Energy Stored & Force between Plates question from NEET 2001 (AIPMT)

Answer: (a)

1. Energy density $u = \frac{1}{2}\varepsilon_0 E^2$.
2. Uniform field $E = \frac{V}{d}$, so $u = \frac{1}{2}\varepsilon_0 \frac{V^2}{d^2}$.
3. Options (c) and (d) are total energy, not energy per unit volume.
4. So the answer is (a) $\frac{1}{2}\varepsilon_0\frac{V^2}{d^2}$.