Teaching Minds-On Experiments on Electromagnetism in Secondary Schools Lorentz force Homopolar motor
homopolar motor made with drywall screw, alkaline cell, wire, and
neodymium disk magnet. The screw and magnet contact the bottom of the
battery cell and are held up by magnetic attraction.
In the homopolar motor, the electric current produced by the battery
moves radially through the disk magnet, which has a magnetic field
along its longitudinal axis. The resulting Lorentz force in the
tangential direction produces a torque in the magnet, which is free to
rotate with the attached screw. 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.