Chapter 22, Problem 65P

In Fig. 22-64a, a particle of charge +Q produces an electric field of magnitude E_part at point P, at distance R from the particle. In Fig. 22-64b, that same amount of charge is spread uniformly along a circular arc that has radius R and subtends an angle θ. The charge on the arc produces an electric field of magnitude E_arc at its center of curvature P. For what value of θ does E_arc = 0.500 E_part? (Hint: You will probably resort to a graphical solution.)

Figure 22-64 Problem 65.