In the textbook, it is shown in Example 21.11 Section 21.5 that the electric field due to a line of charge is perpendicular to the line and has a magnitude of 1/2πε₀r. Consider an imaginary cylinder with a radius of 0.220 and a length of 0.425. This cylinder has an infinite line of positive charge running along its axis. The charge per unit length on the cylinder is 520 C/m.