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

Show that the direction of electric field at a given is normal to the equipotential surface passing through that point.

Which of the following figure shows the correct equipotential surfaces of a system of two positive charges?

A point charge $+Q$ is placed just outside an imaginary hemispherical surface of radius $R$ as shown in the figure. Which of the following statements is/are correct?

(IMAGE)

$[A]$ The electric flux passing through the curved surface of the hemisphere is $-\frac{\mathrm{Q}}{2 \varepsilon_0}\left(1-\frac{1}{\sqrt{2}}\right)$

$[B]$ Total flux through the curved and the flat surfaces is $\frac{Q}{\varepsilon_0}$

$[C]$ The component of the electric field normal to the flat surface is constant over the surface

$[D]$ The circumference of the flat surface is an equipotential

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

Equipotential surfaces associated with an electric field which is increasing in magnitude along the $x$-direction are