Make Homopolar motor

A homopolar motor has a magnetic field along the axis of rotation and an electric current that at some point is not parallel to the magnetic field. The name homopolar refers to the absence of polarity change.


The homopolar motor was the first ever device to produce rotation from electromagnetism itself. It was first built and demonstrated by Michael faraday in 1821 at the Royal Institution in London.

Homopolar motors necessarily have a single-turn coil, which limits them to very low voltages

It is not necessary for the magnet to be electrically conductive, or to move. One can attach the magnet to the battery and allow the wire to rotate freely while closing the electric circuit even at the axis of rotation. Again, where at some point along the electric loop the current in the wire is not parallel to the magnetic field, there occurs a Lorntz force that is perpendicular to both. This Lorentz force is tangential and produces a torque in the wire, so that the wire rotates.

In contrast to other electrical motors, both the orientation and magnitude of the magnetic field and the electric current do not change.

Like most electro-mechanical machines a homopolar motor is reversible so that when electrical energy of a suitable kind is put into its terminals, mechanical energy can be obtained from its motion and vice versa, (see homopolar generators for details on construction and theory of operation)