Physics - Capacitor Question with Solution | TestHub

Energy stored in capacitor of capacitance $C$ with voltage $V$ is, $U=\frac{1}{2}C{V}^2$ but $C=\frac{{\epsilon }_{0}A}{d},V=Ed$ where $A$ is the area of capacitor plate and $d$ is the distance of separation and $E$ is the electric field. $$\therefore U=\frac{1}{2}\frac{{\epsilon }_{0}A}{d}{E}^2{d}^2=\frac{1}{2}{\epsilon }_0{E}^{2}Ad$$