Magnet basics

Is there free energy in magnets?

Every once in a while I come across a paper or article while surfing the web which claims that it is possible to tap into the free energy which is available from the earth's magnetism, or from some other magnet.

This all sounds great, but there is the problem that energy is never free but always comes with a price.

Sure, in order to magnetize a magnet, energy needs to be put into it.  This is done when a large current is pulsed through a coil in which the material to be magnetized sits.  The result of this pulse of current, which contains a certain amount of energy that can be measured, is to enlarge the magnetic domains which are parallel with the magnetic field within the material being magnetized.  What will cause the magnetic domains to shrink again?  Three things,
1.  An increase in the temperature of the magnet.
2.  An external demagnetizing magnetic field.
3.  Physically shaking or striking the magnet.

Each of these, as you can see, requires that energy be spent (heat, magnetic field, motion).  None of these allows for a way to capture energy released by the decrease in the overall magnetic field.  (Adiabatic cooling does capture some of the heat energy due to the overall magnetic domains becoming random, but it requires energy to be put into the material first.) Also, there are always energy losses in every circuit (in various forms of heat energy, sound energy, mechanical energy, chemical energy, electrical energy, etc).

A keyword often used by those who think they have found the secret to free energy is:   over-unity.  What they mean by this is that the ratio of the energy output to the energy input is greater than 1 (more energy comes out than goes in).  It sounds great, but the physics is poor.  When making energy measurements, there are a number of errors that can be made, often unwittingly, that falsely indicate over-unity is possible.  In reality, it isn't.

I have also heard of a scheme that changes some of the matter into energy (using E=mc^2) by actually taking the copper atoms and converting them into energy.  If that inventor is able to accomplish this, great.  But, this would not fall into the "over-unit" group of inventions.  Eventually, the fuel runs out.  A sun or a star is good at doing this.  They have the advantage of high pressures and high temperatures and large mass.  But they also will run out of fuel.

Here's are great articles that explain what is often neglected by those proposing free energy devices:
An article by Peter Campbell titled, "Comments on Energy Stored in Permanent Magnets" from IEEE Transactions on Magnetics, Vol 36, No 1, Jan 2000
http://www.lhup.edu/~dsimanek/museum/unwork.htm for discussions on perpetual motion machines

This Q&A was found at:
http://www.physlink.com/Education/AskExperts/ae354.cfm for a discussion on how the energy of a magnet changes

Question

Since magnetic forces can do no work, what force IS doing the work when a bar magnet causes a paper clip to jump off a table and stick to the magnet?

The original assumption that a magnetic field can do no work is incorrect. A magnetic field has an energy density that is equal to the magnetic induction (B) squared divided by twice the permeability (mu sub zero). If you were to sum (integrate) this energy of the magnet over all of its field before it picked up the paper clip and compared it to the same sum after you picked up the paper clip, you would discover that there was a loss of field energy. The paper clip has in effect 'shorted out some lines of magnetic flux'.

How much energy was lost? If you took hold of the paper clip and pulled it out to such a distance that the magnetic pull was insignificant, the work you did in this process would exactly equal the amount of energy lost when the clip was on the face of the magnet. When you picked up the clip with the magnet the clip was accelerated toward the magnet acquiring kinetic energy. This kinetic energy will equal, ignoring air drag, the loss of magnetic energy in the field. This kinetic energy will be dissipated in the form of heat on impact of the clip with the magnet.

For further understanding of the energy in a magnetic field, you may want to study magnetic fields in solenoids. See the Reference below.

Physics, Volume 2 by Halliday and Resnick
Answered by: Robert Gardner, M.S., Retired Physicist

Have you wondered just how much energy is actually stored in the permanent magnet's magnetic field?  Check this out!

In summary, there is no way to obtain free energy with any kind of combination of wires or magnets or switches (commutators, diodes, etc).