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 upward to coil A . When coil A start rotating at t = 0, the current in A is constant along clockwise direction by Lenz.s rule.