Practice question

**Work done charging capacitor** is integral ∫ V dQ = ∫ Q/C dQ = Q²/2C, stored as electrostatic energy. When capacitor discharges, energy released as heat or work, explaining spark when shorted, energy proportional to V². The energy density in an electric field is given by u = (1/2) ε₀ E² . This arises from the energy stored in a capacitor ( U = (1/2) C V² ), scaled over the volume. For a parallel plate capacitor, E = (V/d) , C = (ε₀ A/d) , so U = (1/2) (ε₀ A/d) (E d)² = (1/2) ε₀ E² (A d) , where A d is