Question

If the distances between two charges becomes double then the electrostatic forces between them will be:

• A. 2 times
• B. 4 times
• C. \frac{1}{4} times
• D. \frac{1}{2} times

Answer 1

Answer: (C)

\frac{1}{4} times

Answer 2

The electrostatic force between two point charges is given by Coulomb's Law:

$F = k \frac{q_1 q_2}{r^2}$

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.

If the distance $r$ is doubled to $2r$, the force changes by a factor of $1/(2r)^2 = 1/(4r^2)$, which means the new force is $\frac{1}{4}$ times the original force.