Question

Lenz’s law is in accordance with the law:
A) Conservation of charge
B) Conservation of flux
C) Conservation of momentum
D) Conservation of energy

Answer 1

Hint: Following points are important for the given problem:
(1) Explanation of Faraday’s law of EMI
(2) Direction of induced EMF in the circuit

Complete step by step solution:
According to Lenz's law if the magnetic flux associated with the loop changes, then the induced current is produced in the loop, such that the magnetic field due to the induced current opposes the change in the magnetic flux.
The direction of the magnetic field depends on the condition of the magnetic flux increasing or decreasing.
Remember:
(1) For counter clockwise current, EMF is positive.
(2) For clockwise current, EMF is negative.
Consider when the north pole of the magnet is brought near the force of the coil becomes the North pole according to Lenz’s law due to which the repulsive force acts between the magnet and the coil. Same work has to be done against the repulsive force in bringing the North pole of magnet towards the coil. This mechanical work is obtained in the form of electrical energy i.e. induced current (i) in the coil.


Similarly if the north pole is taken away from the coil, the face becomes the South pole and the attractive forces act between them. In this case the work done is against this attractive force, resulting electrical energy (current)


Thus it is clear that Lenz's law is based on the law of conservation of energy.

Note: For such type of problems, the detailed explanation of the following terms is necessary:
(1) Faraday’s law of EMI (experimentally)
(2) Law of conservation of energy
(3) Lenz’s law statement