Question

A charge q is placed at O in the cavity in a spherical uncharged conductor, Point S is outside the conductor. If q is displaced from O towards S (stilI remaining within the cavity)

• A. electric field at S will increase
• B. electric field at S will decrease
• C. electric field at S will first increase and then decrease
• D. electric field at S will not change

Answer 1

The correct option is D electric field at S will not change

By Gauss's law , the electric field at S is $E.4\pi r^2=\frac{q_{en}}{{ϵ}_0}\Rightarrow E=\frac{q_{en}}{4\pi {ϵ}_0{r}^2}$ where $r=$ distance from center to S.

When we move charge q towards S within cavity, the enclosed charge $q_{en}$ will remain same i.e, $q_{eq}=q$.

Thus, the field at S will not change.