Question

In Coulomb's law, the constant of proportionality K has the units :

• A. $N$
• B. $N^2$
• C. $N{C}^2/m^2$
• D. $N{m}^2/C^2$

Answer 1

The correct option is D $N{m}^2/C^2$

By Coulomb's law, the force between the charges is $F=\frac{K{q}_1{q}_2}{r^2}$ where $r$ is the distance between them.

So, $K=\frac{F{r}^2}{q_1{q}_2}=\frac{N{m}^2}{C^2}$

(Unit of force $F$ is $N$, unit of distance is $m$ and unit of charge is $C$)