If you place a metal ring in a region in which a magnetic field is rapidly alternating, the ring may become hot your touch, why?
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1 answer
An EMF will be induced in the ring due to the changing magnetic field passing through it. This will cause an "eddy" current to flow back and forth in the ring, resulting is resistive heating. Since the induced AC EMF is constant, the power absorbed and deposited in the ring (V^2/R) is inversely proportional to the resistance of the ring, R. The low resistance of the metal in the ring (usually gold/copper alloy) means it heats up a lot.