Formula: Coulomb's Law for Two Point Charges Force    Electric charge    Distance    Relative permittivity   

Formula: Coulomb's Law for Two Point Charges
Coulomb's Electric Force as a Function of the Distance Between the Charges
Distance Between Two Charges and their Electric Field


Electrostatic force (also called Coulomb force) is the attractive or repulsive electric force between two charges \( q_1 \) and \( q_2 \).

Electric charge

This charge is the property of the first charge carrier participating in the electrical interaction. Depending on the sign of the charge, the charge carrier repels or attracts other charge carriers. A proton (positive sign) attracts an electron (negative sign).

Electric charge

This charge is the property of the second charge carrier that participates in the electrical interaction.


The distance between the charges \( q_1 \) and \( q_2 \). The larger this distance is, the smaller is the electrostatic force between the charges.

Relative permittivity

This dimensionless quantity describes the medium in which the two charges are located. If the two charges are in vacuum then \( \varepsilon_{\text r} = 1 \). And, if they are in water, for example, then \( \varepsilon_{\text r} = 80 \). The greater the relative permittivity of the medium, the more this medium weakens the force between the charges.

Vacuum Permittivity

The vacuum permittivity is a physical constant that appears in equations involving electromagnetic fields. It has the following experimentally determined value: $$ \varepsilon_0 ~\approx~ 8.854 \, 187 \, 8128 ~\cdot~ 10^{-12} \, \frac{\mathrm{As}}{\mathrm{Vm}} $$

+ Perfect for high school and undergraduate physics students
+ Contains over 500 illustrated formulas on just 140 pages
+ Contains tables with examples and measured constants
+ Easy for everyone because without vectors and integrals

Learn more