A coil lies flat on a table top in a region where the magnetic field vector points straight up. The magnetic field vanishes suddenly. When viewed from above, what is the sense of the induced current in this coil as the field fades?
A) The current flows clockwise initially, and then it flows counterclockwise before stopping.
B) There is no induced current in this coil.
C) The induced current flows counterclockwise.
D) The induced current flows clockwise.

Question

Quizplus · Accepted Answer

According to Lenz's law, the induced current in the coil will flow in such a direction as to oppose the change that produced it. Since the magnetic field is decreasing, the induced current will flow in a direction that tries to maintain the magnetic field inside the coil. Given the magnetic field points straight up and is decreasing, the induced current will flow counterclockwise when viewed from above, to try to create a magnetic field that points upwards, opposing the decrease.

A Coil Lies Flat on a Table Top in a Region