Electricity & Magnetism

Hysteresis Motor

The precise timing of motors like this one makes them useful in clocks, timers and recording equipment. This particular motor was originally used to pump water in an aquarium. The wheel of this motor is turned by a changing magnetic field. The coil of wire at the base of this motor carries ordinary household electricity, creating a magnetic field that changes direction 60 times every second. The wheel responds to this magnetic field, but not immediately. The sluggish response (called hysteresis) keeps the magnetism of the wheel slightly out of step with the electromagnet.