Question

A parallel plate capacitor having a plate separation of $2mm$ is charged by connecting it to a $300V$ supply. The energy density is:

• A. $0.01J/m^3$
• B. $0.1J/m^3$
• C. $1.0J/m^3$
• D. $10J/m^3$

Answer 1

The correct option is B $0.1J/m^3$

The energy density of parallel plate capacitor is given by

$U=\frac{1}{2}\epsilon E^2=\frac{1}{2}\epsilon {\left(\frac{V}{d}\right)}^2$

$U=\frac{1}{2}\times 8.85\times {10}^{-12}\frac{C^2}{N{m}^2}\times {\left(\frac{300volts}{2\times {10}^{-3}}\right)}^2$

$U=0.1J/m^2$