Question

The magnetic potential energy stored in certain inductor is equal to energy stored in capacitor. If charge on capacitor is $20\mu C$, capacitance is $10\mu F$ and inductance is 40 $H$, find current $i$ in inductor.

• A. 2 $mA$
• B. 3 $mA$
• C. 5 $mA$
• D. 1 $mA$

Answer 1

The correct option is D 1 $mA$

$\frac{Q^2}{2C}=\frac{1}{2}L{i}^2$
$i=\sqrt{\frac{Q^2}{LC}}$
$=\frac{Q}{\sqrt{LC}}=\frac{20\times {10}^{-6}}{\sqrt{40\times 10\times {10}^{-6}}}=\frac{20\times {10}^{-6}}{20\times {10}^{-3}}={10}^{-3}=1mA$