A circular coil lays flat on a horizontal table in a region where the magnetic field is straight down. The magnetic field is suddenly removed. When viewed from above, what is the direction of the current in the coil as the field is removed?
A) clockwise
B) clockwise initially, then counter-clockwise before going to zero
C) counter-clockwise
D) There is no induced current.

Question

Quizplus · Accepted Answer

When the magnetic field is suddenly removed, Lenz's law states that the induced current will flow in a direction that opposes the change that produced it. Since the magnetic field was initially pointing downwards, the induced current will flow in a direction that would have created a magnetic field pointing upwards to oppose the loss. When viewed from above, this means the current must flow clockwise to create an upward magnetic field through the coil.

A Circular Coil Lays Flat on a Horizontal Table in a Region