The energy required to charge a parallel plate condenser of plate separation d and plate area of cross - section A such that the uniform electric field betwen the plates is E, is :

Question

$\begin {array} {1 1} (1)\;\large\frac{1}{2} \in_0E^2\: Ad & \quad (2)\;\large\frac{1}{2} \in_0E^2/A.d \\ (3)\;\in_0E^2/Ad & \quad (4)\;\in_0E^2Ad \end {array}$