Interaction of cylindrical magnet with semi-space

V. Vorohobov

Institute of Physics, University of Latvia, 32 Miera str., Salaspils, LV-2169, Latvia

Abstract
An approach for calculation of the attraction force of permanent magnet to semi-space of a magnetizable material is developed. Simple analytical relations are proposed for engineering purposes, which guarantee 1%-10% accuracy at any distance ranging 0 to +∞. This formula can be used for evaluation of a holding force created by the magnet, for measuring the magnetic moment and quality control of magnetization of cylindrical magnets, and for measuring the magnetic permeability μ of magnetic fluids and other substances, where μ in value is close to unity. Measurements of some magnetic fluid samples were taken. It is found experimentally that the accuracy is better when there is a standard gap between the magnet and the sample, which is equal to the radius of the magnet. Experiments were carried out with magnets available on the market, for which a non-uniformity of magnetization about 5%-20% was found by measuring the sticking force in direct contact. A balance, which is able to measure very dissimilar forces, was created. Tables 1, Figs 8, Refs 12.