Question

For the arrangement shown in the figure, the switch is closed at $t=0.C_2$ is initially uncharged while $C_1$ has a charge of $2\mu C$. Find the current coming out of the battery just after the switch is closed.

Answer 1

At $t=0$ equivalent resistance of an uncharged capacitor is zero and a charged capacitor is like a battery of $emf=$ potential difference across the capacitor.

$V_{C_1}=q_1/C_1=2V$

$\therefore$ Net emf of the circuit $=9-2=7V$

or $9+2=11V$

Net resistance $=30+\frac{30\times 60}{30+60}=50\Omega$

$\therefore$ Current at $t=0$ would be $i_o=\frac{7}{50}A$ or $\frac{11}{50}A$