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1 what is called dynamo 2 compare the resistivities of conductor and insulators at the same temperature
Dynamos were the first type of electric generators. Dynamos produce electric current by rotating a wire within a magnetic field. Another method rotates a permanent magnet around coils of wire. Both processes produce alternating current because the wire passes between two magnetic poles every half turn.
The dynamo includes a fixed magnetic field called a stator, an armature wrapped with the wire that rotates within the stator, and a commutator on the armature that acts like a switch between the positive and negative current generated with each rotation, sending current in only one direction with each half rotation. Smaller dynamos, like those found on bicycles, use permanent magnets, while larger dynamos need electromagnets.


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