$A$ parallel plate capacitor is charged. Then the battery is removed. Now,if the plates are pulled apart,

Two circular plates each of radius 'r' are kept parallel to each other distance 'd' apart. The capacitance of the capacitor formed is '$C_1$'. If the radius of each of the plates is increased to $\sqrt{3}$ times the earlier radius and their distance of separation decreased to half the initial value, the capacitance now becomes '$C_2$'. The ratio $C_1 : C_2$ is

In a parallel plate capacitor,if $10^{12}$ electrons pass from one plate to another,a potential difference of $10 \,V$ is developed across the plates. The capacitance of the capacitor is

$A$ parallel plate capacitor has rectangular plates of area $400 \, cm^2$ separated by a distance of $2 \, mm$ with air as the medium. If a potential difference of $200 \, V$ is applied across the capacitor,what is the charge on the plates?

The unit of absolute permittivity is

Five identical capacitor plates,each of area $A$,are arranged such that adjacent plates are at a distance $d$ apart. The plates are connected to a source of $emf$ $V$ as shown in the figure. Then the charges on plates $1$ and $4$ are,respectively: