1. The gravitational potential energy of all the water stored behind a very large dam is 1.2Ã-10^16 J, using the base of the dam as the reference point for zero PE. Imagine you could store the same amount of potential energy in a system consisting of two particles, each with a charge of 0.0020 C. How far apart should you place the charges?
2. Four charges are arranged at the corners of a rectangle as shown in the diagram on the right.
(a) What is the electric potential at the center of the rectangle?
(b) What is the electric potential there if the charges?