What is the magnetic field around a long, current-carrying wire?

[Master J]

A long, current carrying wire has a radius R and current I.
What is the magnetic field inside, and outside the wire?


Now, if it asked what is the field a distance r from the wire, I could simply use the Law of Biot & Savart (mu.I/2.pi.r). I havn't dome electricity in a while and I am stuck on this one.

I am sure its simple, I just need a nudge.

Thanks guys.

 

[Kruum]

I'm currently using my PDA so no complex equations.But you'll need to use the Gaussian surface for magnetic field.