PURPOSE: To show damping of pendula due to eddy currents.
DESCRIPTION: Pendula with bobs of different materials and geometries are swung through the poles of a strong horseshoe magnet. The amount of damping is greater for those bobs in which strong eddy currents can flow. Bobs include, solid copper, copper loop, broken copper loop, laminated copper, copper with central hole, and wood.
SUGGESTIONS: For an extremely dramatic effect, dip the bob into liquid nitrogen before letting it swing; it stops IMMEDIATELY!
EQUIPMENT: Eddy current magnet with various pendula.
SETUP TIME: None.
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