# Eddy currents in a superconductor

Just had a lesson we just had our teacher introduced the concept of eddy currents, and showed us how a magnet moves slowly through a metal tube due to the opposite generated magnetic field.

If you dropped a magnet through a superconductor then, would the magnet just float there? (Because the superconductor's eddy currents would be exactly the right amount and would not decrease due to internal resistance)?

Thanks!

• There are many magnetic levitation videos and here is one which is slightly different. youtube.com/watch?v=zPqEEZa2Gis May 12, 2016 at 9:02

Yes, you are correct. The magnet would just float, perhaps even before entering the tube. You anticipated correctly that the strength and lack of dissipation of the eddy currents keep the magnet in place. This is well illustrated in a clip about levitating superconductors.

• Wouldn't that mean that if you tried to move that magnet, the repulsive force would be the same, so you couldn't move it? Where's the limit. Apr 4, 2017 at 13:20
• Yes, there is general resistance to moving the magnet in the vicinity of the superconductor and there is a limit to this force. The limit probably depends on the maximum current density that the superconductor can carry before losing its superconductivity. Jun 18, 2017 at 2:00