Question

Two point charges $+4C$ and $+6C$ repel each other with a force F. If a charge $-5C$ is given to each of these charges, the force becomes:

• A. repulsive force of $\frac{F}{24}$
• B. attractive force of $\frac{F}{24}$
• C. repulsive force $24F$
• D. attractive force $24F$

Answer 1

The correct option is B attractive force of $\frac{F}{24}$

$\Rightarrow GivenF=\frac{K\left(4\right)\left(6\right)}{r^2}$
Initially as both charges have similar sign there exist repulsion force when $-5C$ is given the charges become opposite and attract each other.
$F_{new}=\frac{K(-1)\left(1\right)}{r^2}$

$\frac{F_{new}}{F}=\frac{\frac{-K}{r^2}}{\frac{K\times 24}{r^2}}$

$F_{new}=-\frac{F}{24}$

(negative sign here implies the attractive nature of force)