Answer:
U/U₀ = 1/2
Explanation:
The energy stored in the capacitor initially is U₀ = 1/2C₀V². When the separation distance doubles, the new energy stored is U = 1/2CV².
Since the capacitance of a parallel plate capacitor is C = εA/d. So, C ∝ 1/d
So, C/C₀ = d₀/d = 1/2. Since d = 2d₀ that is, the separation distance doubles
U/U₀ = 1/2CV²/1/2C₀V² = C/C₀ = d₀/d = 1/2
So, U/U₀ = 1/2