JAMB Physics 2011 Paper

Concept:Electric potential at a point is the work done in bringing a unit positive charge from infinity to that point against the electric field.Explanation:For a point charge $q$, the electric field at distance $r$ is given by $E = \frac{q}{4\pi\varepsilon_0 r^2}$.The potential $V$ is obtained by integrating the field from infinity to $r$.$$V = \int_{\infty}^{r} -E \, dr = \frac{q}{4\pi\varepsilon_0 r}$$Therefore, the correct expression only depends on $q$ and $r$, not on $r^2$.Answer:$$V = \frac{q}{4\pi\varepsilon_0 r}$$So the correct option is D.