The main parts of a DC electric motor are as follows:
The main shell of the DC motor is really nothing but a metal shell with two permanent magnets mounted on either side. These magnets have opposite polarities. Within this shell, the armature sits. The enclosure is sealed up and electrical contacts mounted on the outside of the shell make contact with the commutator, which contacts the armature.
The armatureis the part that spins; Basically it's a big nest of coils which become an electromagnet when electricity reaches them through the commutator. The resulting magnetism makes the armature spin because of the permanent magnets surrounding it. An output shaft leading out of the motor's shell is attached to the armature, and since the armature spins, so does the shaft; You attach stuff to this shaft to make the motor useful.
The commutator is the part that makes contact with the incoming electrical contacts, and also with the armature. (It sits between the armature and the incoming electrical connection). It works to reverse the direction of electricity's travel through the armature every half-turn.
In some larger electric motors, brushes are used to make contact between the commutator and the armature. In smaller motors the commutator usually touches the armature directly.
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