In the given figure,initially the capacitor is uncharged. The ratio of current at $t = 0$ and $t = \infty$ will be:

Find the time constant for the given circuit.

$A$ parallel plate capacitor is charged to a potential difference of $50 \, V$. It is discharged through a resistance. After $1 \, s$,the potential difference between the plates becomes $40 \, V$. Then:

In an $RC$ circuit as shown below,both switches are open initially. Now switch $S_1$ is closed and $S_2$ is kept open. ($q$ is the charge on the capacitor and $\tau = RC$ is the capacitive time constant). Which of the following statements is correct?

Given,
${R_1} = 1\,\Omega, R_2 = 2\,\Omega$
${C_1} = 2\,\mu F, C_2 = 4\,\mu F$
The time constants (in $\mu s$) for the circuits $I, II, III$ are respectively:

$A$ $1 \mu F$ capacitor $C$ is connected to a battery of $10 V$ through a resistance of $1 \text{ M}\Omega$. The voltage across $C$ after $1 \text{ s}$ is approximately: (in $V$)