Elektrostatike

Elektrostatike, or electrostatics, is the branch of physics that studies electric charges at rest and the forces and fields they produce. It covers how stationary charges interact, how electric fields are created, and how these fields relate to electric potential.

A central principle is Coulomb's law, which states that the force between two point charges q1 and q2 separated by a distance r is F = k q1 q2 / r^2, where k is 1/(4π ε0) in vacuum. The electric field E is the force per unit charge, so a test charge q experiences F = qE, and for a point charge q0, E = k q0 / r^2 in the radial direction. The electric potential V is related to the field by E = -∇V, and equipotential surfaces are locations of constant V.

The superposition principle applies: the total field is the vector sum of contributions from all charges. Gauss's law provides a powerful tool for relating the electric field to enclosed charge: ∮ E · dA = Qenc/ε0. In media, the description is refined with the displacement field D = ε0 E + P, and Gauss's law becomes ∮ D · dA = Qenc. Boundary conditions at interfaces and the role of permittivity ε = ε0 εr are important for problems with dielectrics.

Capacitance concepts arise naturally: for conductors at constant potential, C = Q/V, and the stored energy is U = 1/2 C V^2. Common configurations include parallel-plate and coaxial capacitors, with dielectrics influencing energy storage.

Elektrostatike underpins many applications, such as electrostatic precipitators, printing and copying technologies, and coating processes, while its theoretical framework forms the quasi-static limit of electromagnetic theory, valid when charges move slowly enough that radiation can be neglected.