Teaching Minds-On Experiments on Electromagnetism in Secondary Schools

Lorentz force
Homopolar motor

Simple 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.