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Uploaded on Jan 29, 2012
A magnet is dropped through a conducting cooper ring. As the magnet falls under gravity, an eddy current is induced in the ring that tries to keep the magnetic flux through the area of the ring constant. This corresponds to a field that produces a force that opposes the motion of the magnet: as the magnet approaches from above, and the induced current (represented by the beads) generates a field that pushes the magnet upwards from below.
Once the magnet falls through the ring, the direction of the eddy current changes to produce a field that tries to pull the magnet upwards from above. Since the resistance of the ring is finite and the magnet is heavy, the flux through the ring does not stay constant, and the relatively small magnitude of the induced field does not generate a force strong enough to prevent the magnet from falling through.
The motions of the field lines in this animation are in the direction of the local Poynting flux vector.