A student holds a bar magnet so that its north pole faces directly toward the center…
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A student holds a bar magnet so that its north pole faces directly toward the center of a horizontal, circular conducting loop that lies flat on a table. The student first pushes the magnet straight toward the loop, then brings it to rest for several seconds directly above the center of the loop, and finally pulls the magnet straight back to its original position.
Assume the magnet’s axis is aligned with the loop’s central axis and that you are looking down on the loop from above the magnet.
(a) While the magnet is moving toward the loop, indicate whether the induced current in the loop is clockwise, counter-clockwise, or zero. Justify your answer by describing the change in magnetic flux through the loop and the magnetic field created by the induced current.
(b) While the magnet is momentarily at rest above the loop, state the direction of the induced current and justify your answer.
(c) While the magnet is moving away from the loop back to its starting point, indicate the direction of the induced current and provide reasoning similar to part (a).