Al Tobias (wat4y) - Office: Gibson S123 & Physics 218, (434) 924-0538
Demonstrations are cataloged according to PIRA Bibliography
PLEASE REQUEST DEMOS WELL IN ADVANCE
Due to Physics Building renovations, the lead time to set up demo requests has increased due to the need to transport equipment across campus. Please be kind and let me know well ahead of time what you need.
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You have selected the following Demos:
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Eddy Current LevitationPurpose:To illustrate eddy current levitation of a magnet above a moving conductor.Procedure:Show that the strip of duct tape is not strong enough to support the magnet by holding the far end of the strip and allowing the magnet to fall onto the metal disk. Remove the magnet and spin up the metal disk. Again lower the magnet onto the disk. In this case it should "float" above the surface about 1/2". With the magnet near the edge and near its greatest height, turn off the motor and slow down the disk. As the disk slows, the magnet should fall down until, when the disk is nearly stopped, the magnet should be resting on the disk itself. There are induced currents in the disk caused by the magnet and the relative motion - these currents result in an opposing magnetic field and thus the force of levitation. This principle is used for the suspension of high speed trains in Japan and elsewhere. This allows for the possibility of high speed travel without large amounts of mechanical shock due to imperfections in the track.Hints:Non-magnetic metal washers wrapped in a similar duct tape sleeve are available to demonstrate that they wouldn't float even on top of the spinning disk.Equipment:
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