Figure 2-18 (a) Symmetrically located line charge elements on a cylinder with uniformly distributed surface charge show that the electric field is purely radial. (6) Gauu's law applied to concentric cylindrical "surfaces shows that the field inside the surface charged cylinder is zero while outside it is the same as if all the charge per unit length 0"0 2."a were concentrated at the origin as a line charge. (e) In addition to using the surfaces of (6 ) with Gauss's law for a cylinder of volume charge, we can also sum the contributions from incremental hollow cylinders of surface charge.