The points having equal potentials are:

Equipotential surfaces are shown in the figure. Then the electric field strength will be

$A$ charge is moved from point $A$ to points $B, C, D,$ and $E$ in the electric field of a charge $Q$ placed at the center of a circle. The work done will be:

$A$ 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 .......

This question has Statement-$1$ and Statement-$2$. Of the four choices given after the Statements,choose the one that best describes the two Statements.
Statement-$1$: No work is required to be done to move a test charge between any two points on an equipotential surface.
Statement-$2$: Electric lines of force at the equipotential surfaces are mutually perpendicular to each other.

Describe schematically the equipotential surfaces corresponding to
$(a)$ a constant electric field in the $z$-direction,
$(b)$ a field that uniformly increases in magnitude but remains in a constant (say,$z$) direction,
$(c)$ a single positive charge at the origin,and
$(d)$ a uniform grid consisting of long equally spaced parallel charged wires in a plane.