Magnets and Energy
Most recent answer: 01/07/2017
- Mike (age 49)
We've addressed this question numerous times before: http://van.physics.illinois.edu/qa/listing.php?id=339. The magnet doesn't have to supply energy any more than your car engine has to supply energy to keep the car parked on a sloping street.
But what about the electromagnet? Inside the electromagnet, the magnetism comes from electrical currents. If it's not a superconductor, those currents of moving electrons run into electrical resistance, friction with the non-moving atomic nuclei. So their energy is turned into heat, just like electrical energy in a light bulb or an electric blanket turns to heat.
Inside the permanent magnet the magnetism comes from the permanent internal spin property of each electron, not from the sort of large-scale currents that can run down. The way a "permanent" magnet can run down is if the spins in different electrons get out of line with each other. That will happen if it gets too hot.
(published on 01/07/2017)