What happens when you drop a magnet down a copper tube?
Eddy Current Tubes -- Drop the Magnets down the tube. An eddy current is set up in a conductor in response to a changing magnetic field. Lenz's law predicts that the current moves in such a way as to create a magnetic field opposing the change; to do this in a conductor, electrons swirl in a plane perpendicular to the changing magnetic field.You don't need to understand all that to see that it's neat. The reaction from everyone I've shown this to is, "I'll have to try that!" (via VideoSift)
Because the magnetic fields of the eddy currents oppose the magnetic field of the falling magnet; there is attraction between the two fields. Energy is converted into heat. This principle is used in damping the oscillation of the lever arm of mechanical balances.