The electric potential at the surface of an atomic nucleus $(Z=50)$ of radius $9 \times 10^{-15} \ m$ is . . . . . . .

Four equal charges $Q$ are placed at the four corners of a square of side $a$. The work done in moving a charge $-Q$ from its centre to infinity is

Is electrostatic potential a vector or a scalar quantity?

$64$ drops of mercury,each charged to a potential of $10\,V$,are combined to form one bigger drop. The potential of this bigger drop will be.......$V$ (Assume all the drops to be spherical).

Two identical thin rings each of radius $R$ meters are coaxially placed at a distance $R$ meters apart. If $Q_1$ coulomb and $Q_2$ coulomb are respectively the charges uniformly spread on the two rings,the work done in moving a charge $q$ from the centre of one ring to that of other is

Along the $X$-axis,three charges $\frac{q}{2}, -q$ and $\frac{q}{2}$ are placed at $x=0, x=a$ and $x=2a$ respectively. The resultant electric potential at $x=a+r$ (if $a << r$) is: ($\varepsilon_0$ is the permittivity of free space)