Magnetfeldkreis

Magnetfeldkreis is a descriptive term used in German-language physics to refer to the circular arrangement of magnetic field lines around magnetic sources such as electric currents or moving charges. The concept emphasizes the circular, closed nature of magnetic field lines, which form continuous loops rather than having beginning or end points.

A classic example is the magnetic field produced by a long straight current-carrying wire. The magnetic field forms concentric circles around the wire, with the field strength decreasing with distance from the wire according to B = μ0 I / (2π r). In other geometries, such as around a finite loop of current or within a magnetized material, the field lines still close on themselves, creating complex but closed paths through space.

The idea of a magnetfeldkreis is consistent with the fundamental property of magnetic fields: there are no magnetic monopoles, and the divergence of B is zero (div B = 0). Consequently, magnetic field lines have no starting or ending points and must form loops. Ampère’s law relates the line integral of B around a closed path to the current enclosed, reinforcing the loop-like nature of the field in practical situations.

In materials, microscopic currents due to electron motion and magnetization generate similar closed-field patterns, though the exact geometry depends on the material’s structure and magnetic domain configuration. The term magnetfeldkreis is primarily a pedagogical tool to visualize the solenoidal character of magnetic fields rather than a separate physical entity.

Overall, the magnetfeldkreis highlights the circular, continuous nature of magnetic fields as understood in classical electromagnetism.