1. Two long charged, concentric cylinders have radii of 3.0 and 6.0 cm. The charge per unit length is 5.0 x 10-6 C/m on the inner cylinder and -7.0 x 10-6 on the outer cylinder. Find the electric field at (a) r = 3.0 cm and (b) r = 8.0 cm, where r is the radial distance from the common central axis. 2. Relevant equations ε0 ∮EdA = qenc λ= Q/L 3. The attempt at a solution EA = qenc/ε0 E = λL/ π r2 ε0 From here, I don't know what to do with L. The height of the cylinder should be irrelevant, right? I have another similar question using ρ and volume, leaving me with a height in the formula for the volume that I don't know what to do with. Thanks.