A capacitor C₁ with capacitance 24 μF is initially charged by connecting it to a source of potential

Question

A capacitor C₁ with capacitance 24 μF is initially charged by connecting it to a source of potential difference Vₒ = 120 V. The source of potential difference is then disconnected. When capacitor C₁ is connected in parallel with another capacitor C₂ with capacitance 12 μF, what is the final energy of the system?

Answer 1

A capacitor C₁ with capacitance 24 μF is initially charged by connecting it to a source of potential difference Vₒ = 120 V. The source of potential difference is then disconnected. When capacitor C₁ is connected in parallel with another capacitor C₂ with capacitance 12 μF, what is the final energy of the system?

0.1183 J
0.1525 J
0.1152 J ✓
0.1225 J

Explanation

Initial charge: Q = CV = 24 × 10⁻⁶ × 120 = 2.88 × 10⁻³ C. Charge is conserved after the source is removed.

Total capacitance in parallel = 24 + 12 = 36 μF, so V = Q ÷ C = 80 V.

Energy = ½CV² = ½ × 36 × 10⁻⁶ × 80² = 0.1152 J.

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