Question

A positive charge '$Q$' is placed on a conducting spherical shell with inner radius $R_1$ and outer radius $R_2$. A particle with charge $q$ is placed at the centre of the spherical cavity. The magnitude of the electric field at a point in the cavity, a distance $r$ from center is

• A. Zero
• B. $\frac{Q}{4\pi {\epsilon }_0{r}^2}$
• C. $\frac{q}{4\pi {\epsilon }_0{r}^2}$
• D. $\frac{(q+Q)}{4\pi {\epsilon }_0{r}^2}$

Answer 1

Answer: (C)

$\frac{q}{4\pi {\epsilon }_0{r}^2}$

$\int Eds=\frac{q_{in}}{{\epsilon }_0}$
$=\frac{1}{4\pi {\epsilon }_0}\frac{q}{r^2}$