Ampere's theorem (on the equivalence of the magnetic field of a current and a magnetic leaf)

Prior to the discovery of the magnetic field generated by currents, it was believed that the source of the field is special substances - northern and southern magnetism, interacting according to the Coulomb law. However, magnetic charges were not found. Ampere hypothesized that currents should be the only source of magnetic field. Ampere added molecular currents to the usual macroscopic currents. Subsequently, it was found out that these are moving electrons and nuclei. Thus, Ampère's theorem was formulated, relating non-existent magnetic charges and a magnetic field. ^[one]

The so-called magnetic sheets are layers of fictitious magnetic dipoles forming a double magnetic layer. It should be noted that magnetic dipoles are inextricable. In addition, magnetic dipoles can be considered elementary circuits with current. ^[2]

The essence of the theorem was as follows: Let current I flow along a closed circuit on surface S. Then we can divide the surface into arbitrarily small sections dS and imagine that each section has its own currents I. Due to the superposition, the magnetic field created by such currents is equivalent to the field created by the general circuit S. On the other hand, each circuit is the equivalent of a magnetic dipole with its own dipole moment. That is, the field can be considered as generated by pairwise coupled magnetic charges. ^[3]

• Dipole (electrodynamics)
• Magnetic monopole

• - Ampere's theorem in the encyclopedia academician
• - Ampere's theorem in the scientific network Nature.Web
• - Ampere's theorem in a physical encyclopedia