Electric charge question[Updating...] 1) I tried to do this homework, but my answer is all , of course it is not as same as this question's answer. That is my procedure: +) First, 2 charged have a same chagre Q, after these also have a same charge q=(Q-Q'). +) F'/F=[(Q-Q')/Q]^2. +) I substituting all answer, and it is correct all, i can have 1 Q'. Why the answer is C. 2) F=Q.q/4piE(a^2+d^2) F max when a^2+d^2 min=> d^2 min when d=0 why the answer is E, i think a true answer is A 3) Following my textbook: it is also existing an electric field inside a insulator. So the answer E is not correct, because it still have Electric force. I think A is true. Am I right?