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Putting aside any energy generating schemes that would break the laws of thermodynamics, is it possible or is there a motor which generates power using a permanent magnet? So that the energy wouldn’t be coming from nothing but from the atoms in the magnet being misaligned.

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The idea of a "magnetic motor" pops up on the interwebs almost weekly, accompanied often with youtube clips of the device "actually running", conspiracy theories about the idea being suppressed by government agents, and so forth. Too bad it is impossible.

The best disproof I have read about the fundamental idea of building a motor out of permanent magnets with no electrical power input runs like this- and please, I invite the experts here to check the reasoning to make sure I am remembering it correctly:

The field created by any magnet (except a monopole, which I will omit from the discussion) exhibits a property called "divergence". The divergence of the magnetic field happens to be zero, which is another way of expressing the fact that every field line emerging from one pole of the magnet loops around and ends on the other pole of the magnet. The argument goes that if the divergence of the field is zero, then there is no way ever for a magnet to be cleverly smuggled into the proximity of another magnet in such a manner that the two magnets will magically ignore one another- until at some point they wake up and suddenly repel each other, and in so doing insinuate yet another magnet into position and repeat the process, etc., etc. and thereby create a motor that performs work with no power input.

This fact does not stop people from tinkering and dinkering with fistfuls of artfully contrived links, levers, cams and gearwheels with precisely-machined magnets stuck in strategic locations throughout, in the mistaken belief that a "free-energy" or "over-unity" perpetual motion machine is just one experiment away from reality.

It also does not stop fraudsters from duping venture capitalists and even governments into believing that their free energy motor is real and worth spending millions of dollars developing. This took place in Europe not too long ago, with the whole shebang going down to wreckage and ruin, winning prison sentences for the perps.

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In my opinion the answer is: energy is conserved, if kinetic energy is extacted using a permanent magnet, it will be at the expense of demagnitization of the magnet. Here is a link with some estimates of the amount of energy stored in a permanent magnet.

There is energy stored in a permanent magnet which slowly becomes demagnetized if it is used for moving masses.

A magnetic circuit-based approach to deriving stored energy provides an intuitive understanding of stored energy in permanent magnets. The resulting energy expression is also consistent with all granularities of analysis, from magnetic circuits to 3D finite elements calculations.

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  • $\begingroup$ It was not me downvoting this answer. But I would say that when a permanent magnet lifts a piece of iron, that the energy comes from the magnetic field (from the volume in between). I agree though that the energy involved in demagnetizing a permanent magnet is small - it is the coercivity times the magnetization. $\endgroup$
    – user137289
    Jan 26, 2018 at 9:56
  • $\begingroup$ @Pieter well, any perpetual motion machine will demagnetize the permanent magnet eventually. $\endgroup$
    – anna v
    Jan 26, 2018 at 12:46
  • $\begingroup$ So there because there is energy stored in a static magnetic field, you could in principle extract that energy. $\endgroup$
    – Tom
    Jan 26, 2018 at 13:17
  • $\begingroup$ @Tom yes, but in the end you would be left with diminishing returns and without a permanent magnet. $\endgroup$
    – anna v
    Jan 26, 2018 at 13:43
  • $\begingroup$ anna v, do you know if the divergence argument i used above is valid? -Niels $\endgroup$ Jan 26, 2018 at 16:39

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