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Re: [Phys-l] [tap-l] Liquid helium experiments

Lowering the magnet by a thread is good - but starting with the magnet already in the dish is very dramatic also.
Watching the magnet spontaneously rise above the dish got me to thinking about a thermo question that is probably more suitable for Phys-L
So I'll cross post there as well

Consider two identical setups, each with a superconducting disk or dish and a suitable magnet for demonstrating the Meisser-whoever effect.
One experiment has the magnet placed on the disk when the cooling begins - the other has the magnet set off to the side with enough separation that its field will not significantly affect the superconductor.

Carefully measure the amount of cooling that is required for each trial to reach the final equilibrium T.

One magnet is now floating above its superconductor and the other is still just sitting there unchanged except in temperature.

Which setup required MORE cooling in order to reach the final temperature (and why - of course)

On Oct 31, 2008, at Oct 31(Fri) 11:40 , Bernard Cleyet wrote:

For a change I tried a tin watch glass, once.

bc forgot the allotrope and doesn't remember how he lowered the magnet (Pb and Sn),