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Q & A: Perpetual motion from magnets?

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Most recent answer: 04/30/2010
Q:
IF 2 magnets are fixed such that they repel each other(Means they are fixed side by side such that either of one of their same poles face each other)..My question is that if we keep magnets in such a way will they lose their magnetic strength..Why or why not...My idea of making a perpetual motion machine which generates electricity just by consuming a little energy in the begining will depend on ur answer...Plz kindly answer my question...
- Prudhvi Raj Borra (age 17)
Machilipatnam,ANdhra Pradesh,India.
A:
No, no no no.  Prudhvi, don't waste your time on this project!  Many people have spent lots of time, money and effort on such schemes.  They don't work!  There are two good reasons:  
1.  You can't win.  There is no such thing as a free lunch. First Law of  thermodynamics.  Energy is conserved.
2. Win? You must be kidding, you can't even break even.  Second Law of thermodynamics.  Any action you make tends to increase entropy.

These laws pertain to all interactions, be they mechanical, electromagnetic, chemical, etc.

LeeH

(published on 04/26/2010)

Follow-Up #1: decay of big magnets

Q:
as the previous person asked... is it possible to lose the magnetic strength of a magnet...??if so will th e magnetic field of earth and other planets reduce or not...what will be the effect of this to the expansion of the universe......... please explain. thanks...
- addi (age 17)
A:
The "permanent" magnets that we are used to do decay very slowly, as the magnetic domains in them re-align. The earth is a very different type of magnet, actively driven by circulating currents.  Those circulation patterns (whose energy comes from radioactivity in the earth's core, if I remember right) are complicated, unstable things. They weaken and flip directions, then regain strength,  on occasion. That's very different from the gradual decay of permanent magnets.

None of this plays a noticeable role in the expansion of the universe.

Mike W.

(published on 04/29/2010)

Follow-Up #2: magnetic decay

Q:
Then do the magnets lose their magnetic strength if they r suspended in such a way that they repel each other...
- Prudhvi Raj Borra (age 17)
Machilipatnam,Andhra Pradesh,India.
A:
It's true that  the  magnets will very gradually decay.  However, Lee's point about the impossibility of building a perpetual motion machine would apply even if the magnets were truly permanent.

Mike W.

(published on 04/30/2010)

Follow-up on this answer.