This law, formulated by Charles Augustin Coulomb, refers to the interaction forces (attraction and repulsion) between two punctual electric charges, that is, with negligible size and mass.
Recalling that, by the principle of attraction and repulsion, charges with opposite signs are attracted and with equal signs are repelled, but these interaction forces have equal intensity, regardless of the direction in which the vector describing them points.
What Coulomb's Law states is that The intensity of the electrical force of interaction between point loads is directly proportional to the product of the modules of each load and inversely proportional to the square of the distance between them.. That is:
Where the equation can be expressed by an equality if we consider a constant k, which depends on the medium where the loads are found. The most usual value of k is considered when this interaction happens in a vacuum, and its value is equal to:
Then we can write Coulomb's equation as:
To determine whether these forces are attractive or repulsive, the product of their loads is used, ie: