If the circumference of a sphere is $2 \ m$,find the capacitance of the sphere in water in $pF$. (Take dielectric constant of water $K = 80$)

Taking the Earth to be a metallic sphere,its capacity will approximately be

When a $0.75 \mu F$ capacitor is charged to a voltage of $20 \ V$,then the magnitude of charge on each plate is (in $\mu C$)

$A$ capacitor of unknown capacitance $C$ is connected across a battery of $V$ volt. The charge stored in it becomes $Q$ coulomb. When the potential across the capacitor is reduced by $V^{\prime}$ volt,the charge stored in it becomes $Q^{\prime}$ coulomb. The capacitance $C$ is:

The ratio of charge to potential of a body is known as

Two spherical conductors $A$ and $B$ of radii $a$ and $b$ $(b > a)$ are placed concentrically in air. The two are connected by a copper wire as shown in the figure. Then the equivalent capacitance of the system is