Сила, действующая на немагнитное тело в магнитной жидкости

Abstract

The paper reports the results of measuring the forces acting on an aluminum cylinder (a nonmagnetic body) immersed into a magnetic fluid under the action of external uniform magnetic field. The cause of the appearance of ponderomotive forces are inhomogeneous fields created by the liquid itself. Since the demagnetizing field is maximal at the ends of the cavity and minimal at its center, any nonmagnetic body must be pushed out of the central region and pressed against the ends of the cavity by the magnetic part of the hydrostatic pressure. It was obtained from the experiment that the ponderomotive force is dependent on the displacement of the aluminum cylinder relative to center of the cavity and on the strength of the external field. As was expected, the ponderomotive force increases with the field strength growth. This force is maximal near the ends of the cavity with a magnetic fluid due to the greatest inhomogeneity of the field, and is always minimal in the center of the cavity. An unexpected result is the discovery of large forces repelling aluminum cylinders from the ends of the cavity in the region of small gaps (~ 2 mm) between the cylinder and the ends. The possible reasons for this anomaly are discussed: the non-Newtonian properties of the magnetic fluid and the concentration of magnetic field lines near the edges of the cylinder.