Stable levitation of one magnet by another with no energy input is usually prohibited by Earnshaw’s theorem. However, the introduction of diamagnetic material at special locations can stabilize such levitation. A magnet can even be stably suspended between (diamagnetic) fingertips. A very simple, surprisingly stable room temperature magnet levitation device is described that works without superconductors and requires absolutely no energy input. Our theory derives the magnetic field conditions necessary for stable levitation in these cases and predicts experimental measurements of the forces remarkably well. New levitation configurations are described which can be stabilized with hollow cylinders of diamagnetic material. Measurements are presented of the diamagnetic properties of several samples of bismuth and graphite.

Topics
Diamagnetic materials, Superconductors, Carbon based materials, Chemical elements
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© 2001 American Association of Physics Teachers.
2001
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