Question

The mean electric energy density between the plates of a charged capacitor is (here Q = Charge on the capacitor and A = Area of the capacitor plate)

• A. $\frac{Q^{2}}{2\varepsilon_{0}A^{2}}$
• B. $\frac{Q}{2\varepsilon_{0}A^{2}}$
• C. $\frac{Q^{2}}{2\varepsilon_{0}A}$
• D. None

Answer 1

Answer: (A)

$\frac{Q^{2}}{2\varepsilon_{0}A^{2}}$

Answer 2

Energy density $= \frac{1}{2}\varepsilon_{0}E^{2} = \frac{1}{2}\varepsilon_{0}\left( \frac{Q}{A\varepsilon_{0}} \right)^{2} = \frac{Q^{2}}{2\varepsilon_{0}A^{2}}$.