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Is it possible to "extract" energy from a magnet, making it lose its magnetism? Or, to put in another way, is magnetism a form of energy? (I am not talking about potential energy in a magnetic field). Since matter is equivalent to energy, is the property of magnetism equivalent as well?

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Magnetism (as we know it in magnets) is nothing more than the alignment of a great number of atoms in similar directions so they end up producing a noticeable magnetic field. In a way you're taking advantage of the inherent kinetic energy associated with electrons orbiting a nucleus. The question would then be could we take advantage of that energy - which we really can't without disrupting the atom itself. The energy we get from atoms (fusion/fission) is from the bonds in the nucleus. The orbital speed of the electrons are defined by their orbital (energy level), and to modify it disrupts the atom's makeup.

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  • $\begingroup$ Heating a magnetized bar demagnetizes it, it shows it is in a lower energy state than the ambient temperature . It can only gain energy and be destroyed not give energy. $\endgroup$ – anna v Sep 4 '12 at 3:11
  • $\begingroup$ @annav It could still be in a metastable state, with heating required to take it over the barrier, but generally it will depend on the specifics of the thermodynamics. $\endgroup$ – Emilio Pisanty Sep 4 '12 at 13:25
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Perhaps, the following paper is relevant - "Extracting Energy from an External Magnetic Field" http://arxiv.org/abs/1208.1702

I have only quickly perused it, but it appears to provide a way to extract energy from a uniform, uni-directional magnetic field by surrounding it with a rotating cylindrical magnetic insulator.

Possibly, this approach could extract energy from a portion of a magnet's field which is small enough to be approximately uniform.

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  • $\begingroup$ How is that different from an electric generator, if movement is involved? $\endgroup$ – Tara May 1 '20 at 3:03
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You cannot extract energy from magnets. You can just disrupt the orientation of the molecules(dipoles) in the magnet(by heating or so..). The answer to the question is same as the answer to the question, "Can you remove charge of an electron??" or "Can i extract energy from the charge of an electron?". Its impossible. You can just disrupt the molecules or decompose the electron(to quarks).

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Under normal circumstances you cant extract the energy from a permanent magnet, but it is there and under special conditions you can extract that energy to do usable work. However any scenario where you extract energy from a magnet the result would be a magnet that is weaker or completely demagnetized afterwards.

Consider a hypothetical thought experiment to prove this out.. Suppose we have some magnet where its curie point, the temperature at which it will loose its magnetism, is only infinitesimally higher than the surrounding room temperature. the magnet is sitting on the floor and you tie a weight to it. An iron plate is some distance above it.

In this scenario the magnet will be pulled upward towards the plate and lift the weight upward. Then when the magnet strikes the metal plate the kinetic energy would raise the temperature of the magnet ever so slightly pushing it past its curie point, demagnetizing it and causing the weight to then drop to the floor again. The magnet will now be completely demagnetized and the energy which was stored in its magnetic field was the energy that moved the weight in the first place.

Keep in mind this is similar to just lifting the weight the same distance yourself and then dropping it. Even though gravity is what makes the weight fall it is the initial energy you put in with your arm lifting the weight that is doing the work, not gravity. In the case of the magnet that energy comes from the magnetic field and not from your arm.

Also note that if the magnet never demagnetized and the weight was only moved upward and never fell again no actual work was done because you'd have to put energy into the system to get the magnet away from the metal. Without the magnet demagnetizing it would be no different than spring where the spring itself isnt really what is doing the work as you have to put energy into it.

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