PURPOSE: To demonstrate Lenz's law in a simple and direct way.
DESCRIPTION: Thrust one pole of a strong horseshoe magnet into a coil (video 1 below), or quickly withdraw it from inside the coil (video 2 below). A current is induced in the coil that opposes the motion of the magnet, and the reaction force on the coil results in the coil being either pushed or pulled in the same direction that the magnet was moved. Move the magnet in and out of the single turn aluminum coil (video 3 below) Disconnect the hook for the single turn coil. No current can flow so no force is created (video 4 below).
SUGGESTIONS:
See Question of the Week #170 for information on using this demonstration to enhance class involvement.
REFERENCES: (PIRA 5K20.26)
EQUIPMENT: Stand with one-turn and five-turn coils, horseshoe magnet.
SETUP TIME: None.
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