The plates of a parallel plate capacitor have an area of `90 cm^2`? each and are separated by 2.5 mm. The capacitor is charged by connecting it to a 400 V supply.
How much electrostatic energy is stored by the capacitor ?

Explanation

Here `A = 90 cm^2 = 90 xx 10^(-4) m^2, d = 2.5 mm = 2.5 xx 10^(-3) m and V = 400 V`
`:." Capacitance " C = (epsi_0A)/d = (8.85 xx 10^(-12) xx 90 xx 10^(-4))/(2.5 xx 10^(-3)) = 31.86 xx 10^(-12) F`
`:. " Electrostatic energy " u = 1/2 CV^2 = 1/2 xx 31.86 xx 10^(-12) xx (400)^2 = 2.55 xx 10^(-6)J`