Current in Superconductors

Thank you... and to ease your mind it wasn't an over-unity question... I wasn't imagining you would get energy out etc - just a curiosity that has bugged me!

So am I right in saying (as an analogy I can get my head around) that in principle it's a bit like say a cymbal (like on a drum kit) in a vacuum that is made of a special material that has no friction between the atoms... hit it, and theoretically it vibrates forever.

Yes.

If you are going to join the ends, then they must previously NOT have been connected.

I assume you are talking about some form of loop, so the ends are near but not connected.

If the ends are not connected, how can there already be a current?

Ok - good point - I guess I meant if you have a generator in the loop providing a current, then you switch off the generator and instantaneously complete the superconducting circuit.

There is no need to connect it suddenly. If I understand it correctly, you simply fabricate the complete loop, cool it to the superconducting temperature, then induce a current in it with a magnetic pulse. The source loop or coil and the superconducting loop constitute a transformer.

Once the current has been induced in the superconducting coil, it will continue; It's analogous to placing a magnetizable bar in a coil of wire, and momentarily sending a current through the coil; the bar will be 'permanently' magnetized, which is equivalent to saying there are 'permanent' currents circulating within the bar.

http://hyperphysics.phy-astr.gsu.edu/hbase/solids/scond.html

This link may be of interest.

Nothing, It is still a one piece conductor no matter what shape it is.

The charge should still remain unless your handling of it causes it to discharge. Since the nobility of the conductor is uniform, there is no difference in potential to align polarity from one end to the other. If you don't think it is, prove it....

In theory the circuit should self sustain, i.e. perpertual motion. However, due to natural decay of atoms within the insulation material the circuit would eventually stop. In order to mainatain the conductor at a zero resistance, it would require far greater energy and would have to remain constant. Any change in the zero resistance of the conductor, will decay the circuit. And, if the zero resistance of the conductor altered to above zero resistance, several times, over the course of a few days or weeks the circuit would eventual be at zero current. (Due to changes in the conductor and insulation creating leakage). See 'Meissnner Effects for super conductors'. I stand corrected on this.