Two spherical conductors $A$ and $B$ of radius $a$ and $b (b > a)$ are placed in air concentrically $B$ is given charge $+ Q$ coulomb and $A$ is grounded. The equivalent capacitance of these is

Eight drops of mercury of equal radii possessing equal charges combine to form a big drop. Then the capacitance of bigger drop compared to each individual small drop is……..$times$

The capacitance $(C)$ for an isolated conducting sphere of radius $(a)$ is given by $4\pi \varepsilon_0a$. If the sphere is enclosed with an earthed concentric sphere. The ratio of the radii of the spheres $\frac{n}{{(n – 1)}}$  being then the  capacitance of such a sphere will be increased by a factor

Two metal spheres of capacitance ${C_1}$ and ${C_2}$ carry some charges. They are put in contact and then separated. The final charges ${Q_1}$ and ${Q_2}$ on them will satisfy

Consider the situation shown in the figure. The capacitor $A$ has a charge $q$ on it whereas $B$ is uncharged. The charge appearing on the capacitor $B$ a long time after the switch is closed is