Point charge

A point charge is an idealized electric charge concentrated at a single location, with no spatial extent. It models charged objects when their size is negligible relative to the distances involved.

Coulomb's law: The law giving the electrostatic force between two stationary point charges as proportional to their product and inversely proportional to distance squared. It gives the force between point charges directly from their charges and separation.
Electric charge: A fundamental property of matter that gives rise to electric interactions and is measured in coulombs. A point charge is the idealized spatial placement of this property.
Electric dipole: A system of two equal and opposite charges separated by a distance. It is the simplest finite arrangement built from point charges.
Continuous charge distribution: A model in which electric charge is spread continuously through a line, surface, or volume. It replaces the single localized source with charge spread across space.
Electric field: A vector field that assigns the electric force per unit positive test charge at each point in space. The point charge generates a radial field whose magnitude decreases with distance squared.
Electrostatics: The study of electric charges at rest and the electric fields and forces they produce. Point charges are basic sources in the static-charge models of this field.
Multipole expansion: A method for approximating a distant field by terms representing a source's total charge, dipole moment, and higher moments. It treats localized charge distributions through point-like contributions at long range.
Finite-size charge distribution: A model that accounts for charge occupying a spatially extended object or region. It becomes necessary when an object's dimensions cannot be neglected.
Electric potential: Electric potential is electric potential energy per unit charge at a location in an electric field. A point charge produces a potential that varies inversely with distance.
Coulomb: The coulomb is the SI unit of electric charge. It quantifies the charge assigned to an ideal point source.

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