Coulomb's law

Statement

$F = k\dfrac{|q_1 q_2|}{r^2}$ — the interaction force between two point charges $q_1, q_2$ separated by $r$, with $k \approx 9 \times 10^9\ \text{N·m}^2/\text{C}^2$.

Why is it true?

Like charges repel, unlike charges attract; the force falls off with the square of distance, the same form as Newtonian gravity.

Topics that use this theorem

Step-by-step proofs