Simple Question

[Ahwleung]

This question probably has a very simple answer but I've been wondering it for quite a while:

My question is that if electricity is generated simply by rotating a magnet around a coil of wire, what would happen if this device were placed in space (or a gravity and vacuum-less void) and spun rapidly? Would not an infinite energy device be created? According to Conservation of Energy this would be impossible, so would the production of electricity actually slow the spinningmagnet?

[Buffy]

No, because the interactions of the electrical fields--that do the work that generate the electricity--create "friction" to put it colloquially, so eventually it will slow down. You'll probably need a phyiscal mechanism to keep the electromagnet parts close enough to eachother--they'll try to push eachother away--and that mechanism (whether physical with ball bearings, or yet another electromagnet) will also create friction, and thus it will eventually stop without further input from outside the system.

There is no naked lunch,
Buffy

[Jay-qu]

you answered your own question

Note that it is normally the coil that is spun.

When a current is set up in the wire it will experience a force also, but in the opposite direction to the way its already spinning. This will slow it down and eventually make it stop.

[Boerseun]

Originally Posted by Buffy

There is no naked lunch

Damn...

[EStein]

Originally Posted by Ahwleung

....what would happen if this device were placed in space (or a gravity and vacuum-less void) and spun rapidly? ...

A "vacuum-less void" is not as strange as it first appears. In the universe, there are no real voids or vacuums. Matter pops in and out of existence like magic. You could just as well have said "a void-less vacuum"--which isn't really what you meant to say so this exercise of mine is pointless. Actually, everything is pointless. To have a point would imply a singularity. It would be like trying to divide by '0' but you can't really divide by '0'; it would be pointless....doh!!

[Qfwfq]

Originally Posted by Ahwleung

so would the production of electricity actually slow the spinningmagnet?

Of course! There's no messing with energy conservation.

Even with a total absence of friction, the generated current causes its own magnetic field which opposes the motion. This specific case of the energy conservation principle is called the Lenz law. An electric generator is simply converting between mechanical and electric energy.

[EStein]

Originally Posted by Qfwfq

Even with a total absence of friction, the generated current causes its own magnetic field which opposes the motion.

That is correct. When I was a kid, a friend of mine and I had an antique crank generator from an old phone. Originally, when connected inside of a phone box, it would ring all lines in the circuit(what was known as a "party line"). People would know who the call was for by a code of rings. For example, 2 longs and a short ring or long, long, short--all codes(instead of phone numbers) for the party with whom you wished to speak. Anyway, the harder you cranked the generator, the more resistance you could feel through the crank and the more 'juice' that flowed through the wires. It probably produced an alternating current. One day, while playing with the generator, we saw a fellow several blocks up the street who was washing his car, barefoot. We put the wires in the soapy water trail that was flowing past us and cranked furiously. Man, you should have seen him jump!! He never knew what hit him!