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

Answer 1

Answer: (C)

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.