- #1

FoxBox

- 10

- 0

I'd like to calculate the inductance of a straight current carrying wire per unit length of wire.

The wire has radius R. Assume the current is uniformly distributed over the wire's cross section.

My approach:

The magnetic energy density at every point is given by u = B^2 / (2 * mu-nought).

Knowing the total energy per unit length we can calculate the inductance per unit length of the wire:

U = .5 * L * i^2

But when I calculate it (integral breaks in two pieces: B inside and outside the wire), I find this energy per unit length is +infinity ! This off course, isn't possible.

Now, I have two questions:

1) what am I doing wrong using this approach?

Some sites talk about "internal induction". They only calculate the energy associated with the magnetic field INSIDE the wire. Has it something to do with that?

2) what EMF is causing this inductance?

Greetings to you,

FoxBox