Coulomb’s Law describes the strength of the electrical force between two charged objects. The formula is F = k (q₁ q₂/r²), where k is a constant equal to 9.0 x 10⁹ Nm²/C² (newton-meters squared per coulombs squared). The charges q₁ and q₂, measured in coulombs, represent the charges on the objects that cause the force F, measured in newtons. Finally, r is the distance between the centers of the two charged objects. A negative force is an attractive force, while a positive force is repulsive.