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What would happen if... I have a round magnet with a hole in it. Then I put a magnet shaped like a nail, into the center of the other magnet? Would it float? If I spun the magnet around the inner magnet, would it spin the inner magnet?
Thank you very much.
- Matt K. Leiner (age 40)
South Lyon, MI
The inner magnet would definitely not float. A mathematical theorem due to Earnshaw proves that there\'s no way to get a magnet to float with any scheme like this. The nail will pull over to the other magnet and get stuck on it.
For your second question, let\'s assume the nail-magnet was tied on a string or something to keep it in the center, but free to rotate. What it does when the round magnet spins will then depend on how the round magnet\'s poles are configured. (I\'m assuming the poles of the nail are at its ends.) If the round magnet has, say, the south poles on its inside ring and the north poles outside, spinning it won\'t change the magnetic field and won\'t make the nail spin. If the ring\'s south pole is on one side (say left) and the north pole on the other, spinning it will make the fields spin with it. That will make the nail spin with it, at least for slow spin rates.
(published on 02/12/09)
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