Question

In an oscillating LC circuit, $L =3.00\, mH$ and $C =2.70 \,\mu F .$ At $t =0$ the charge on the capacitor is zero and the current is $2.00\, A$. The maximum charge that will appear on the capacitor will be

• A. $1.8 \times 10^{-5} C$
• B. $18 \times 10^{-5} C$
• C. $9 \times 10^{-5} C$
• D. $90 \times 10^{-5} C$

Answer 1

Answer: (B)

$\frac{ Q ^{2}}{2 C }=\frac{ LI ^{2}}{2}$
$\frac{ Q ^{2}}{2 \times 2.7 \times 10^{-6}} =\frac{3 \times 10^{-3} \times 4^{2}}{2}$
$Q ^{2}=12 \times 10^{-3} \times 2.7 \times 10^{-6}$
$=32.4 \times 10^{-9}$
$Q =18 \times 10^{-5} C$