Example 2: Work and Electric Potential Energy
Two-point charges are located on the x-axis, 𝑞1 = −𝑒 at 𝑥 = 0 and
𝑞2 = +𝑒 at 𝑥 = 𝑎.
(a) Find the work that must be done by an external force to bring a third point
charge 𝑞3 = +𝑒 from infinity to 𝑥 = 2𝑎 .
(b) Find the total potential energy of the system of three charges.