일반물리학 2 — Electric Potential: Problem 33

33 The particles shown in Fig. 24-38 each have charge magnitude \(q = 5.00 \text{ pC}\) and were initially infinitely far apart. To form the square with edge length \(a = 64.0 \text{ cm}\), (a) how much work must be done by an external agent, (b) how much work must be done by the electric forces, and (c) what is the potential energy of the system?