Question

In above shown figure, find out which best describes the direction(s) of the current induced in the loop (looking down on the loop from above) if a permanent bar magnet is pulled upward with a constant speed through a loop of a wire.

• A. Always clockwise
• B. Always counterclockwise
• C. First clockwise, then counterclockwise
• D. First counterclockwise, then clockwise
• E. No current will be induced in the loop.

Answer 1

Answer: (C)

First clockwise, then counterclockwise

The direction of induced can be given by Lenz's law ,when the $N$ pole of magnet is approaching the loop in first condition (before), the lower face of loop will also become $N$ pole to oppose the motion of magnet by repulsion, ( due to Lenz's law ) therefore the upper face would be $S$ pole, it means current in clockwise direction.

When the $S$ pole of magnet is going away from the loop in second condition (after) the upper face of loop will become $N$ pole to oppose the motion of magnet by attraction, (due to Lenz's law) therefore the upper face would be $N$ pole, it means current in counterclockwise direction.