Question

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

• A. increases K times
• B. remains unchanged
• C. decreases K times
• D. increases $K^{-1}$ times

Answer 1

Answer: (C)

In air the force of attraction between two charges is $F_a=\frac{1}{4\pi {ϵ}_0}\frac{q_1{q}_2}{r^2}$
In dielectric medium the force of attraction between two charges is $F_d=$

\frac{1}{4 \pi K \epsilon_{0}} \frac{ q _{1} q _{2}}{ r ^{2}}=\frac{ F _{ a }}{ K }

Thus, force decreases K-times.