Question

If the potential of a capacitor having capacity of $6\mu F$ is increased from 10 V to 20 V, then increase in its energy will be :

• A. $4\times {10}^{-4}J$
• B. $5\times {10}^{-4}J$
• C. $9\times {10}^{-4}J$
• D. $12\times {10}^{-6}J$

Answer 1

The correct option is C $9\times {10}^{-4}J$

Initial energy $U_i=\frac{1}{2}C{V}_i^2$ and final energy $U_f=\frac{1}{2}C{V}_f^2$
Increase in energy $=\Delta U=U_f-U_i=\frac{1}{2}C(V_f^2-V_i^2)$

$=\frac{1}{2}\times (6\times {10}^{-6})\times [{20}^2-{10}^2]$

$=9\times {10}^{-4}J$