Earnshaw's Theorem says there is not a configuration of static magnets that will create a magnetic field with a mimimum where you can stably float another magnet. Any moving magnets will create eddy currents, and unless these are in a superconducting material there is some resistance to the currents which will cause energy loss in the system. You can create feedback systems to control an electromagnet to keep another magnet floating. I did this along time ago floating a long rectangular rare earth magnet below an electromagnet. I used a LED/photodiode combo to sense the height of the rare earth magnet and used that as an error signal to drive the electromagnet.
that's interesting info. I looked it up on Wikipedia and read a little about it and it seems to suggest that the theorem only holds for static magnets, not necessarily ones that are moving.
Comments
Earnshaw's Theorem says there is not a configuration of static magnets that will create a magnetic field with a mimimum where you can stably float another magnet. Any moving magnets will create eddy currents, and unless these are in a superconducting material there is some resistance to the currents which will cause energy loss in the system. You can create feedback systems to control an electromagnet to keep another magnet floating. I did this along time ago floating a long rectangular rare earth magnet below an electromagnet. I used a LED/photodiode combo to sense the height of the rare earth magnet and used that as an error signal to drive the electromagnet.
--Ed
http://www.physics.ucla.edu/marty/diamag/ajp601.pdf
--Ed
Hi Ed,
that's interesting info. I looked it up on Wikipedia and read a little about it and it seems to suggest that the theorem only holds for static magnets, not necessarily ones that are moving.
http://en.wikipedia.org/wiki/Earnshaw's_theorem