1. The problem statement, all variables and given/known data An infinite line of charge with linear density λ1 = 6.7 μC/m is positioned along the axis of a thick insulating shell of inner radius a = 2.4 cm and outer radius b = 4.7 cm. The insulating shell is uniformly charged with a volume density of ρ = -722 μC/m3. What is λ2, the linear charge density of the insulating shell? 2. Relevant equations (Vouter shell-Vinner shell)*ρ <-- current one I'm using, but I could be wrong. 3. The attempt at a solution My approach has been to find a bridge between the two densities by relating the volume to the length, but in every attempt I've made I've run into the problem of what to do about the length variable, as the shell is infinite. This is a gauss's law problem, so I've also tried using that to get rid of length variable - however I realized I didn't have the E-field. With the current equation I'm using, I've again run into not knowing what to do about the length of the cylindrical shell. ETA - Okay, I've now tried this: ρ=Q/(2pi(b2-a2)L) and Q=ρ*V=λ*L So, λ*L=(2pi(b2-a2)L)*ρ, and the lengths will cancel λ=(2pi(b2-a2))*ρ Answer is wrong though.