Question

Change in enegry of the capacitor is :

• A. $6\times {10}^{-8}J$
• B. $-1215\times {10}^{-10}J$
• C. $1215\times {10}^{-10}J$
• D. $4.05\times {10}^{-11}J$

Answer 1

Answer: (D)

The correct option is D $4.05\times {10}^{-11}J$

Change in energy of the capacitor will be the difference between initial and final energy.

$E_{diff}=E_{initial}-E_{final}$

$=\frac{1}{2}{C}_i{V}^2-\frac{1}{2}{C}_f{V}^2$

$=\frac{V^2}{2}\left(A{\epsilon }_0\right)\left(\frac{1}{d}-\frac{1}{d^{\prime }}\right)$

$=\frac{9\times {10}^4}{2}\left(10\times {10}^{-4}\times 9\times {10}^{-12}\right)\left(\frac{1}{2\times {10}^{-2}}-\frac{1}{2.5\times {10}^{-2}}\right)$

$=4.05\times {10}^{-11}J$