Question

Two charged spheres separated at a distance d exert a force F on each other. If they are immersed in a liquid of dielectric constant 2, then the force (if all conditions are same) is :

• A. F/2
• B. F
• C. 2F
• D. 4F

Answer 1

The correct option is A F/2

$\text{Step 1: Force exerted between two charged spheres in vacuum}$

Let $q_1$ and $q_2$ be the charges on spheres.

Considering the spheres to be the point charges:

Using Coulomb's law, $F=\frac{1}{4\pi {\in }_0}\frac{q_1{q}_2}{d^2}$

$\text{Step 2: Force exerted between two charged spheres in medium}$

$F^{\prime }=\frac{1}{K}\frac{1}{4\pi {\in }_0}\frac{q_1{q}_2}{d^2}$

$\Rightarrow F^{\prime }=\frac{F}{K}=\frac{F}{2}$

Hence, Option A is correct.