Does inducing a current in a wire have any effect on the strength of a permanent magnet?

Question

Does inducing a current in a wire result in any changes in the strength of a permanent magnet? Specifically, what would the results of the following controlled experiment be?

You set up two alternators that each simply consist of a permanent magnet located inside a stationary loop of wire as depicted here. With the first (control) alternator, you simply rotate the magnet at a certain velocity for a short time, once per day, and measure the amount of induced current on a daily basis. With the second alternator, you hook the magnet up to your favorite (external) source of rotational motion and spin it continuously and measure the amount of induced current at the same intervals as with the control alternator.

Would the amount of current change over time (in either one)? If it would, in which direction and why? And if this is still not well-specified enough for an definite answer, what would it depend on? (how fast the magnets are rotating? what kind of circuit the wire is hooked up to? what the magnet is made out of? etc.)

@Qmechanic: It is not a duplicate. That question is about 2nd law of thermodynamics, whereas this is about electromagnetism. — Siyuan Ren, Feb 16 '12 at 08:45
It is a question about thermodynamics, whether the questioner realizes it or not. — user1631, Feb 16 '12 at 17:34

score 2 · Answer 1 · answered Feb 16 '12 at 13:06

2

Friction is a process that converts kinetic energy into heat. Its electrical equivalence is restistance; that converts electrical energy into heat. Materials with high magnetic hysteresis can convert magnetic energy into heat.

You may be confused because the usual source of magnetic energy is the physical movement of a magnet, not a loss of magnetization.

answered Feb 16 '12 at 13:06

MSalters

5,574

(This answer was in response to the earlier phrasing of the question) – MSalters Feb 17 '12 at 09:33
I shouldn't have presupposed the answer by using the term "friction". I was trying to draw a very loose analogy. – OracleOfNJ Feb 17 '12 at 14:13

Does inducing a current in a wire have any effect on the strength of a permanent magnet?

1 Answers1