Electric circuitry

Electrical Apparatus, Jun 1999 by Nailen, Richard L

Foundations of Electric Circuits. By J.R. Cogdell. Prentice-Hall, Inc., Englewood Cliffs, N.J. 07632; (800) 9477700. $35 (softbound). 386 pages.

Back in the days of Faraday or Tom Edison, nobody had ever heard of "electrons." When vacuum tube theory was developed, however, engineers realized that an electric current was a movement of electrons-whether cathode-to-plate inside a tube or within a solid conductorfrom negative pole to positive pole.

That simple concept didn't suit semiconductor theorists, however. Today's textbooks (like this one) distinguish between electron movement in one direction, and a "physical current" having the opposite direction of flow.

Rationalizations of this can become tortuous. Rather than attempt one, Cogdell, a professor at the University of Texas in Austin, simply states that "physical current" flows from positive to negative, without further explanation, as though it were a given. This may not be the best way of introducing students to fundamental concepts.

Readers getting past that sticking point will find good explanations of Kirchhoff's voltage and current laws, Thevenin's theorem, superposition, and other basics of circuit behavior. Series and parallel combinations of resistance, inductance, and capacitance are well covered. Several chapters deal with a-c phasors, sinusoids, and filter behavior. A brief look at delta-wye power systems follows. Worked examples and "what if" questions are provided throughout, and each chapter includes a useful glossary.-RLN