5K20.40 Eddy Current Levitator


Eddy currents


A magnet levitates over a rapidly spinning aluminum disc. A 1/4-20 brass nut may be used to demonstrate that the levitation is an eddy current effect. Note: with a video camera, this demonstration is appropriate for large lecture halls.



  • [1] Magnet and brass nut attached to pieces of card stock
  • [1] Aluminum disc attached to a motor
  • (Optional) [1] Video camera

Classroom Assembly

  1. Place the magnet on the aluminum disc and hold on to the end of the piece of card stock.

Important Notes

  • The disc spins at several thousand RPM. DO NOT TOUCH.
  • Keep the magnet in the center of the disc. If the magnet comes too close to the edge it can skip and shatter. If it comes too close to the center, it can stick suddenly to the magnetic screws in the center.
  • The magnet is strong and brittle. Handle with care.


  1. Turn on the motor. The magnet will levitate.
  2. Turn off the motor.
  3. Place the brass nut on the aluminum disc and hold on to the end of the piece of card stock.
  4. Turn on the motor. The brass nut will not levitate.


Additional Resources


  • PIRA 5K20.40 
  • Demonstration Manual for 12-in-1 Apparatus; DHP El-1; DaR B-290 
  • Thomas D. Rossing and John R. Hull, Magnetic Levitation, TPT 29, 552-562 (1991)


  • Don't attempt this at home!

Last revised

  • 2018


  • A Nd-B-Fe magnet (1/2 inch diameter, 1/4 inch thick) is attached to a piece of card with double sided tape.

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If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.