CGPET 2019 Solved Paper

Let distance between two small spheres with constant charge is r as shown in figure.
According to the Coulomb's law, the force between the spheres in air is given by
Fair =

1

4πε0

q2

r2

.......(i)
Force between the spheres in medium is given by
Fmedium=

1

4πε0k

q2

r2

.......(ii)
From Eqs. (i) and (ii), we get

Fair

Fmedium

=

k

1

⇒Fair :Fmedium =k:1