The answer is "The force between two charges and the distance separating them".
Coulomb's Law is written as:
[tex]F=k \frac{q_1q_2}{r^2} [/tex]
In which [tex]F[/tex] is the force felt between two charges, [tex]q_1[/tex] is the charge of one particle, [tex]q_2[/tex] is the charge of the other particle, [tex]r[/tex] is the distance separating them, and [tex]k[/tex] is a constant.
