The distance between the plates of a charged parallel plate capacitor is $5\  cm$ and electric field inside the plates is $200\  Vcm^{-1}$. An uncharged metal bar of width $2\  cm$ is fully immersed into the capacitor. The length of the metal bar is same as that of plate of capacitor. The voltage across capacitor after the immersion of the bar is......$V$

Consider the situation shown in the figure. The capacitor $A$ has a charge $q$ on it whereas $B$ is uncharged. The charge appearing on the capacitor $B$ a long time after the switch is closed is

The capacitance of a parallel plate capacitor is $12\,\mu \,F$. If the distance between the plates is doubled and area is halved, then new capacitance will be.........$\mu \,F$

Two conducting shells of radius $a$ and $b$ are connected by conducting wire as shown in figure. The capacity of system is :

A cylindrical capacitor has two co-axial cylinders of length $20 \,cm$ and radii $2 r$ and $r$. Inner cylinder is given a charge $10 \,\mu C$ and outer cylinder a charge of $-10 \,\mu C$. The potential difference between the two cylinders will be

What is capacitor ? And explain capacitance. Give its $\mathrm{SI}$ unit.