In the early days of teaching electric circuits and electromagnetics, the question of which system of units to use was one facing the instructor and the textbook writer. At most schools, as at the University of Illinois, the Department of Electrical Engineering grew out of the Department of Physics. The tendency was to use the systems of units used in beginning physics courses. These systems included electrostatic units (ESU), centimeter-gram-second units (CGS), and Gaussian, which is a combination of ESU and CGS. On the other hand, in the field of electric circuits using volts, amperes, and ohms, the meter-kilogram-second (MKS) is the logical choice, with only the question of rationalization (where to introduce the factor 4p) left for debate. The unfortunate beginning student was faced with the difficult and confusing task of learning two or three systems of units while trying to understand the basic theory.

Fortunately, at the University of Illinois, the Department of Physics was in the College of Engineering (a rather unusual arrangement), so the question of which system to use was resolved more easily than at other schools where physics was in liberal arts. When members of the Department of Physics insisted on continuing to teach freshman physics in the old familiar systems, the head of electrical engineering, John D. Ryder, proposed that the Department of Electrical Engineering should be allowed to teach its own physics courses using the MKS system. The result was an immediate decision by the head of physics that, henceforth, all beginning physics courses would use the MKS systems.

Although the University of Illinois became one of the first schools to use the MKS system in the beginning physics courses, it did not follow that advanced courses in physics and mathematics would change their unit systems. Indeed, many advanced theory courses are taught with a total disregard for the numerical factors that depend on the system of units used. This point was brought home to a young electrical engineering faculty member who audited an advanced course in electromagnetic theory. He said it did not bother him too much that the professor put the dielectric constant e0=1; nor did it worry him to put the permeability of free space µ0=1; and because the velocity of light is given by c=1/µ0e0 it seemed reasonable to put c=1. But when the professor put the rationalization factor 4p equal to 1, the young faculty member felt it was really a bit much.

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Centennial History of the Department of ECE
University of Illinois at Urbana-Champaign
Electrical and Computer Engineering Department
ECE Publications