Consider the arrangement of point charges described in Exercise 23.25.
(a) Derive an expression for the potential V at points on the y-axis as a function of the coordinate y. Take V to be zero at an infinite distance from the charges.
(b) At which positions on the y-axis is V = 0?
(c) Graph Vat points on the y-axis as a function of y in the range from y = -2a to y = +20.
(d)What does the answer to part (a) become when y » a? Explain why this result is obtained.