If you put a generator in space, where there is no gravity, and the axle was suspended with magnets, like a Maglev train, it would eliminate the outside forces that could stop the generator. You could spin it once and it could generate electriciy forever. That contradicts the law that energy may not be created or destroyed. Is there a hole in my argument?
This is hypothetical, I know we won't use this because we would need a 62+ mile cord to use the electricity, I just need input from someone who knows the answer.
This is hypothetical, I know we won't use this because we would need a 62+ mile cord to use the electricity, I just need input from someone who knows the answer.
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The flaw is that gravity is not the only source of energy loss in a generator. There is friction in the bearings, resistance in the wires and so on.
The laws of thermodynamics are probably more relevant than Newton's laws, and they say that no energy transfer process is 100% efficient, some energy is always lost as heat.
And, certainly, there would be resistance losses in the 62+ mile wire.
So it's a great thought experiment and an interesting idea... but many smart people have been trying for hundreds of years to design a 'perpetual motion machine' that gives us energy for nothing without success...
But keep thinking!
The laws of thermodynamics are probably more relevant than Newton's laws, and they say that no energy transfer process is 100% efficient, some energy is always lost as heat.
And, certainly, there would be resistance losses in the 62+ mile wire.
So it's a great thought experiment and an interesting idea... but many smart people have been trying for hundreds of years to design a 'perpetual motion machine' that gives us energy for nothing without success...
But keep thinking!
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People are so quick to point the finger at friction! There is actually a very simple, non-thermodynamic reason why this isn't going to work.
Even if you could arrange things so that no energy was lost to friction, all you would achieve is a potential difference between the terminals of the generator. As soon as you connect up a load, current will begin to flow through the generator's coil. By Lenz's law (http://en.wikipedia.org/wiki/Lenz's_law ) this current will generate a magnetic field within the generator which will oppose the rotation, gradually slowing the generator down. Eventually it will stop completely, and no more current will flow.
In fact, from basic energy considerations all you're doing is converting the rotational kinetic energy you initially put in, into electrical energy. That makes it immediately obvious that the generator must slow down as you draw current from it, and that the supply of energy is limited.
Even if you could arrange things so that no energy was lost to friction, all you would achieve is a potential difference between the terminals of the generator. As soon as you connect up a load, current will begin to flow through the generator's coil. By Lenz's law (http://en.wikipedia.org/wiki/Lenz's_law ) this current will generate a magnetic field within the generator which will oppose the rotation, gradually slowing the generator down. Eventually it will stop completely, and no more current will flow.
In fact, from basic energy considerations all you're doing is converting the rotational kinetic energy you initially put in, into electrical energy. That makes it immediately obvious that the generator must slow down as you draw current from it, and that the supply of energy is limited.