1. The problem statement, all variables and given/known data: the excess(equal in number) of electrons that must be placed on each of two small spheres spaced 3 cm apart, with force of repulsion between the spheres to be 10^-19N, is...? 3. The attempt at a solution: since, f=kq^2/r^2. ive calculated q from here which is 1x10^-16N.. then used, q=ne.. from here n becomes 625 electrons. but answer in my book is 25 electrons.can someone point out my mistake?