$A$ spherical capacitor consists of two concentric spherical conductors. Find the capacitance of the spherical capacitor if the outer radius is $2 R$ and the inner radius is $R$.

Assume each oil drop has a capacitance of $C$. If $n$ drops are combined to form a bigger drop,then the capacitance of the bigger drop $C^{\prime}$ would be

The graph shows the variation of voltage $V$ across the plates of two capacitors $A$ and $B$ versus the charge $Q$ stored in them. Then:

The potentials on the plates of a capacitor are $+20 \,V$ and $-20 \,V$. The charge on the plate is $40 \,C$. The capacitance of the capacitor is (in $\,F$)

The Earth is assumed to be a charged conducting sphere having volume $V$ and surface area $A$. The capacitance of the Earth in free space is $(\epsilon_0 = \text{permittivity of free space})$

$A$ cylindrical capacitor has inner and outer conductors whose radii are in the ratio $10:1$. The inner conductor is replaced by a wire whose radius is half of the original inner conductor. To obtain the same capacitance as the original capacitor,by what ratio should the length of the wire be increased?