A positive charge +q is located at the point x = 0, y = -a, and a negative charge -q is located at the point x = 0, y = +a.
(a) Show the positions of the charges in a diagram.
(b) Derive an expression for the potential V at points on the x-axis as a function of the coordinate x. Take V to be zero at an infinite distance from the charges.
(c) Graph V at points on the x-axis as a function of x over the range from x = -40 to x = +40.
(d) What is the answer to part (b) if the two charges are interchanged so that +q is at y = +a and -q is at y = -a?