where r is the distance between two point charges q₁ and q₂,
k = 9 × 10⁹ N·m²/C², and F is in newtons.

Note that whether an electric force F is considered positive or negative depends on the coordinate system being used. The signs of the charges only specify whether the force between the charges is attractive or repulsive. For instance, having one positive charge and one negative charge does not mean the force F between them is negative, only that it is attractive.

Last modified on February 13, 2002