Electricity and Magnetism

Abstract

Electromagnetism is an important subject in today’s physics. The number of textbooks on electromagnetism is much larger than those on other subjects. This is because abstract concepts are frequently used and therefore it is not easy for students to come to a complete understanding of electromagnetism, although various phenomena are concisely described with mathematics. For this reason many textbooks have been published to assist students to understand electromagnetism better. Why, then, is a new textbook on electromagnetism necessary now? Electromagnetism is a classical subject that was almost completely formulated in the nineteenth century. However, concerning its theoretical description, there is still room for further progress. In addition, textbooks are required to describe their topics adequately within a limited space. Therefore, there is also room for improvement in textbooks from the technical point of view. In principle, there is a beautiful formal analogy between static electric and magnetic phenomena, as will be shown in this textbook. However, the analogy is not necessarily perfect in existing textbooks because of the lack of an important concept. Electric materials are classified into conductors and dielectric materials, but only magnets are studied as magnetic materials. While it is known that electric phenomena in dielectric materials and magnetic phenomena in magnets are analogous to each other, no one has discussed magnetic materials that correspond to electric conductors. However, we have to note superconductors. In a superconductor a current flows on its surface to shield the inside against an external magnetic field, so that the magnetic flux density B is zero in the superconductor. This is analogous to the electric phenomenon of a conductor in an external electric field. That is, an electric charge appears on its surface to shield the inside against an external electric field, so that the electric field E is zero in the conductor. This is one of the remarkable analogies in the present E–B analogy.