INDUCTION DISK

Demo Number	197
Location	Shelf 37
Description	This is a metal disk that has been balanced on a pin-sized tip to eliminate friction. When a spinning magnetic field (magnet mounted in a drill) is applied to the disk as shown in the picture, it starts spinning via the induction current formed on the disk. When a strong magnet is held around the rim of the disk, it will start slowing down due to magnetic braking.
Related Demos	337
Tips	Procedure: Hold the magnet-drill assembly close to the balanced disc and operate the drill. The magnet exerts a torque (via eddy currents) on the disc, causing it to spin in the same direction as the magnet. The disk can be brought up to high speed very very quickly. This demonstrates one method used in speedometers. There is also a second disk made of the same material that has slits cut along it to eliminate eddy currents from forming. For best results, remove the aluminum disc from the magnet, oil the base at the contact point, and hold the magnet very close to the disc.

Colorado State University