# Difference between Perfect Diamagnetism and Superconductors

1. Nov 11, 2008

### Hells_Kitchen

Could someone please explain the difference between Perfect Diamagnetism and Superconductors in terms of the Meissner Effect and the magnetic field passing through an element of the sort.

Under low temperatures in perfect diamagnetic materials if there is a magnetic field it remains the same even when the resistance becomes 0 while for superconductors under low temperatures when they reach the superconducting point (low enough temp.) they exclude any external magnetic field that might be passing through them. Why is this the case? I know this is explained through the Meissner Effect but I do not really understand the concept and theory behind it.

Thanks,
HK

2. Nov 12, 2008

### granpa

Re: Superconductors.

diamagnetic materials exclude magnetic fields from there interiors just as paramagnetic materials attract them. diamagnetism is associated with lone pairs of electrons just as superconductivity is associated with cooper pairs.

3. Nov 12, 2008

### Hells_Kitchen

Re: Superconductors.

Thanks for your answer but could you elaborate a little more on perfect diamagnetism and the Meissner effect for superconductors.

Thanks,
HK

4. Nov 12, 2008

### ZapperZ

Staff Emeritus
Re: Superconductors.

Not sure if you want simply a hand-waving argument, or a detailed derivation. Still, check out the hyperphysics webpage

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

If you click on the link for the London equation, you'll get one of the derivation of the Meissner effect.

Zz.

5. Nov 12, 2008

### Hells_Kitchen

Re: Superconductors.

That seems like a very nice and elegant proof, however, I would appreciate a conceptual description (or hand-waving argument like you said) since this is a presantation topic for my E&M physics course.

Thanks,
HK

6. Nov 12, 2008

### ZapperZ

Staff Emeritus
Re: Superconductors.

Then put the mathematics into words, introduce a few vague analogies, and viola! You have a hand-waving argument.

Zz.