Question

An infinitely long line of charge has linear charge density ë. Find the energy density of the electric field at a point a radial distance r from the wire. (Use the following as necessary:
å0, ë, r.)

Answer 1

Do you how to use Gauss law to determine the electric Field E at some point r away from the line?

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elelin.html

Then Energy density is E/volume, and that works out to be 1/2 epsilonnaught*E^2