Halliday, Resnick & Walker — Coulomb's Law: Problem 37

37 Of the charge \(Q\) initially on a tiny sphere, a portion \(q\) is to be transferred to a second, nearby sphere. Both spheres can be treated as particles and are fixed with a certain separation. (a) For what value of \(q/Q\) will the electrostatic force between the two spheres be maximized? What are the (b) smaller and (c) larger values of \(q/Q\) that give a force magnitude that is 75% of that maximum?