Question

What is the force between two small charges of $2\times {10}^{-7}C$ and $3\times {10}^{-7}C$ placed 30 cm apart in air?

Answer 1

$F=\frac{1}{4\pi {ϵ}_0}\frac{q_1{q}_2}{r^2}$
$=9\times {10}^9\times \frac{(2\times {10}^{-7})(3\times {10}^{-7})}{(0.30{)}^2}$
$=6\times {10}^{-3}N$