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Levitation Demonstrates Superconductivity
Procedure
Set the specially adapted overhead projector on its back. Be sure to attach the extra mirror assembly that converts the overhead to vertical use.Place two styrofoam cups up-side-down on the table, one cup in front of the overhead. Place the large black superconductor on the cup in front, and the small magnet on the second cup.Pour liquid nitrogen onto the base of both cups. The rim of the base should hold enough liquid nitrogen to cool the magnet and superconductor.Once the magnet and superconductor have cooled to the temperature of the liquid nitrogen (this may take a few minutes and several refills of the cup base with liquid nitrogen), using plastic forceps, place the magnet about 2mm above the center of the superconductor. The magnet will remain suspended until it warms to above its critical superconducting temperature.Use care to avoid hitting the glass of the projector with liquid nitrogen; the glass could shatter. The superconducting disc and cobalt magnets are available from Edmund Scientific. Listed under educational demonstrations.
References:
J. Chem Ed., 64, 836-853
