The other day we were working on a problem which stated : Q charge is given to the positive plate of an isolated parallel plate capacitor of 10 μF. Calculate the potential difference betweeen the plates. Our teacher said that as the plate is isolated, Q charge will be divided between the two plates and there would be Q/2 amount of charge on each plate and hence V = Q/2C I did not understand clearly why the charge will be divided as the capacitor is isolated. It is clearly stated in the problem that Q charge is given to the +ve plate, so the same amount of -ve charge will be there on the -ve plate. Then V should be just Q/C This must be some basic concept which I got all wrong. Can someone explain this ?