Lenz's Law

Lenz's law states that an induced electromotive force always gives rise to a current (shown by red arrows) whose magnetic flux opposes the original flux due to the field of an approaching permanent magnet. As a consequence, when a strong magnet is dropped through an aluminum or copper tube, it moves much more slowly because of the opposing induced force.


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In the graphic, the red half of the magnet represents the north pole and the blue half represents the south pole. At the bottom, an ammeter shows the flow of electric current.
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