There are two coils A and B as shown in Fig 6.2. A current starts flowing in B as shown, when A is moved towards B and stops when A stops moving. The current in A is counterclockwise. B is kept stationary when A moves. We can infer that

Concept:

Lenz Law: It states that the direction of the induced current in a conductor by a changing magnetic field is such that the magnetic field created by the induced current opposes changes in the initial magnetic field.

\(\epsilon=-{d\phi\over dt}\)

Solution:

When coil A moves towards B, a current is induced in B counterclockwise direction. The current in B will stop when A stops moving.

→There cannot be a current in A clockwise direction as in B there is an anticlockwise field.

→Varying current in A will suggest a field in B even in the absence of movement in A which is also not possible.

The correct answer is option (4).