A) \[4.5\times {{10}^{-6}}J\]
B) \[2.25 \times 1{{0}^{-6}}\,J\]
C) Zero
D) \[9\times 1{{0}^{-}}^{6}\,J\]
Correct Answer: B
Solution :
\[\operatorname{Energy} stored in the capacitor =\frac{1}{2}\frac{{{Q}^{2}}}{C}\] \[\operatorname{Q}=\,\,CV=900\times {{10}^{-12}}F\times 100\,V\] \[\therefore \,\, Q=\,\,9\times {{10}^{-8}}\,C\] Energy of the capacitor when fully charged \[=\,\,\frac{1}{2}\frac{{{Q}^{2}}}{C}=4.5\times {{10}^{-\,6}}J\] The total charge is conserved. In figure (b), total capacitance \[= C = 2 \times C = 2 \times 900 pF\] \[\therefore \,\,\,\,Final\,\,Energy=\,\,\frac{1}{2}\frac{{{Q}^{2}}}{C}=\frac{1}{2}.\frac{{{Q}^{2}}}{2C}\] \[\therefore \,\,\, Final Energy =\,\,\frac{4.5\times {{10}^{-\,6}}J}{2}= 2.25 \times 1{{0}^{-}}^{6}J\]You need to login to perform this action.
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