Answer:
3.2 × 10⁻⁸ N.
Explanation:
By Coulomb's Law, the magnitude of the electromagnetic force between two point charges is inversely proportional to the square of their separation, [tex]r[/tex]. In other words,
[tex]\displaystyle \frac{F_1}{F_2} = {\left(\frac{r_2}{r_1}\right)}^{2}[/tex].
Final electromagnetic force:
[tex]\displaystyle F_2 = F_1 \cdot \left(\frac{r_2}{r_1}\right)^{2} = 8\times 10^{-9}\times \left( \frac{20}{10}\right)^{2} = 3.2\times 10^{-8}\;\text{N}[/tex].