Q 1.13: Suppose the spheres A and B in Exercise 1.12 have identical sizes. A third sphere of the same size but uncharged is brought in contact with the first, then brought in contact with the second, and finally removed from both. What is the new force of repulsion between A and B?
When two spheres of same size are touched, on attaining equipotential state, the total charge of the system is equally distributed on both of them.
Therefore, (i) When uncharged third sphere,C, is touched with A, charge left on A =
and charge attained by C =
(ii) Now, Charge on B + Charge on C = + =
When touched, Charge left on B =
Therefore
Therefore,