Alexander Fufaev

Formula: Coulomb's Law for Two Point Charges

Coulomb's Electric Force as a Function of the Distance Between the Charges

Force

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

Electric charge

Unit
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

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

Distance

Unit
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

Unit
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

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