# Self Inductance

1. Mar 2, 2009

### captain.joco

1. The problem statement, all variables and given/known data
Show that the self-inductance per unit length of a wire of radius R carrying a uniform current density inside, the current returning along the surface of the wire is μ0/8π.

3. The attempt at a solution
I thought that it might be simpler to calculate the self inductance by 1st calculating the energy stored in the magnetic field round the wire.
So,

W = (LI^2)/2 = (1/2μ) ∫ B^2 dV.

I guess the question implies that the wire forms a circle ( since radius is mentioned ). Now I have problems finding B. I can find B easily in the center of the circle or on axis through the center, but surely I need to find it outside of the circle as well... how do I proceede from here, or do I need to employ a different method.
Thanks is advance!
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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