Low-Frequency Image Theory for a Current Dipole in Front of a Permeable Sphere

摘要

Image theory, previously developed for a low-frequency current source in front ofa dielectric sphere, is formulated for the magnetically permeable sphere. The low-frequency image source corresponding to an electric dipole outside the sphere arises only when the orientation of the dipole is tangential to the surface of the sphere. Two alternative image representations are developed. One is a combination of a magnetic strip current and a bifilar magnetic line current, both flowing between the center of the sphere and the Kelvin inversion point on the axis connecting the sphere and the dipole. The other is a combination of a magnetic strip current and an electric strip current flowing orthogonally to each other.