Rod Engelsman wrote:
On Sun, Jun 1, 2008 at 11:47 PM, Robert Derman <[EMAIL PROTECTED]>
wrote:
Pat McBride wrote:
Ian;
I once learned a poem - Twinkle, twinkle, little star
Power = I sqared R
And I got beat about the head and shoulders by a math teacher, it finally
sank in that anything multiplied by zero is zero.
Soooooooooo, you must be talking about the power loss in a
superconductive
circuit???? However, you'll agree, I hope, that there'll be a small loss
in
power; otherwise we'd have the Perpetual Motion effect. There's going to
be
a small loss in power, because I don't really think there'll ever be such
a
thing as a perfect superconductor.
Superconductors are one of those odd things in physics that don't abide by
the usual rules. There is in fact NO significant loss of power from any
material when it is operating as a true superconductor. The only limitation
seems to be that superconductivity can only occur at cryogenic temperatures.
Wouldn't you still get some kind of inductive/capacitive losses? Not nearly
as much with AC but unless the current draw is dead constant you will still
have a varying current creating a magnetic field.
Rod
In the first example in this thread, "perpetual motion", an example of
this is sometimes done in a laboratory. It has little application in
the real world, for example no true perpetual motion system can ever
supply any energy to any external system, if it does, its internal
perpetual motion ceases rather quickly. The demonstration goes like
this, a superconducting circuit is powered up from an external source,
and the source is then disconnected. current continues to flow in the
superconducting circuit with no external energy input. There are no
inductive or capacitive losses simply because with no external input,
only DC can flow, therefore there is no induction, nor can anything be
capacitively coupled. In fact, the only way that this experiment can
demonstrate that there is any current flowing is by powering a magnet.
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