When you introduce the magnet to the presence of the superconductor, currents are induced in the superconductor that cause the magnetic field to exactly cancel at the surface of the superconductor such that there is no penetration of the magnetic field into the superconductor. However, this induction of a new current is of non-zero frequency, and hence these non-zero frequency current components will experience a finite resistance.
On Sat, Nov 14, 2015 at 3:47 PM, Eric Walker <[email protected]> wrote: > On Sat, Nov 14, 2015 at 4:26 PM, David Roberson <[email protected]> > wrote: > > So, I would expect to see the falling velocity of the magnet to become >> less and less as the conductor used for the pipe become less resistive. >> But, the geometry is also going to enter into the equation. > > > Let's assume a geometry favorable to the suspension of the heavy permanent > magnet for indefinite duration. > > If we assume that the pipe diameter is sufficiently small then it would >> make sense to assume that the magnet would be suspended at zero velocity if >> placed within a super conducting pipe. > > > It's clear that with sufficient current in the superconductor, the heavy > magnet will just sit there, with the force of gravity counterbalanced by > the magnetic field that is induced. My question is whether the system is a > stable one, or whether there's a gradual decrease in the current as a > function of time. > > In one scenario, the heavy magnet is suspended in the superconductor > indefinitely. In another scenario it is suspended there for a long time, > until the current drops below a critical threshold, at which point it will > move down a little, and so on, until it falls through. > > Just so I understand your argument -- is your understanding that the force > of gravity does not indirectly counteract and do work against the current > circulating in the superconductor as the heavy magnet is suspended there? > > Eric > >
