Concepts

Eddy currents

Overview

A magnet levitates over a rapidly spinning aluminum disc. As a control experiment, a brass nut may be used to demonstrate that the levitation is an eddy current effect. 

Details

Equipment

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

Classroom Assembly

1. Plug in the motor.

Important Notes

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

Script

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

Additional Resources