# Superconductor: Magnetic Field Strength VS distance

Gold Member
Hi all,

Does anyone know how the magnetic field strength of a superconductor varies as distance from the outside of the superconductor?

Aside from a superconductor being able to creates a stronger magnetic field than a regular dipole, does the strength still go down as 1/r^2 or does it decrease by some other way?

Any webpages that show such graphs or formulas are helpful, if the superconductor B-field does decreases differently than normal magnets.

ZapperZ
Staff Emeritus
Hi all,

Does anyone know how the magnetic field strength of a superconductor varies as distance from the outside of the superconductor?

Aside from a superconductor being able to creates a stronger magnetic field than a regular dipole, does the strength still go down as 1/r^2 or does it decrease by some other way?

Any webpages that show such graphs or formulas are helpful, if the superconductor B-field does decreases differently than normal magnets.

I'm a bit confused here.

The magnetic field that is produced by a superconductor has no strange, unusual properties. Maxwell equations work perfectly well. It has a stronger field because it has a bigger current! That's it. There isn't any magic.

Zz.

Gold Member
I just wasn't sure if superconductors went as something different as 1/r^2. For example, a sphere of rotating charge produces a magnetic field that falls off as 1/r^3 when you get far from it, and I know there are magnetic fields that have 1/r^4 terms when you get far from the magnet. The magnetic field of a solenoid is constant--it never gets any weaker inside the coil no matter where you go. Not even talking about superconductors, regular magnets can have different math behaviors as you get far from them, depending on the configurations of the currents or atoms that make them. I just wasn't sure if superconductors followed different power laws as one moved away from them. I guess they are just like any other magnets, just stronger. If I had a superconducting magnet and moved away, it would be stronger than a regular magnet, but still diminish by 1/r^2 as you moved away from it.

There is no innate difference about the magnetic field of a superconductor. The differences you describe arise purely from geometric considerations. The only practical difference that you need to know about a superconductor is that its resistivity falls to zero when the material temperature drops below some critical value. That's it.

Gold Member
I thought so, but just wasn't sure. I got it. All good. Thanks for you help everyone!