Abstract :
The present paper treats of the following matters: 1. Simplification of the physical formula for magnetic attraction, 2. Definition of magnetic reluctance when the magnetic field is bounded by non-equipotential surfaces, 3. Calculation of the virtual variation in magnetic reluctance due to any displacement of the limiting surfaces, 4. Demonstration of the theorem that the magnetic attraction between two ferromagnetic bodies depends only upon their common magnetic fluxes ?? and upon the virtual gradient of its air-reluctances Ro, and that the formula Fl = ??2/8 ?? ?? Ro/??l which gives the altraction along any given direction l is as general and as exact as the formulas of physics, 5. Direct deduction of magnetic attraction from the lines of magnetic flux depicted by a magnetic figure without resorting to the components of the magnetic field. The method used is developed by the application of the well-known principles of the potential energy function to the magnetic flux in the air-gap. Paths for the magnetic flux are established across the air-gap between the two ferromagnetic surfaces bounding the air-gap, by decomposing the magnetic flux into elemental tubes of magnetic force, the envelopes of which enclose spaces in which the flux is constant. The element of boundary-surface intersected by each elemental tube at the two boundary-surfaces encloses an equal number lines of magnetic flux, irrespective of the magnetic density at these points.
