Walker, Halliday & Resnick — Electric Potential: Problem 61

61 (a) In Fig. 24-47, what is the net electric potential at the origin due to the circular arc of charge \( Q_1 = +7.21 \text{ pC} \) and the two particles of charges \( Q_2 = 4.00 Q_1 \) and \( Q_3 = -2.00 Q_1 \)? The arc's center of curvature is at the origin and its radius is \( R = 2.00 \text{ m} \); the angle indicated is \( \theta = 35.0^\circ \). (b) What is the net electric potential at the origin if both \( Q_1 \) and \( R \) are doubled?