$A$ hollow metallic sphere of radius $10 \; cm$ is charged such that the potential at its surface is $80 \; V$. The potential at the centre of the sphere would be (in $; V$)

There are four concentric shells $A, B, C$ and $D$ of radii $a, 2a, 3a$ and $4a$ respectively. Shells $B$ and $D$ are given charges $+q$ and $-q$ respectively. Shell $C$ is now earthed. The potential difference $V_A - V_C$ is:

$A$ charge of $10^{-3} \ \mu C$ is placed at the origin $(0, 0)$ of an $X-Y$ coordinate system. Two points $A$ and $B$ are located at $(\sqrt{2}, \sqrt{2})$ and $(2, 0)$ respectively. The potential difference between points $A$ and $B$ is ....... $V$.

If a charge is shifted from a low potential region to a high potential region,the electric potential energy

Two charged spheres of radii $R_1$ and $R_2$ have equal surface charge density. The ratio of their potential is

Two conducting spheres of radii $r_1$ and $r_2$ have the same electric field intensity near their surfaces. The ratio of their electric potentials is