# Coulomb’s Law

If two charged particles have the charges $q_{1}$ and $q_{2}$ and of a distance $r$ apart, then they exert an Electric Force:

$F_{1 on 2}=−F_{2 on 1}=r_{2}kq_{1}q_{2} r_{q_{1}q_{2}} $ where

- $k$ is the Coulomb’s Constant
- $r$ is the unit vector pointing in direction from $q_{1}$ to $q_{2}$

Intuitively, the **direction of the force**:

- Two charges of equal sign repel each other
- Two charges of opposite sign attract each other

### Limitations

- Charged bodies must be very small compared to $r$ (infinitesimally small)
- Force must be inversely proportional to $r_{2}$