Monday, 13 October 2014

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LEN'Z LAW



Lenz's law is named after the German scientist H. F. E. Lenz in 1834.   Lenz's law  obeys Newton's third law of motion (i.e to every action there is always an equal and opposite reaction) and the conservation of energy (i.e energy may neither be created nor destroyed and therefore the sum of all the energies in the system is a constant)
Lenz law is based on   Faraday's law   of induction so before understanding Lenz's law one should know what   Faraday’s law of induction   is. When a changing magnetic field is linked with a coil, an emf is induced in it. This change in magnetic field may be caused by changing the magnetic field strength by moving a magnet toward or away from the coil or moving the coil into or out of the magnetic field as desired. Or in simple words we can say that the magnitude of the emf induced in the circuit is proportional to the rate of change of flux

Lenz law states that when an emf is generated by a change in magnetic flux according to Faraday's Law, the polarity of the induced emf is such that it produces a current whose magnetic field opposes the change which produces it.


The negative sign is used in   Faraday's law of electromagnetic induction, indicates that the induced emf ( ε ) and the change in magnetic flux ( δΦ B   ) have opposite signs.

Where
ε = Induced emf
δΦ B   = change in magnetic flux
N = No of turns in coil

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