Feldkraft

Feldkraft, in physics terminology, denotes a force that arises from a field, rather than from direct contact between objects. In a field-based description, a field assigns a quantity to every point in space (a vector for a vector field, a scalar for a scalar field). A test particle experiences a force F that depends on the local field and the particle's properties.

The most familiar examples are gravitational, electric, and magnetic fields. A body of mass m in a gravitational field with acceleration g experiences F = m g. A charge q in an electric field E experiences F = q E, and a moving charge in a magnetic field B experiences a force F = q v × B. In electromagnetism these contributions combine as the Lorentz force F = q(E + v × B). The electric and gravitational fields are conservative in static situations, allowing the use of potential energies.

Field forces are action-at-a-distance in the sense of being transmitted through space by the field, rather than through direct contact. They propagate changes at or below the speed of light, consistent with special relativity. In classical physics they can be described by potentials and field equations; in general relativity gravity is described as spacetime curvature rather than a conventional force acting through a field.

Terminology: Feldkraft is used in German-language texts but is less common than Kraftfeld, which more often denotes the field itself rather than the force. Nevertheless, Feldkraft is understood as the force resulting from a field.