# Coulomb's law

Coulomb's law is a function developed in the 1780s by physicist Charles-Augustin de Coulomb. It explains how strong the force will be between two electrostatic charges. Electrostatic means electric charges without any motion.

## Direction This picture shows how Coulomb's Force act; similar charges pushing against each other and opposite charges attract each other

Let's think of two electric charges existing in an empty space. If the two charges are opposite, (+) and (-) charges for example, they will attract each other. And if two charges are both the same, both (+) or both (-) for example, they will push each other. This is similar to how magnets act, as N and S attract each other, and as N and N, S and S push each other.

This is because electric charges make an electric field. If two fields exist in the same space at the same time, then the two fields exert (~ put) force on each other. The force they make on each other is called 'Coulomb's force' or the electrostatic force. Coulomb's law explains how big the force will be.

## Scale

Coulomb's law explains the scale between two electric charges. The scale of electrostatic force follows the function below.

$F={K_{c}}{\frac {q_{1}q_{2}}{r^{2}}}$ Coulomb's law explains that the force scale F is relative to ratio of $q_{1},q_{2}$ ,${\frac {1}{r^{2}}}$ .

$q_{1}$ and $q_{2}$ are the scales of each electric charge. $r$ is the distance between the two electric charges. And $K_{c}$ has a certain value. It does not change relative to $q_{1}$ , $q_{2}$ or $r$ . While ${K_{c}}$ remains constant, when multiples of $q_{1}$ and $q_{2}$ become bigger, the electrostatic force will also get bigger. When the distance $r$ becomes bigger, the electrostatic force will become smaller by the ratio of ${\frac {1}{r^{2}}}$ .
The exact size of $K_{c}$ is {\begin{aligned}k_{c}&=8.987\ 551\ 787\ \times 10^{9}\\\end{aligned}} $\approx 9\times 10^{9}$ N m2 C−2 (or m F−1). This constant is called Coulomb's force constant or the electrostatic force constant.

## Inverse-square law

The relation between the force of pushing or pulling (F) and the distance between the particles ($r$ ) follows the Inverse-square Law. Inverse-square law means that when the distance $r$ grows bigger, the force gets weaker by the ratio ${\frac {1}{r^{2}}}$ . Gravitation, Electromagnetic radiation, and sound loudness also follow this law.