninductor,acurrentstartsflowingthroughit.Thebackemf willopposethisincreaseincurrentthroughtheinductor.Inorderto

5. establish the flow of current, the external source of emf has to do someworktoovercomethisopposition.Thisworkcanbedoneby the emf is stored in the inductorand it can be recovered after removingtheexternalsource ofemffromthecircuit • This law indicates that the induced emf and the change in flux have opposite signs which provide a physical interpretation of the choice of sign inFaraday's law of induction. • Lenz's law is also applied to electric generators. When ancurrentis induced in a generator, the direction of this inducedcurrentis such that it opposes and causes rotation of generator (as in accordance to Lenz's law) and hence the generator requires more mechanicalenergy.Italso providesbackemf incase ofelectric motors. • Lenz’slaw is alsoused in electromagneticbrakingandinductioncooktops.