# If I have electric current going through a superconductor and cut off the power in what fraction of a second will the electrons stop moving?

If I have electric current going through a superconductor and instantly cut off the power supply(rendering the circuit open, and not at all closed), In what tiny fraction of a second will the flowing electrons come to a complete stop? I know it must be a very small order of magnitude but I'm curious how small. I know it probably varies so I just need a general idea, If that's too vague, well then how about how fast it would stop if I gave it for example, 1 volt, and 1 amp and If an example substance is needed, then pick one, like niobium for instance, I'm just trying to get a general idea of the ranges of on how fast the current comes to a stop, in superconductors when you break the circuit.

• If we assume the superconducting circuit is closed (say.. a loop), since a superconductor offers no resistance to the flow of electrons, then, theoretically, the current will never stop. – Physicist137 Nov 3 '17 at 14:41
• And the electrons don't come to a stop. Net movement (current flow) may cease, but the electrons keep moving. – Jon Custer Nov 3 '17 at 15:00
• Every wire is an inductor and the rate of change of current in the wire is related to the voltage along the length of the wire by a property called "inductance". The inductance value is going to be different for different wires---determined mostly by geometry. It will be different for different wires. – Solomon Slow Nov 3 '17 at 16:20
• when I said cutting off the power supply, I meant rendering the circuit open, and not at all closed... I meant instantly no longer having a complete circuit – baconcat Nov 3 '17 at 16:54
• Do you have inductance in a superconductor? How do the electrons feel the B field if it doesn't penetrate the SC ? – Martin Beckett Nov 4 '17 at 1:54