[SOLVED] Electric field around cylinder 1. The problem statement, all variables and given/known data An infinitely long cylinder with r = 4.0 cm has a uniform charge density of 200 nC/m^3. What is the electric field 3.9 cm away from the axis? 3. The attempt at a solution The first thing I thought is that the field has got to be 0 since all the charge will be on the surface of the cylinder. But maybe this applies only to spheres? Anyway, I calculated the charge per meter: 1.01 nC/m. Then I used Gauss law: Q/l = e0E*2*pi*r, which yields E = (Q/l)/(2*pi*r) = 0.47 kN/C Is this correct?