A point charge $q$ is placed near a hemispherical surface without base, cylindrical surface with one end open, spherical surface, and hemispherical surface with the base as shown in the figures in $a,b,c$and $d$respectively. In which of the following cases, the flux crossing through the surface is zero?

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

An electric field is given by $E_{\mathrm{x}}=-\left(2x^3\right)\hat{\mathrm{i}} \mathrm{N} {\mathrm{C}}^{-1}$. What is the potential at the point $(1, -2)$ if the potential at a point $(2, 4)$ is taken to be zero?

Three identical small dipoles are arranged as shown in the figure. What will be the net electric field at $P$? ($k=\frac{1}{4\pi {\epsilon }_0}$)