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If you spin a generator in weightless space could you generate infinite power?

Of course the friction would be a issue but couldn't there be ways to reduce this in a weightless environment?

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    $\begingroup$ What research have you done? Note that throughout Stack Exchange we have a basic prior research requirement (see e.g. How to Ask) in a bid to avoid trivial questions and subsequently vague answers they tend to produce (the latter however excusable, because it's simply too broad to discuss fundamental principles in a general sense also in much detail). $\endgroup$ – TildalWave Jan 7 '15 at 18:17
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    $\begingroup$ A generator does not generate power; a generator converts mechanical power to electrical power. Even in the case of an ideal (lossless) generator, the power output cannot exceed the power input. $\endgroup$ – Alfred Centauri Jan 8 '15 at 2:53
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Friction is ultimately where most power is lost in a generator system or any other mechanical system. The pull of gravity against interlocking objects, pressing them against each other, certainly causes some friction. The medium in which objects move also causes friction. In the weightless vacuum of space, both of these kinds of friction can be reduced to nearly zero, which is why we can have things like relatively stable orbit.

On Earth, engineers used to try to produce perpetual motion machines. To do this, the friction that would otherwise gradually slow down the machine must be reduced to a level that is negligible compared to the momentum in the machine. Even when this is achieved, you don't really have perpetual motion, unless friction is actually zero, but you could have the appearance of perpetual if the ratio of friction to momentum is low enough. This is what can be achieved in the vacuum and weightlessness of space - apparently perpetual motion.

Perpetual motion does not mean infinite energy. With your generator idea, you are trying to imagine something that escapes the limitations of the Law of Conservation of Energy. You are imagining a system in motion which stays in motion, and you recognize that motion is a kind of energy. But what you want to do next is to remove some of that energy and apply it to something else. When you do so, your system will slow down by at least as much as the energy you have used. When you generate electricity by spinning a magnet inside a coil of wire, the energy you get comes from pushing electrons down that wire. But what pushes the electrons? Have you ever used a device that generates some kind of power by turning a hand-crank? Do you ever wonder why there is so much resistance to turning that crank? It's essentially because you are pushing electrons with your hand. By turning the magnet, you induce a current in the wire. By inducing the current, you generate a magnetic field. That new magnetic field resists the field of the magnet you are turning. Ultimately, what you are feeling is the resistance of the momentum of those electrons wanting to remain "at rest".

But simply moving them is not the only work you have to do actually. Did you know there is friction at that atomic level? If you put a lot of power through a wire, the wire gets hot. That's from a kind of friction called electrical resistance. So what you would find if you have a "perpetually" spinning magnet in a space station is that as soon as you move a coil of wire over it, it will very quickly stop. If you had a light bulb attached to that wire in a completed circuit, it would glow briefly. You would also feel a tug on that wire. Then your energy is spent. The motion was transformed into heat, light, and the tug you felt on the wire. The end.

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  • $\begingroup$ but what if we dont apply loa directly to that generator.what if we simply store that energy? $\endgroup$ – user14561 May 28 '16 at 12:58
  • $\begingroup$ @zeehasham Continuing motion of a spinning magnet is a kind of kinetic energy. Stored energy is potential energy, regardless of how you store it. Transforming kinetic energy into potential energy is a very basic physics concept that you can learn about from a variety of sites that Google can find for you. When this transfer happens, the total amount of stored energy cannot be greater than the kinetic energy which was absorbed. The total energy present cannot increase in such a transfer. $\endgroup$ – Mark Bailey May 31 '16 at 17:16
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No. Although it is weightless, its mass remains the same. Therefore, the effective angular momentum & energy required to spin it up to speed is not changed.

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