Homopolar motor

A homopolar motor made with a battery cell and a coiled wire.
DIY simple homopolar motor made with a drywall screw, a battery cell, a wire, and a disk magnet. The magnet is on the screw head. The screw and magnet make contact with the bottom of the battery cell and are held together by the magnet's attraction. The screw and magnet spin, with the screw tip acting as a bearing.

A homopolar motor is a direct current electric motor with two magnetic poles, the conductors of which always cut unidirectional lines of magnetic flux by rotating a conductor around a fixed axis so that the conductor is at right angles to a static magnetic field. The resulting force being continuous in one direction, the homopolar motor needs no commutator but still requires slip rings.[1] The name homopolar indicates that the electrical polarity of the conductor and the magnetic field poles do not change (i.e., that it does not require commutation).

  1. ^ Lynn, L. (1949). "§197-§204 'Acyclic or Homopolar Machines' in Section 8 - Direct-Current Generators and Motors". In Knowlton, A.E. (ed.). Standard Handbook for Electrical Engineers (8th ed.). McGraw-Hill.