coulombkraft

Coulombkraft, or the Coulomb force, is the electrostatic interaction between electric charges. The magnitude between two point charges q1 and q2 separated by a distance r is F = k |q1 q2| / r^2, where k is Coulomb's constant, k = 1/(4π ε0) ≈ 8.9875×10^9 N m^2/C^2 in vacuum. The force is directed along the line joining the charges and is repulsive for like charges and attractive for opposite charges.

The vector form is F12 = k q1 q2 / r^2 r_hat, where r_hat points from charge 2 to charge 1. In a homogeneous medium with permittivity ε = ε0 εr, the force becomes F = q1 q2 /(4π ε r^2). The corresponding electric potential energy is V(r) = k q1 q2 / r.

Coulombkraft underpins many phenomena in physics and chemistry, including the structure of atoms, ionic bonding, and the behavior of electrostatic fields in devices such as capacitors and sensors. It also explains screening and dielectric effects in materials, where the effective strength is reduced by the medium's permittivity.

Historical note: Charles-Augustin de Coulomb established the inverse-square form in the 1780s using a torsion balance, forming the basis of classical electrostatics. While Coulomb's law describes stationary or slowly varying charges, more complete descriptions in electrodynamics account for moving charges and magnetic effects, and quantum electrodynamics describes interactions at the particle level.