If a unit positive charge is taken from one point to another over an equipotential surface,then

$A$ point charge $+q$ is placed at the origin. The work done in moving another point charge $-Q$ along the straight line path $AB$ from point $A$ with coordinates $(0, a)$ to point $B$ with coordinates $(a, 0)$ is .......

$S_1$ and $S_2$ are two equipotential surfaces on which the potentials are not equal. Which of the following statements is incorrect?

The nature of the equipotential surface for a point charge is:

$A$ uniform electric field is prevailing in the $X$-direction in a certain region. The coordinates of points $P$,$Q$,and $R$ are $(0,0)$,$(2,0)$,and $(0,2)$ respectively. Which of the following alternatives is true for the potentials at these points?

The figure shows two parallel equipotential surfaces $A$ and $B$ kept a small distance $r$ apart from each other. $A$ point charge of $q$ coulomb is taken from the surface $A$ to $B$. The amount of net work done will be