Question

A parallel plate capacitor has an electrode area of 100 $m{m}^2$, with spacing of 0.1 mm between the electrodes. The dielectric between the plates is air with a permittivity of $8.85\times {10}^{-12}$F/m. The voltage on the capacitor is 100 V. The stored energy in the capacitor is

• A. 8.85 pJ
• B. 440 pJ
• C. 22.1 nJ
• D. 44.3 nJ

Answer 1

The correct option is D 44.3 nJ

Ans : (d)

$E=\frac{1}{2}QV=\frac{1}{2}C{V}^2$
=$\frac{1}{2}\times \frac{{ϵ}_{0}A}{d}\times V^2$
$=\frac{1}{2}\times \frac{8.85\times {10}^{-12}\times 100\times {10}^{-6}\times {10}^4}{{10}^{-4}}$
$=44.3$nJ