Coulomb's Law

On the topic of how electric charges dynamically interact with each other, it is in our best interests to be able to quantify this. While we can figure out the direction of an electric force through the signs of the charge, Coulomb's Law can tell us what the magnitude of the electrical force between two objects is, through the following equation:

As you notice, the constant k is Coulomb's constant, similar to the universal gravitational constant. As you can notice by the denominator, Coulomb's law is an inverse-square law and is proportional to the magnitude of the product of the two charges involved, measured in Coulombs(C). Newton's Third Law reaction force to the electric force exerted on an object q1 by an object q2 is the force q1 exerts on q2. Remember, Coulomb's law only gives the magnitude of the electrostatic force between two charged objects. You must find the direction of the force through the signs of the objects' charges and their relative positions to each other.