It is just a demonstration of the Meisner effect for a superconducting
material. In fact, if the pictured apparatus had the superconducting material
(the black cube) attached to the dish that holds the liquid nitrogen, the
entire thing could be tipped on its side and the rotating magnet would still
hover directly over the cube, it would not slide out of the magnetic field.
That's way more impressive than just floating.
Dennis
Posted by Bob Chilcoat on March 17, 2006, 10:45 am
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The black block is a high-temperature superconducting material. The silver
disk is a strong magnet. When the superconductor is cooled with liquid
nitrogen and becomes superconduction, any movement of the magnet generates
an opposing eddy current in the superconductor. By Lenz's law, this eddy
current produces an opposing magnetic field that opposes any movement of the
magnet. Since there is no resistive loss in the superconductor, the magnet
just stays where it is left.
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