$\mathrm{V}=\mathrm{V}_{1}+\mathrm{V}_{2}$
$\mathrm{V}=\frac{\mathrm{kQ}_{1}}{\mathrm{r}}+\frac{\mathrm{kQ}_{2}}{\mathrm{R}_{2}}=\mathrm{k}\left(\frac{\mathrm{Q}_{1}}{\mathrm{r}}+\frac{\mathrm{Q}_{2}}{\mathrm{R}_{2}}\right)$
${R_1} = 1\,\Omega $ $C_1 \,= 2\,\mu F$
${R_2} = 2\,\Omega $ $C_2 \,= 4\,\mu F$
The time constants ( in $\mu\, s$) for the circuits $I, II, III$ are respectively





