# Electric field density at the surface of a current carring wire

## Homework Statement

Calculate the magnetic and electric energy densities at the surface of a 3.0 mm diameter copper wire carrying a 15-A current

## Homework Equations

uB=.5$$\frac{B2}{\mu0}$$
uE=.5$$\epsilon0$$E2
R=$$\rho$$(L/A)
B=($$\mu0$$I)/(2$$\pi$$r)
$$\rho$$=1.68 x 10^-8 ohm-meters

## The Attempt at a Solution

Okay, so finding the magnetic energy density isn't too difficult. My problem is with the electric energy density. I can use the area of the wire and the fact that it's copper to find the resistance and then use ohm's law to find the voltage. but then I get in this bind. E=V/d, but at the surface of the wire, d=0 so you get V/0 which kind of implies infinity and this agrees with my thoughts anyway. However, I feel like this doesn't really make any sense in terms of an electric energy density. Does some one see where the reasoning is going wrong and how I can make it right?