The diagrams below show regions of equipotentials. $A$ positive charge $q$ is moved from $A$ to $B$ in each diagram.

$A$ metallic sphere has a charge of $10\,\mu C$. $A$ unit negative charge is brought from $A$ to $B$,both $100\,cm$ away from the sphere,with $A$ being east of it and $B$ being west of it. The net work done is........$joule$.

$A$ charge $+Q$ is placed at the centre of a circular path of radius $r$. The work done to bring a charge $+q$ from one end of the diameter to the other end of the circular path in the electric field produced by charge $+Q$ is $.......$

$A$ 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:

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.

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