# Why is a superconductor a diamagnet?

1. Nov 20, 2003

### S = k log w

Why is a superconductor a diamagnet?

2. Nov 21, 2003

### futz

Once in the superconducting state, all magnetic flux is expelled from the interior of the material. This is a result of screening currents on the surface which counteract the external field. This is similar to what happens in typical diamagnetic materials.

3. Nov 21, 2003

### QuantumNet

Warning: the following content is theoreticall

If G = 1/(8$$\pi\$$caverage), then a superconductor should be a medium in which lightspeed is the speed of light in vacuum (If a superconductor really gets lighter when it conducts than an ordinary conductor gets as Spacetravel101 claims.)

If it's true at all.

If its true, superconducting plastics should be very good materials for spaceships etc.

Maybe the even more interesting questions are:

"Why is a superconductor so black?"

Or

"Is there superconductors that reflects all light and thereby can keep it's temperature?"

Best wishes

Last edited by a moderator: Nov 25, 2003
4. Nov 21, 2003

### neutroncount

Re: Re: Why is a superconductor a diamagnet?

Hmmm...maybe you should check out nobium or titanium or tin or zinc or about any of the other metals that are superconducting. They don't look black to me. You're just talking about ceramic superconductors.

5. Nov 26, 2003

### TonyG

...minus one London penetration depth from the outer edge. Also, type II superconductors will start letting in some field in the SC state as you approach the critical point.

6. Nov 30, 2003

### Creator

Believe it or not, not all superconductors are diamagnetic!
Recent discovery:
Ferromagnetic superconductors !!

See: http://physicsweb.org/article/world/15/1/9

Yours truly,
Creator