1. The problem statement, all variables and given/known data http://postimg.org/image/vzhqi8er5/ 2. Relevant equations 3. The attempt at a solution I understand all the calculations here - http://www.physicspages.com/2012/10/18/coaxial-cable-with-dielectric/ I have one issue that is bugging me though - if λ charge density is distributed over the inner conductor, why can it be assumed that the same -λ is distributed over the outer shell? Aren't there any bound charge densities involved here? Thank you.