Stirring up a magnetic paradox
作者:
Donald E. Fahnline,
期刊:
American Journal of Physics
(AIP Available online 1977)
卷期:
Volume 45,
issue 11
页码: 1020-1021
ISSN:0002-9505
年代: 1977
DOI:10.1119/1.10964
出版商: American Association of Physics Teachers
数据来源: AIP
摘要:
A commerical magnetic stirrer provides a convenient rotating horseshoe magnet for several well‐known demonstrations of induced eddy currents and Lenz’s law such as the spinning of a nonferromagnetic metal top or coin and the operation of a speedometer. A new demonstration is paradoxical: A steel ball rolls in a circle either in the same direction as the rotation of the stirrer magnet or in the opposite direction. That an aluminum cone or rivet also rolls in the opposite direction shows that the latter effect is due to induced currents, but this seems to violate Lenz’s law.
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