A capacitor of capacitance C =900 pF is charged fully by 100 V battery B as shown in figure (a). Then it is disconnected from the battery and connected to another uncharged capacitor of capacitance C =900 pF as shown in figure (b). The electrostatic energy stored by the system (b) is :

Question

A capacitor of capacitance C =900 pF is charged fully by 100 V battery B as shown in figure (a). Then it is disconnected from the battery and connected to another uncharged capacitor of capacitance C =900 pF as shown in figure (b). The electrostatic energy stored by the system (b) is : (A) 1.5 × 10-6 J (B) 4.5 × 10-6 J (C) 3.25 × 10-6 J (D) 2.25 × 10-6 J

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<img class="img-fluid question-image" alt="image" src="https://cdn.tardigrade.in/img/question/physics/cd93425ba6273d699dcd28d903e01fdb-.png" /> We have the initial energy as (1/2) CV 2=(1/2) × 9 × 10-10 × 1002=4.5 × 10-6 J Now the capacitor is disconnected and is connected to another 900 pF capacitor. In the steady situation, the two capacitors have their positive plates at the same potential. Let the common potential difference be V '. The charge on each capacitor is Q prime= CV '. By charge conservation, Q prime=Q / 2. This implies V prime=V / 2. The total energy of the system is =2 ×(1 / 2) Q prime V '=(1 / 4) QV =2.25 × 10-6 J Thus we get the electrostatic energy stored by the system as (1/2)(C1+C2) V2= (1/2)(2 × 9 × 10-10) × 502=2.25 × 10-6

Q. A capacitor of capacitance $C = 900 pF$ is charged fully by $100 V$ battery $B$ as shown in figure (a). Then it is disconnected from the battery and connected to another uncharged capacitor of capacitance $C = 900 pF$ as shown in figure (b). The electrostatic energy stored by the system (b) is :

$1.5 \times 1 0^{- 6} J$

$4.5 \times 1 0^{- 6} J$

$3.25 \times 1 0^{- 6} J$

$2.25 \times 1 0^{- 6} J$

Q. A capacitor of capacitance C=900pF is charged fully by 100V battery B as shown in figure (a). Then it is disconnected from the battery and connected to another uncharged capacitor of capacitance C=900pF as shown in figure (b). The electrostatic energy stored by the system (b) is :

1.5×10−6J

4.5×10−6J

3.25×10−6J

2.25×10−6J

Q. A capacitor of capacitance $C = 900 pF$ is charged fully by $100 V$ battery $B$ as shown in figure (a). Then it is disconnected from the battery and connected to another uncharged capacitor of capacitance $C = 900 pF$ as shown in figure (b). The electrostatic energy stored by the system (b) is :

$1.5 \times 1 0^{- 6} J$

$4.5 \times 1 0^{- 6} J$

$3.25 \times 1 0^{- 6} J$

$2.25 \times 1 0^{- 6} J$