
Net capacity $ =\frac{\mathrm{C} \times 2 \mathrm{C}}{\mathrm{C}+2 \mathrm{C}}=\frac{2 \mathrm{C}}{3}$
$=\frac{2}{3} \times 6=4\, \mu \mathrm{F}$
Potential difference $=10 \mathrm{\,V}$
$q=\mathrm{CV}=4 \times 10^{-6} \times 10=40\, \mu \mathrm{C}$
Reason : In a parallel plate capacitor both plates always carry equal and opposite charge.

${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
