The unit of permittivity of free space is

$A$ spherical condenser has inner and outer spheres of radii $a$ and $b$ respectively. The space between the two is filled with air. The difference between the capacities of two condensers formed when the outer sphere is earthed and when the inner sphere is earthed will be:

If the capacity of a spherical conductor is $1 \text{ picofarad}$,then its diameter would be

The capacity of a spherical conductor in the $MKS$ system is:

The capacitance of a capacitor depends on:

$1000$ small water drops,each of capacitance $C$,join together to form one large spherical drop. The capacitance of the bigger sphere is ......... $C$.