Two infinite, parallel, non-conducting sheets carry equal positive charge density $\sigma$. One is placed in the $yz$ plane and the other at distance $x=a$. Take potential $V=0$ at $x=0$.

Figure shows some equipotential lines distributed in space. A charged object is moved from point $A$ to point $B$

In the electric field of a point charge $q$ which is located at center of sphere as shown, a certain charge is carried from point $A$ to $B, C, D$ and $E$. Then work done by external agent

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

In moving from $A$ to $B$ along an electric field line, the electric field does $6.4\times {10}^{-19} \mathrm{J}$ of work on an electron. If ${\varphi }_1$ and ${\varphi }_2$ are equipotential surfaces, then the potential difference $\left(V_C-V_A\right)$ is