Same as problem 4 except the coil A is made to rotate about a vertical axis figure. No current flows in B if A is at rest. The current in coil A, when the current in B (at t = 0) is counter clockwise and the coil A is as shown at this instant, t = 0, is

Options

A. constant current clockwise
B. varying current clockwise.
C. varying current counter clockwise.
D. constant current counter clockwise.

Answer

A

Explanation

When loop A is rotated, flux linked with loop B decreases and according to Lenz.s law induced current will oppose this decrement. Now, induced current in B is in counterclockwise (given) which indicates that outward flux linked with loop B decreases.
This is possible only when prevailing current in loop A must be in clockwise and it should be constant because when loop A is stationary no current is induced in loop B. (Consider loop A as magnet and think about how magnetic field lines of loop A link with loop B).