The correct option (A) 0.1224μJ
Explanation:
capacitance of capacitor AB, C1 = (A∈0/d1)
capacitance of capacitor CD, C2 = [(A2∈0)/d2]
combined capacitance : C = [(C1C2)/(C1 + C2)] = [(A1A2∈0) / (A1d1 + A2d1)]
∴ C = [(π∈0r12r22)/(r12d2 + r22d1)]
= π∈0[{(5 × 10–2)2 (6 × 10–2)2}/{(5 × 10–2)2 × 3 × 10–3 + (6 × 10–2)2 × 2 × 10–3}]
= (30/49)π∈0
Energy stored = U = (1/2)CV2
= (1/2) [(30/49)π∈0] (120)2
= 0.1224 × 10–6
= 0.12μJ