Work done in moving a positive charge on an equipotential surface is

$A$ charge of $20 \, \mu C$ is placed at the origin. What is the potential difference between the points $(5a, 0)$ and $(-3a, 4a)$?

Positive and negative point charges of equal magnitude are kept at $(0, 0, a/2)$ and $(0, 0, -a/2)$,respectively. The work done by the electric field when another positive point charge is moved from $(-a, 0, 0)$ to $(0, a, 0)$ is

Draw an equipotential surface of two identical positive charges for small distance.

$A$ uniform electric field of magnitude $100 \ V/m$ in space is directed along the line $y = 3 + x$. Find the potential difference between point $A(3, 1)$ and $B(1, 3)$ in Volts.

Define an equipotential surface.