When putting two small magnets side by side they move towards eachother. Where does that energy come from? Remeber that the magnetic fields do not perfrom the work. Thanks
2007-12-11 01:29:35 · 4 answers · asked by Brian 6 in Science & Mathematics ➔ Physics
That energy came from initially separating them - even if you have to go back to the Big Bang for when they were together.
2007-12-11 01:39:33 · answer #1 · answered by Gary H 6 · 1⤊ 0⤋
These other answers are mumbo-jumbo, I'm afraid. But magnetic fields and fluxes are hard to understand.
The energy stored in a permanent magnet is the energy stored in the magnet's internal reluctance. So answer 1 above is along the right lines in saying that energy is stored within the material. Imagine making a permanent magnet by applying an external magnetic field to a magnetic material. As the field is removed, hysteresis mechanisms within the material maintain a non-zero flux density, and permanent magnet is made. The permanent magnet ends up with a positive flux density, and a field strength that is negative (the other direction) comared to the magentising field.
B = + ve
H = - ve
Energy stored within the permanent magnet, E is
E = 1/2 * R * Phi square
where R is the magnet's reluctance, and Phi is the flux density.
and from this, the Energy Density, e
e = 1/2 * mu * H squared
where mu is the permeability of the magnet (usually close to Mu0, the permeability of free space), and H is the magnetic field intensity.
But again, the energy is stored within the permanent magnet. You can measure the amount by doing mechanical work experiments - bring in a iron plate and attach the magnet to it so it cant do any more work, and the magentic field drops to zero. Now measure the work done (force x distance) in separating the magnet and plate.
2007-12-11 02:22:51 · answer #2 · answered by Anonymous · 0⤊ 1⤋
(got this from another answer) There is a very small amount of energy in all matter on a quantum level. In a magnet the atoms are all lined up so this small force is magnified. The quantum energy of the electrons lined up prvides the energy. Remember that enectrons are the only subatomic particles with inherent motion. Motion equals energy
If you magnetize a needle (two wires going to car battery method), it is magnetized, Then to demagnetize it drop it on concrete a few times. I think that's all that's needed.
2007-12-11 01:35:45 · answer #3 · answered by Bones 2 · 0⤊ 2⤋
When you pull the 2 magnets apart you are adding a type of potential energy. Then when you allow them to come back together that energy is expended.
2007-12-11 01:38:18 · answer #4 · answered by Tim C 7 · 0⤊ 0⤋