+2Q and -Q two pt charges are r apart. AS no external agent exists, they attract to each other and each gains +Q/2 after conduction. Like charges repel. At same distance at r, 2*k(2Q)(-Q)/r = 2*k(Q/2)sq /r + 2 KE... but what i want to know is that when is the like charges repel......just after a -Q of electrons flow from -Q to 2Q they repel...does conduction happen in a very short time to share equal charge of Q/2 before repulsion?? Or just just after a -Q of electrons flow from -Q to 2Q they repel???