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At it's simplest, electricity generation is achieved by induced voltage due to a changing magnetic field. In a vacuum in the absence of friction, would the initial spin imparted to the rotor of a generator ever come to a halt?

i.e. Would a traditional generator in space generate electricity perpetually (notwithstanding component failure etc)?

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No, because the process of transferring the voltage into a useable form or device will reduce it. In other words, under perfectly idealized conditions (which are impossible), yes it might spin forever, but as soon as you try to use your generator to power a device, you'll slow it down.

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It is also worth noting that without superconducting wire throughout, the resistance of the wire would dissipate the concentration of energy of the initial conditions. Additionally, depending on the arrangement of the equipment, Lenz's law would slow the rotor over time and eventually stop the system. – AdamRedwine Sep 20 '11 at 11:48
So, why are big generators then often filled with hydrogen gas? :=) – Georg Sep 20 '11 at 13:50
Georg, your usual curmudgeonliness is one thing but these kind of comments are really unconstructive. – user2963 Dec 11 '11 at 15:47
@AdamRedwine: Lenz's law only gives the direction of the force in Faraday's law. – Hans-Peter E. Kristiansen Dec 11 '11 at 15:53

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