Electrical Projects The simplest electric motors are dc motors, and these find many applications in small household appliances. They are often found in electric toothbrushes and small, portable hair dryers, for example.

The magnetic field for a motor may be provided by a permanent magnet. When a dc level is "wiped" onto the commutator (the separated contacts connected to the coils of wire) by a set of brushes (not shown), the current flowing through the coils of wire creates magnetic fields around the coils that are either opposed or attracted by the poles of the permanent magnet. Since the permanent magnets are stationary, the attraction and repulsion of magnetic fields between the coils of wire and the permanent magnetic field causes the coils of wire to rotate. The stationary magnetic field is called the field, and the rotating coils of wire are called the armature. In an actual motor, the armature consists of several hundred or thousand feet of wire wound in a series of coils. The commutator is the point where the brushes connect the dc voltage to the armature. The bars of the commutator are insulated from each other by mica insulation between them, and the coils of wire on the armature are usually insulated by enamel or lacquer insulation on the wires.




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October 13, 2008