A parallel plate capacitor is connected to a battery that maintains a constant potential difference.
If the sepration between the plates is doubled. The electrical energy stored on the capacitor change. It will be cut in half.
If the battery remains connected, the potential difference between the plates remains constant.
In this case the energy is inversely proportional to the separation between the plates.
Hence, if the distance between the plates is doubled enrgy becomes halved.
Thus, the given option (3) is correct.
