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Homopolar Motor


A permanent magnet is used to provide the external magnetic field in which the conductor will turn, and a battery causes a current to flow along a conducting wire. The conducting wire will revolve around the battery like a motor.

Apparatus :

- Battery - Conducting wire - Disc permanent magnets




1. Attach magnets to negative terminal of battery as shown. 2. Balance the wire on the positive terminal. You may need to give it a slight push. 3. If it doesn't work, bend the two arms of the wire until they touch the magnets.

Principles of Operation : The homopolar motor is driven by the Lorentz force: as it moves through a magnetic field, the conductor is pushed through a magnetic field by opposing forces. This force induces a torque around the axis of rotation. Because the axis of rotation is parallel to the magnetic field, and the opposing magnetic fields do not change polarity, no commutation is required for the conductor to keep turning. This simplicity is achieved at the cost of not being able to have more than one coil turn, which makes this configured homopolar motor unsuitable for most useful applications.

Last Updated on : 02/23/16


Demo room information

Location —-
Maker Unknown
Current State Working
demonstrations/5_electricity_and_magnetism/5k_electromagnetic_induction/5k40_motors_and_generators/homopolar_motor/start.txt · Last modified: 2019/02/14 23:33 (external edit)