Three equal 1.20-???C point charges are placed at the corners of an equilateral triangle whose sides are 0.500 m long. What is the potential energy of the system? (Take as zero the potential energy of the three charges when they are infinitely far apart.)

Introduction We have to calculate the total potential energy of the system. Step 1 The potential energy of two charges1q and 2 separated by a distance r is given by Since the system consists of three charges, the total potential energy will be the potential energy due to each pair of charges. Hence the total potential energy is Now Since the charges are in the corner of an equilateral triangle, the distances between each pair is charges are equal, and since the charges are also equal, the potential energy will also be equal. Hence the potential energy of each pair of charge will also be equal. Which means Therefore we have