PURPOSE: A number of demonstrations involving concepts in magnetic induction.

DESCRIPTION: Several induction experiments are possible with this device:

(1) JUMPING RINGS: Placing a ring over the extended primary coil core and switching it on causes the ring to jump. A smaller ring will jump higher. Cool the ring in liquid nitrogen to get a really great jump, but be careful about hitting the rear projection screen. Broken metal rings and wooden rings are unaffected.

(2) RESISTIVE HEATING: Verify that there is resistive heating in the secondary ring by having a student hold it down until it gets too hot to touch!

(3) A light bulb on a small coil lights up when the coil is moved over the extended core.

(4) A secondary coil with small light bulb placed in a beaker on top of the secondary coil will remain lit when it is covered by water in the beaker.

Talk about magnetic levitation and MAGLEV trains after doing this experiment.

SUGGESTIONS: This experiment is fairly complicated. Read about it in detail before attempting to explain it to your class. See Question of the Week #182 for suggestions on using this demonstration to enhance class involvement.

REFERENCES: (PIRA 5K20.30) See Demonstration Reference File for articles discussing the theory of this device as well as information regarding applications such as the MagLev train. Click here for the design plans of a nice Thomson Coil constructed by Dr. Karl Trappe of the University of Texas.

EQUIPMENT: Thomson's coil with accessories.

SETUP TIME: None.