Shows that how the electrostatic potential varies with $\mathrm{r}$ for a point charge.

A table tennis ball which has been covered with conducting paint is suspended by a silk thread so that it hang between two plates, out of which one is earthed and other is connected to a high voltage generator. This ball

A spherical drop of mercury having a potential of $2.5\, V$ is obtained as a result of merging $125$ droplets. The potential of constituent droplets would be........$V$

Two concentric hollow metallic spheres of radii $r_1$ and $r_2 (r_1 > r_2)$ contain charges $q_1$ and $q_2$ respectively. The potential at a distance $x$ between $r_1$ and $r_2$ will be

An infinitely long thin wire, having a uniform charge density per unit length of $5 nC / m$, is passing through a spherical shell of radius $1 m$, as shown in the figure. A $10 nC$ charge is distributed uniformly over the spherical shell. If the configuration of the charges remains static, the magnitude of the potential difference between points $P$ and $R$, in Volt, is. . . .

[Given: In SI units $\frac{1}{4 \pi \epsilon_0}=9 \times 10^9, \ln 2=0.7$. Ignore the area pierced by the wire.]

Three concentric metal shells $A, B$ and $C$ of respective radii $a, b$ and $c (a < b < c)$ have surface charge densities $+\sigma,-\sigma$ and $+\sigma$ respectively. The potential of shell $B$ is