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Q & A: magnetic poles and levitation

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Most recent answer: 10/22/2007
Q:
i know it is possible to make objects levetate with magnets, but is there a way to keep them stable so they will stay in place in the air? And also i was wondering if there are any magnets that only have a negative or positive charge or if there are any uneven magnets with one pole larger than the other.
- Michael (age 15)
Corpus Christi, TX
A:
There's a theorem that you can't get stable levitation with any classical collection of magnets, charges, gravity, etc. You can get stability only if you allow forces that classical mechanics can't explain. These include contact forces between objects, but I don't think that's what you're interested in. It's no surprise that you can support something by putting it on a table.
Another type of force that doesn't make classical sense is diamagnetism- the tendency of some objects to be repelled by magnetic fields. Most of us are weakly diamagnetic. Diamagnetism allows stable levitation. I've seen photos of very tiny frogs levitated stably by strong magnetic fields, but that's impractical for larger objects. However, many superconductors are very strong diamagnets, avoiding magnetic fields altogether. Superconductors can indeed be stably levitated, as can magnets near superconductors.

No one has ever found anything with a net magnetic charge, where the Northness and Southness don't exactly cancel. We have a name for these hypothetical objects, if they ever show up: magnetic monopoles. Some theories of the early universe say that there should be a very small number of these monopoles around.

Mike W.

(published on 10/22/2007)

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