Question

The switches in figure (a) and (b) are closed at $t=0$ and reopened after a long time at $t=t_0$.

• A. The charge on C just after $t=0$ is $\epsilon$ C.
• B. The charge on C just long $t=0$ is $\epsilon$ C.
• C. The current in L just before $t=t_0$ is $\frac{\epsilon }{R}$.
• D. The current in L long after $t=t_0$ is $\frac{\epsilon }{R}$.

Answer 1

Answer: (B), (C)

The correct options are
B The charge on C just long $t=0$ is $\epsilon$ C.
C The current in L just before $t=t_0$ is $\frac{\epsilon }{R}$.

When a capacitor is connected to a battery for a long time, it behaves as a open circuit.

Hence, from Kirchoff's Voltage law:

$E-\frac{q}{C}=0$

$⟹q=EC$

When an inductor is connected to a battery for a long time, it behaves as a short circuit.

Hence, from the Kirchoff's Voltage law:

$E-IR=0$

$⟹I=\frac{E}{R}$