Q. Two identical charges repel each other with a force equal to $10\ mg\ wt$ when they are $0.6\ m$ apart in the air. $g = \left( 10ms^{- 2} \right)$. The value of each charge is
A) $2\ mC$
B) $2 \times 10^{- 7}\ C$
C) $2\ nC$
D) $2\ \mu C$
Explanation
(d) $F = \frac{1}{4\pi\varepsilon_{0}}\ \frac{q_{1}q_{2}}{d^{2}}$
$\therefore\left( 10 \times 10^{- 3} \right) \times 10 = \ \frac{(9 \times 10^{9}) \times q^{2}}{(0.6)^{2}}$
$\Rightarrow q^{2} = 4 \times 10^{- 12}$
$\Rightarrow q = 2 \times 10^{- 6}C = 2\mu C$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.