Interparticle force measurements on ferromagnetic steel balls

Abstract

Interparticle force measurements have been performed upon various configurations of linear chains and planar layers of chrome steel balls immersed in a steady uniform applied magnetic field. These force measurements, made for particles in contact and at various separations, reveal that the attractive forces are enhanced in the case of particle chains parallel to the applied magnetic field and slightly decreased in the case of perpendicular layers. The magnetic saturation exhibited by the steel balls has only a modest effect on the force. Experimental data obtained for two-particle chains correlate reasonably well to force calculations based upon a linear multipolar expansion using a relative particle permeability value of μr=100. It is also found that data obtained with longer linear chains as well as with planar particle arrays do not deviate drastically from the predictions of the two-sphere problem.