Induced Magnetic Field Due to the Motion of a Conducting Sphere.

摘要

Integral formulae are obtained for the induced magnetic field (internal and external) and the induced electric current (internal) associated with the arbitrary translational motion of a spherical body of low electrical conductivity through a nonconducting region in which there exists an arbitrary inhomogeneous unsteady externally-applied magnetic field. The quasistationary approximation is used, and induced disturbances are calculated to first order in the magnetic Reynolds number. Numerical methods are required for evaluation of the integrals. Expressions for the induced magnetic field far away from the sphere and for the induced magnetic field and induced current near the center of the sphere are presented as limiting cases. The method is applied to a determination of the disturbances associated with motion of the sphere: (1) along the axis of a steady cusped field, (2) through an unsteady uniform field, and (3) along the axis of the field of a circular current loop or across the field due to two circular pole pieces. (Author)