A very long, solid cylinder with radius R has positive charge uniformly distributed throughout it, with charge per unit volume p.
(a) Derive the expression for the electric field inside the volume at a distance r from the axis of the cylinder in terms of the charge density p.
(b) What is the electric field at a point outside the volume in terms of the charge per unit length" in the cylinder?
(c) Compare the answers to parts (a) and (b) for r = R.
(d) Graph the electric-field magnitude as a function of r from r = 0 to r= 3R.