Metal brushes and a flat commutator switch power to the rotor coils.
2.
The force between the two magnetic fields tends to rotate the motor shaft . The commutator switches power to the coils as the rotor turns, keeping the magnetic poles of the rotor from ever fully aligning with the magnetic poles of the stator field, so that the rotor never stops ( like a compass needle does ), but rather keeps rotating as long as power is applied.
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