When air is replaced by a dielectric medium of constant K, the maximum force of attraction between two charges, separated by a distance: [AIPMT 1999]

[a] ACCORDING to Coulomb's LAW, force between two CHARGES is directly PROPORTIONAL to product of charges and inversely proportional to square of distance between them. Thus, \[F=\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{{{q}_{1}}{{q}_{2}}}{{{r}^{2}}}\] (i) Here, \[\frac{1}{4\pi {{\varepsilon }_{0}}}=\] proportionality constant. If a dielectric medium of constant K is placed between them, then new force between them, \[F'=\frac{1}{4\pi {{\varepsilon }_{0}}K}.\frac{{{q}_{2}}{{q}_{2}}}{{{r}^{2}}}\] (ii) Dividing Eq. (ii) by Eq. (i), we have \[\frac{F'}{F}=\frac{1}{K}\] or \[F'=\frac{F}{K}\] Thus, new force decreases K times.