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# How does a dynamo work?

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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. A commutator can turn the alternating current into direct current pulses, a common practice in early days before alternating current became the standard.

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The dynamo (Greek for ?power?) 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.

Dynamos were the first type of electric generators. When engineers started understanding and using alternating current, the dynamo fell out of favor because the commutator requires mechanical contacts that rub against the armature. These contacts wear down over time, so most modern electrical generators, that need direct current output, simply convert the alternating current using diodes. Automobiles use this system to provide on-board power and charge the car?s battery.

## Related Questions

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A bicycle dynamo works by converting the mechanical motion of the rotating wheel into electrical motion with the use of a magnet. The dynamo contains a permanent magnet wound with coils of insulated wire. When the magnet rotates, it creates a changing magnetic field, which generates electricity in the wire.

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Windmills produce electricity by electromagnetic induction, the process in which the movement of magnets in a magnetic field generates electricity. In a windmill, when wind moves the blades of the windmill that move the rotor, the rotor rotates a shaft that holds magnets in the magnetic field of the generator, generating alternating current that is sent along power lines.

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Florida State University defines Lenz's Law as an induced electromotive force that generates a current that induces a counter magnetic field opposing the magnetic field generating the current. Lenz's Law was first discovered by the Russian physicist Heinrich Lenz in 1834.