# Interface dielectrics

1. Mar 3, 2008

### jesuslovesu

1. The problem statement, all variables and given/known data
A coaxial cable has a line charge running through it's center with a line charge density $$\lambda$$. There is a dielectric filled between the line charge and the first conducting shell cylinder and another dielectric between the outer cylindrical shell and the inner cylindrical shell.

2. Relevant equations
$$D_{1n} - D_{2n} = \rho_s$$

3. The attempt at a solution

My question is, in the equation to the bottom will rho have a value? Since the line charge is the only thing with direct charge on it, can I ignore the fact that there is a conductor separating the dielectrics?
I know the inner conductor will have a negative charge to counteract the field coming from the line charge, but with that equation isn't it applicable if the surface is directly charged?

so can i just say $$D_{1n} = D_{2n}$$ in this case anyway?