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Al Tobias (wat4y) - Office: Gibson S123 & Physics 218, (434) 924-0538

Physics Demo Manual

Demonstrations are cataloged according to PIRA Bibliography


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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 Electric Fields And Potential
 Current and Resistance
 Electromotive Force And Current
 DC Circuits
 Magnetic Materials
 1x 2x 4x Coils and Bar Magnet
  video  - Hanging Ring and Magnet
 Flash Bulb Coil
  video  - LED Coil
  video  - Eddy Current Pendulum
  video  - Lenz's Law and Eddy Currents
  video  - Eddy Current Tube
  video  - Jumping Ring
 Eddy Current Levitation
 Eddy Current Levitation 2
 Eddy Currents 2
  video  - Transformers
 Electric Motor
 Hand Crank Generator
 Bicycle generator
 Complex Circuits
 Semiconductors And Tubes
 Transmission Lines and Antennas

Eddy Current Levitation


To illustrate eddy current levitation of a magnet above a moving conductor.


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.


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.


  • Motor Driven Circular Metal Disk
  • Strong magnet attached to a duct tape strip