In the demonstration where a magnet is slid down a tube of conductive material, the magnet drops at a slowed and constant rate due to eddy current braking effect.

What factors will contribute to the intensity of this braking effect? I suppose one factor would be the strength of the magnet. However, it seems like the conductivity of the tube is not simple proportional to the braking effect, since I have read in other questions that a superconductor would in fact offer no resistance in such a scenario. (I might be wrong on that, but I hope you do not dwell on it too much in your answer/comment.)


1 Answer 1




where $V$ is the volume of the tube within the magnetic field $B$, $v$ is the velocity and $σ$ is the conductivity of the tube.

For a tube, you can consider $V$ to be equal to a section of tube roughly equal to the length of the magnet, as long as the inner and outer radii of the tube are both not much bigger than the magnet.


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