Question

The force between two point charges placed in a material medium of dielectric constant ${\epsilon }_r$ is $F$. If the material is removed, then the force between them becomes:

• A. ${\epsilon }_{r}F$
• B. $\epsilon F$
• C. $\frac{F}{{\epsilon }_r}$
• D. $\frac{\epsilon }{F}$
• E. ${\epsilon }_{0}F$

Answer 1

The correct option is A ${\epsilon }_{r}F$

Dielectric constant of medium $={\epsilon }_r$
Force in the medium $=F_m$
The electric force between point charges in the presence of medium is given by
$F_m=\frac{F_{air}}{{\epsilon }_r}$
$F_{air}=F_m\times {\epsilon }_r=F\cdot {\epsilon }_r$.