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

[John Denker <jsd@av8n.com>]

On 10/31/2008 09:07 AM, chuck britton wrote:

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

The one that requires less cooling is the one that 
did work against the gravitational field as it lifted
the magnet.

Why?  Because it did work against the gravitational 
field as it lifted the magnet.

This is perhaps marginally more obvious if you consider
the heating during the reverse process, including the
magnet plopping down imparting energy to the dish.


The effect is small and probably works better as a
Gedankenexperiment than as a classroom demo.