Question

The capacity of a condenser is 20$\mu F$ and the potential is 20 V. The energy released an discharging it fully will be

• A. $2\times {10}^{-3}J$
• B. $4\times {10}^{-3}J$
• C. $8\times {10}^{-3}J$
• D. $10\times {10}^{-3}J$

Answer 1

The correct option is B $4\times {10}^{-3}J$

The energy released on discharging will be
$U=\frac{1}{2}C{V}^2$
$=\frac{1}{2}\times 20\times {10}^{-6}\times 20\times 20=4\times {10}^{-3}J$