Thomson's Coil


A number of demonstrations involving concepts in magnetic induction.


Thomson's coil with accessories.



This experiment is fairly complicated. Read about it in detail before attempting to explain it to your class.




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 t


Harvey E. White and Hans Weltin, Electromagnetic Levitator, AJP 31, 925-929 (1963). E. J. Churchill and J. D. Noble, A Demonstration of Lenz' Law?, AJP 39, 285-287, (1971).