The capacitance of a capacitor depends on:

Four capacitors,each of $25\,\mu F$,are connected as shown in the figure. The $dc$ voltmeter reads $200\,V$. The charge on each plate of the capacitor is

Between a solid sphere and a hollow sphere of the same radius, which has a greater capacity to hold electric charge?

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A:$ Two metallic spheres are charged to the same potential. One of them is hollow and another is solid,and both have the same radii. The solid sphere will have a lower charge than the hollow one.
Reason $R:$ Capacitance of metallic spheres depends on the radii of the spheres.
In the light of the above statements,choose the correct answer from the options given below.

$A$ 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 capacitance of a spherical capacitor is $100 \ pF$. If the spacing between the two spheres is $1 \ cm$,then the radius of the inner sphere of the capacitor is: (in $cm$)