Same as problem `4` except the coil `A` is made to rotate about a vertical axis in the plane of the coil (Figure). No currents flows in `B` if `A` is at rest. The current in coil `A`, when the current in `B` (at `t = 0`) is counterclockwise 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 the current in B (at t = 0) is counter-clockwise and the coil A is considered above to it. The counter-clockwise flow of the current in B is equivalent to north pole of magnet and magnetic field lines are emanating upwards to coil A. When coil A start rotating at t = 0, then the current in A is constant along clockwise direction by Lenz's rule.