ABSTRACT
The magnetostatic field (Chapter 26) like the electrostatic field (Chapter 24) is specified by three related vectors, viz. the magnetic field, induction, and polarization (Section 26.1); there are differences in the constitutive properties relating them that are specified by the magnetic permeability and susceptibility (Section 26.2). These differences ultimately arise from Maxwell’s equations: the electric (magnetic) field is created by electric charges (currents), and is analogous to the potential flow due to source/sinks (vortices), leading (Section 26.3) to a Coulomb (Biot-Savart force) that acts along (across) the relative position vector. In follows that magnetic multipoles interchange the field lines and equipotentials of electric multipoles (Section 26.4), and reverse the alternating and identical images on planes (Section 26.5), corners (Section 26.6), and cylinders (Section 26.7). Bearing in mind these differences of detail, the general methods are similar, for example, for a cylindrical interface between media with distinct magnetic permeabilities (Section 26.8) and the generation of the field by multipole distributions with finite or infinite extent (Section 28.9). The two building blocks to be combined in the electromagnetic phenomena like waves and circuits are best studied separately in electrostatics (Chapter 24) and magnetostatics (Chapter 26). The latter have analogies and differences, for example, the magnetic field is always solenoidal and the electric field is irrotational in steady conditions.
