Introduction: If you've ever rubbed a balloon against your hair and put it against a wall, you'll notice that it sticks to the wall. This is a real-world application of what is known as Coulomb's Law, a law that describes the interactions between electrically-charged particles. These forces can be attractive or repulsive, depending on the sign of the electrostatic force shown in the equation below that represents Coulomb's Law:

`F_e = {kq_1q_2}/{r^2}`,

where `F_e`=electrostatic force, `k="electrostatic constant"`, `q_1`=charge of the first particle, `q_2`=charge of the second particle, and r=distance between the two particles

In general, when the distance between the particles increases, the electrostatic force between the particles decreases. The sign, on the other hand, affects whether the particles attract or repel one another. Generally, particles with opposite charges will attract one another, whereas particles with like charges will repel one another. In chemistry, Coulomb's law is generally used to calculate the energy involved in an ionic bond. The fact that particles with opposite charges attract one another helps to explain the electrostatic attraction between ions in an ionic bond, as a positive cation and a negative anion will attract one another.