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

The Correct Option is C

To determine the effect of introducing a dielectric medium on the force of attraction between two charges, we need to refer to Coulomb's law. The force of attraction or repulsion between two point charges in a vacuum is given by:

F = \frac{{k \cdot |q_1 \cdot q_2|}}{{r^2}},

where F is the force, k is Coulomb's constant, q_1 and q_2 are the magnitudes of the charges, and r is the distance between them.

When a dielectric medium with a dielectric constant K is introduced between the charges, the effective force F' is modified by the medium:

F' = \frac{{F}}{{K}}.

This means that the force between the charges decreases by a factor of K when a dielectric is inserted. Therefore, the new force of attraction becomes:

F' = \frac{{k \cdot |q_1 \cdot q_2|}}{{K \cdot r^2}}.

Given the options:

• increases K times
• remains unchanged
• decreases K times
• increases K^{-1} times

The correct answer is decreases K times, which aligns with the expression \frac{F}{K}. Thus, when a dielectric medium is introduced, it reduces the force of attraction between the charges by a factor of K.