Description: A magnet levitates over a rapidly spinning aluminum disc.

A Nd-B-Fe magnet (1/2 inch diameter, 1/4 inch thick) is attached to a piece of card with double sided tape. Holding the card, place the magnet on the aluminum disc. Turn on the motor and watch the magnet levitate. Keep the magnet away from the center or too close to the edge of the disc. A 1/4-20 brass nut may be used to demonstrate that the levitation is an eddy current effect.

Cautions: The disc spins at several thousand RPM. The screws in the center of the aluminum disc are magnetic. The magnet is strong and brittle - handle with care.

Concepts demonstrated: Eddy currents

Setup Time: short

Difficulty/Commitment: straightforward

Visibility: needs a video camera

References: 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)