Superconductors and best conductors

[fisico30]

Hello Forum

gold, silver, copper are the best electrical conductors are room temperature. But they cannot be superconductors: there is no finite, low critical temperature at which they become superconductors...

But what if we could bring their temperature to 0 kelvin? I believe that all metals become superconductors (R=0) at o kelvin, correct?
All materials? Even insulators, can be become superconductors at 0 k?

thanks
fisico30

 

[ZapperZ]

Hello Forum

gold, silver, copper are the best electrical conductors are room temperature. But they cannot be superconductors: there is no finite, low critical temperature at which they become superconductors...

But what if we could bring their temperature to 0 kelvin? I believe that all metals become superconductors (R=0) at o kelvin, correct?
All materials? Even insulators, can be become superconductors at 0 k?

thanks
fisico30

There's a difference between a metal having "zero" resistivity and a superconductor. A superconductor has a stricter criteria, and, it is a "phase transition".

One needs to look at the Meissner effect, and the different between a diamagnet and perfect diamagnet. It is clearly manifested when cooling in a magnetic field.

BTW, most metals do not have zero resistance at T=0. There is something called residual resistivity that starts to creep up as one gets very close to 0K.

Zz.

 

[fisico30]

Ok, thanks, I see.

So silver does not have a critical temperature and it may not even have zero resistivity at T=0 K...

As far as the current flowing in superconductors go: I think the current can only be a surface current, regardless of it being DC or AC...
Is that correct? If so, why?
thanks
fisico30