Capacitance of an isolated conducting sphere of radius $R_{1}$ becomes $n$ times when it is enclosed by a concentric conducting sphere of radius $R_{2}$ connected to earth. The ratio of their radii $\left(\frac{ R _{2}}{ R _{1}}\right)$ is:

Sixty-four drops are jointed together to form a bigger drop. If each small drop has a capacitance $C$, a potential $V$, and a charge $q$, then the capacitance of the bigger drop will be

Capacitance (in $F$) of a spherical conductor with radius $1\, m$ is

Two metallic charged spheres whose radii are $20\,cm$ and $10\,cm$ respectively, have each $150\,micro - coulomb$ positive charge. The common potential after they are connected by a conducting wire is

In an isolated parallel plate capacitor of capacitance $C$, the four surface have charges ${Q_1}$, ${Q_2}$, ${Q_3}$ and ${Q_4}$ as shown. The potential difference between the plates is

A capacitor is made of two square plates each of side $a$ making a very small angle $\alpha$ between them, as shown in figure. The capacitance will be close to