1. The problem statement, all variables and given/known data A non-conducting, infinitely long, cylindrical sheath has inner radius r=10 m, outer radius r=15 m and a uniform charge density of 9 nC/m^3 spread throughout the sheath. Magnitude of electric field at r=5, r=12, r=17? 2. Relevant equations Q=rho(Volume) and phi=EA therefore phi=E(2pi(R)length) phi=Q/epsilon_0 3. The attempt at a solution At r=5, Electric field=0 At r=12, phi=Q/epsilon_0, so E(2pi(R)length)=Q/epsilon_0 I just don't know what Q will be. The same for r=17, I don't know how to find Q.