Conceptual Physics (12th Edition)

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

Chapter 25 - Think and Explain: 55

Answer

See below.

Work Step by Step

The ac magnetic field induces "eddy currents" in the metal piece. The field that results induces a current in the strategically placed large pickup coils, which sets off an alarm.
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