Conceptual Physics (12th Edition)

Published by Addison-Wesley
ISBN 10: 0321909100
ISBN 13: 978-0-32190-910-7

Chapter 25 - Think and Explain - Page 482-483: 63


The electromagnet is ac.

Work Step by Step

The ac magnetic field continually changes the magnetic field in the copper ring. This induces a current in the copper ring, turning it into an electromagnet. The ring's field continually opposes the original field produced by the iron-core electromagnet, and the ring is continually repelled by it. The ring hovers at a position at which the repulsive force just balances the copper ring's weight.
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