Tubes and slices: a new way of teaching the principles of electric and magnetic fields

To overcome the difficulty experienced by students in visualizing electric and magnetic fields, a graphical method is proposed using a personal computer to display the field. It is argued that the natural structure of such fields is given by tubes of flux and/or slices bounded by equipotentials. These two descriptions are shown to provide upper and lower bounds for the system energy and for the equivalent circuit parameters describing that energy. The calculations are extremely simple and can be used by the student in an interactive mode. The method is, therefore, suitable as a design tool. It can also be usefully combined with a finite element calculation to improve the accuracy. A suitable computer package called TAS is briefly described