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)

decreases K times

Answer 2

In air the force of attraction between two charges is $F _{ a }=\frac{1}{4 \pi \epsilon_{0}} \frac{ q _{1} q _{2}}{ r ^{2}}$
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.