A coil lies flat on a tabletop in a region where the magnetic field vector points straight up.The magnetic field vanishes suddenly.When viewed from above,what is the direction of the induced current in this coil as the field fades?
A) counter-clockwise then clockwise
B) clockwise then counter-clockwise
C) clockwise
D) counter-clockwise
E) There is no current induced in the coil.

Question

Quizplus · Accepted Answer

According to Lenz's law, the induced current in the coil will flow in such a way 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 original magnetic field direction. When viewed from above, and given that the original magnetic field was pointing upwards, the induced current must flow counter-clockwise to create a magnetic field that also points upwards, opposing the decrease.

A Coil Lies Flat on a Tabletop in a Region