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 $\,F$)

$A$ capacitor is formed by two concentric spherical shells. The potential of the shell with radius $R_1$ is $V_1$ and the potential of the shell with radius $R_2$ is $V_2$. What is the potential at a point at a distance $x$ from the center? $(R_2 > x > R_1)$

Consider a charged cylindrical capacitor. The magnitude of the electric field $\vec{E}$ in its annular region:

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

The radii of the inner and outer spheres of a spherical capacitor are $8 \ cm$ and $9 \ cm$ respectively. The outer sphere is earthed and the inner sphere is charged. If the space between the concentric spheres is filled with a liquid of dielectric constant $5$,the capacitance of the capacitor is:

$A$ drop of capacitance $1 \ \mu F$ is divided into $8$ identical drops. The capacitance of each small drop is .... $\mu F$.