$A$ uniform electric field of magnitude $100 \ V/m$ in space is directed along the line $y = 3 + x$. Find the potential difference between point $A(3, 1)$ and $B(1, 3)$ in Volts.

What is an equipotential surface? Draw equipotential surfaces for:
$(1)$ $A$ single point charge
$(2)$ $A$ dipole (charges $+q$ and $-q$ at a small distance)
$(3)$ Two $+q$ charges at a small distance
$(4)$ $A$ uniform electric field.

The figure shows equipotential surfaces concentric at $O$. The magnitude of the electric field at a distance $r$ metres from $O$ is

Equipotential surfaces at a very large distance from a collection of charges whose total sum is not zero are approximately . . . . . . .

In moving from $A$ to $B$ along an electric field line,the electric field does $6.4 \times 10^{-19} \, J$ of work on an electron. If $\phi_1$ and $\phi_2$ are equipotential surfaces,then the potential difference $(V_C - V_A)$ is.....$V$.

Assertion $(A)$: In a region of constant potential,the electric field is zero and there can be no charge inside the region.
Reason $(R)$: According to Gauss's law,the charge inside the region should be zero if the electric field is zero.