Conceptual Physics (12th Edition)

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

Chapter 25 - Think and Discuss: 93

Answer

See below.

Work Step by Step

When you move a conducting sheet through a magnetic field, currents are induced in the sheet, as predicted by Faraday's law. These swirling "eddy currents" cause a magnetic field that interacts with the permanent magnet, and this slows down the moving sheet. Cardboard doesn't conduct electricity, so there are no eddy currents, and no slowdown.
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