Question

In a charged capacitor the energy is stored in:

• A. both in positive and negative charges
• B. positive charges
• C. the edges of the capacitor plates
• D. the electric field between the plates

Answer 1

Answer: (D)

the electric field between the plates

We know energy per unit volume stored in electric field $=\frac{1}{2}{\epsilon }_0{E}^2$
in parallel plate capacitor $E=\frac{6}{{\epsilon }_0}$
Energy density $=\frac{1}{2}{\epsilon }_0\frac{6^2}{{\epsilon }_o^2}$
$Energy=\frac{1}{2}{\epsilon }_0\frac{1}{{\epsilon }_0}(\frac{Q}{A}{)}^2\cdot (A\cdot d)\to volume$
$E=\frac{1}{2}\frac{1}{{\epsilon }_0}\frac{Q^{2}d}{A}$
We know $C=\frac{{\epsilon }_{0}A}{d}$
$E=\frac{1}{2}\frac{Q^2}{C}(Q=CV)$
$E=\frac{1}{2}C{V}^2$