## Conceptual Physics (12th Edition)

Coulomb's Law guides our answers, in particular, the inverse-square nature of the law. The force is inversely proportional to the square of the distance. $$F = k \frac{q_{1} \; q_{2}}{d^{2}}$$ If the two charges are brought closer together, dividing their separation distance by a factor of 2, the force is multiplied by a factor of 4. If the two charges are brought closer together, dividing their separation distance by a factor of 4, the force is multiplied by a factor of 16. If the two charges are moved farther apart, multiplying their separation distance by a factor of 4, the force is divided by a factor of 16.