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dynamo working? Answered

working principle of bicycle dynamo



What?(is the question)


The usual answer to this question is, Faraday's Law of Induction.
You know,the one about a coil of wire, with a changing magnetic field inside of it, with the induced voltage proportional to the number of turns of the coil, and also proportional to the rate of change of the magnetic flux through the coil.

The Wikipedia article on Dynamo says that a dynamo is an alternator with a commutator, and the commutator is there because this is a machine intended to produce DC (direct current). 

However in the vernacular, I think the words generator, alternator, dynamo, are kind of used interchangeably.   For example, I think those "bicycle dynamos" were actually alternators, producing AC (alternating current).

One trick that gets used a lot for small hand-cranked type generators, is simply to drive a permanent magnet DC. A motor like this wants to turn fast, so some sort of gearing is needed to increase the rotational speed, from the slow rotational motion of a hand turning a crank.  

An old cordless drill often contains gears and a motor suitable for this, and can be turned into a hand-cranked dynamo/generator, as shown in this instructable:

They ain't been dynamos for many years AIUI.

Same principle as any dynamo, even the huge giant down there at the power station.