Question

An insulating solid sphere of radius $R$ has a uniform volume charge density and total charge $Q$. Find the electric field at a point outside the sphere at a distance of $r$ from its centre.

• A. $\frac{Q}{8\pi {ϵ}_0{r}^2}$
• B. $\frac{Q}{4\pi {ϵ}_0{R}^2}$
• C. $\frac{Q}{2\pi {ϵ}_0{r}^2}$
• D. $\frac{Q}{4\pi {ϵ}_0{r}^2}$

Answer 1

The correct option is D $\frac{Q}{4\pi {ϵ}_0{r}^2}$

For an outside point, sphere will act as a point charge, hence electric field will be given by

$E_{outside}=\frac{kQ}{r^2}$