John, Do you know where the energy goes that is put into the system of magnet 
and disk due to the movement I mentioned?  I assume it had to become heat 
energy in one of the two parts of the system.  Is it the magnet or the disk?  
My first thought is that the magnet is the sink.

Dave


>>>>From: John Berry <aethe...@gmail.com>
Sent: Tue, Oct 18, 2011 5:35 pm


All this talk of pinning is just fine, but all of this is nicely predicted by 
the basic laws of electrical induction and the zero resistivity offered by a 
superconductor, you would expect repulsion or attraction to occur.


Now if this were done in a Vacuum then there would be zero air friction 
naturally, the superconductor would be easier to keep cold and it could just go 
on and on and on and on and on.


On Wed, Oct 19, 2011 at 10:18 AM, Harry Veeder <hveeder...@gmail.com> wrote:



On Tue, Oct 18, 2011 at 1:15 AM, David Roberson <dlrober...@aol.com> wrote:
>
>>From: Harry Veeder hveeder...@gmail.com
>
>>If the "law of inertia" is universally true, some sort of centripetal
>>force is required to keep the disc revolving in a circle as it moves
>>above the magnets. I can vaguely grasp how the phenomena of locking
>>preserves the tilt of the disc, but how does locking bring about the
>>necessary centripetal force?
>
>>Harry
> It is a beautiful presentation and raises several good questions such as:
>
> It appears to take force to get the disk to move close to the supporting
> magnetic structure.  This suggests that energy has to be applied to the
> system as the force occurs over a finite distance.  Then if the disk is
> removed, force again must be applied in the opposite direction.  More energy
> is absorbed by the system of magnet and disk.  Now, where does the energy go
> which is supplied?  I understand that a superconductor does not allow
> resistive loss from current flow so I suspect magnet must gain energy.  Does
> it actually become warmer as a result of this operation?
>
> Dave



Hmmm it obvious now. Clearly a superconductor can be made to exhibit
both attractive and replusive behaviour simultaneously through the
effect of "flux trapping". The attractive behaviour is what keeps the
disc on the tract. However, when I took undergraduate physics 25 only
the meissner effect which results in repulsion was mentioned.
 After doing some on line research I found out it was considerably
more difficult to produce flux trapping with the superconductors that
were available in the 80's. I guess the impractical nature of
demonstrating fluxtrapping meant the phenomena need not be mentioned.


Harry







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