Experimental Study on a Condition of Rotating a Magnetic Ball by Applying the Pulse Magnetic Field

Abstract

This paper describes a simulative experiment using a large scale model of a twisting ball magnetic display. One hemisphere of the magnetic ball with the diameter of 6mm is magnetized to “North” and colored white. The other hemisphere is magnetized to “South” and colored black. The electromagnet generates the pulse magnetic field to rotate the magnetic ball by applying the pulse current. As a half rotation is made, the visible color of the ball is inversed. Relationship between the pulse width and the amplitude of the current is studied. As the amplitude of the current is increased, the probability of rotation is increased. Finally the probability reaches 100%. As the pulse width is increased, the amplitude to rotate the ball is decreased. As a result, the following relationship is obtained. As the pulse width becomes one tenth, the correspondent amplitude for rotating the ball becomes double. For example, if the pulse width is 500ms, the correspondent amplitude is 0.3A. And as the pulse width is 50ms, the correspondent amplitude is 0.6A. This relationship is expressed by the following equation. In/I0 = (Tn/T0)−log2, where In/I0 is the ratio of the amplitude compared with the initial amplitude and Tn/T0 is the ratio of the pulse width compared with the initial pulse width. It is also found that as the pulse width becomes one tenth, the correspondent electric energy becomes 0.4 times. This relationship is expressed by the following equation. Wn/W0 = (Tn/T0)−log0.4 = (Tn/T0)log2.5, where Wn/W0 is the ratio of the electric energy. As a result it is found that a current with shorter width and higher amplitude is more effective than a current with longer pulse width and lower amplitude.