A square loop of wire with a small resistance is moved with constant speed from

Question

A square loop of wire with a small resistance is moved with constant speed from a field free region into a region of uniform B field (B is constant in time) and then back into a field free region to the left. The self inductance of the loop is negligible When entering the field the coil experiences a magnetic force to the right. Upon entering the field, a counterclockwise current flows in the loop. While the loop is entirely in the field, the emf in the loop is zero. When leaving the field the coil experiences a magnetic force to the right.

Explanation / Answer

a.) True. The induced emf always tries to oppose the change in the magnetic flux, and hence the loop will experience a magnetic force to the right while entering the field to oppose the increase in the magnetic flux.

b.) False. While entering the loop the magnetic flux in the upward direction is increasing. And since the induced emf always tries to oppose the change in the magnetic flux, the induced current should produce a magnetic field in the downward direction to oppose the change. This is possible if the current is in the clockwise direction according to the right-hand rule.

c.) True. Change in magnetic flux induces emf, and since the magnetic flux remains constant after entering the field, the emf will be zero.

d.) True. The induced emf always tries to oppose the change in the magnetic flux, and hence the loop will experience a magnetic force to the right while leaving the field to oppose the decrease in the magnetic flux.

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