Question

State and explain Lenz's law for induced e.m.f.

Answer 1

Lenz's 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 an current that's magnetic field opposes the change which produces it.
The negative sign used in Faraday's law of electromagnetic induction, indicates that the induced emf ($ϵ$) and the change in magnetic flux ( $\delta {\varphi }_B$ ) have opposite signs.
$ϵ-N\frac{d{\varphi }_B}{dt}$
B is the magnetic field, N is number of turns in coil.
Lenz's law obeys the law of conservation of energy and if the direction of the magnetic field that creates the current and the magnetic field of the current in a conductor are in same , then these two magnetic fields would add up and produce the current of twice the magnitude creating more magnetic field. This will cause more current and leads to violation of the law of conservation of energy.