Question

I have an insulator with dielectric constant k. If I place it in a region in vacuum with a field E. Then the net field inside the dielectric will be?

• A. $Ek$
• B. $\frac{E}{k}$
• C. $\frac{E}{k^2}$
• D. $E{k}^2$

Answer 1

The correct option is B $\frac{E}{k}$

Electric field due to a charge Q in vacuum is
$E=\frac{1}{4\pi {\epsilon }_0}\frac{Q}{r^2}$
Now if we change the medium to a new one with a dielectric constant (relative permittivity) k, the equation now becomes.
$E^{\prime }=\frac{1}{4\pi k{\epsilon }_0}\frac{Q}{r^2}$
$E^{\prime }=\frac{E}{k}$