There are two equipotential surfaces as shown in the figure. The distance between them is $r$. If a charge of $-q \text{ C}$ is moved from surface $A$ to surface $B$,the resultant work done will be:

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

Draw an equipotential surface for an electric dipole.

Two point charges $-Q$ and $+Q / \sqrt{3}$ are placed in the $xy$-plane at the origin $(0,0)$ and a point $(2,0)$,respectively,as shown in the figure. This results in an equipotential circle of radius $R$ and potential $V = 0$ in the $xy$-plane with its center at $(b, 0)$. All lengths are measured in meters.
$(1)$ The value of $R$ is. . . . meter.
$(2)$ The value of $b$ is. . . . . .meter.

How much work is required to move a charge $(-q)$ from point $A$ to point $C$ in the presence of a charge $+Q$ at point $B$ as shown in the figure?

The angle between the electric lines of force and the equipotential surface is (in $^{\circ}$)