Two infinitely long cylindrical conductor whose axes coincide, have radii R1 = 6 cm and R2 = 18 cm. The cylinders oppositely charged uniformly and a linear density of 5 x 10 -8 C / m, and the charge of the cylinder of smaller radius positive. All the space between the cylindrical surfaces filled homogeneous dielectric (e = 5.0). Graphed functions f1 (r) and f2 (r).