There are two coils `A` and `B` as shown in Figure. 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

Options

A. there is a constant current in the clockwise direction in A
B. there is a varying current in A
C. there is no current in A
D. there is a constant current in the counter clockwise direction in A

Answer

D

Explanation

When A is moved towards B, current starts flowing in B. This is due to the variation of magnetic flux `(phi)`. When A stops moving, the current in B becomes zero. This is possible only if the current in A is constant. If the current in A is variable, there will be an induced current in B, even if A stops moving. (Option d)