Consider a parallel-plate capacitor, each of the plates has an area S and they are separated by a distance d. Assume that plates 1 and 2 carry charges +Q and -Q uniformly distributed on them. The energy stored in the capacitor is

Parallel plate capacitor: A parallel plate capacitor is a type of capacitor that consist of two parallel and closely spaced conductive plates seperated by a dielectric material.

Energy stored in capacitor = \(\frac{1}{2}CV^2 \)

Where, Q is the charge on the capacitor.

V is voltage.

C is capacitance.

= \(\frac{1}{2}C(\frac{Q}{C})^2\)

=\(\frac{1}{2C}Q^2\)

Here, option 3 is correct.