Inductive reactance

Chapter Inductive reactance

Teach Yourself Electricity and Electronics Third Edition Book
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Summary of Contents

Teach Yourself Electricity and Electronics Third Edition Book

  • 13CHAPTERInductive reactanceIN DC CIRCUITS, RESISTANCE IS A SIMPLE THING. IT CAN BE EXPRESSED AS Anumber, from zero (a perfect conductor) to extremely large values, increasing withoutlimit through the millions, billions, and even trillions of ohms. Physicists call resistancea scalar quantity, because it can be expressed on a one-dimensional scale. In fact, dc re-sistance can be represented along a half line, or ray, as shown in Fig. 13-1.23113-1Resistance can be represented on a ray.Given a certain dc voltage, the current decreases as the resistance increases, in ac-cordance with Ohm’s Law, as you already know. The same law holds for ac through a re-sistance, if the ac voltage and current are both specified as peak, pk-pk, or rms values.Coils and direct currentSuppose that you have some wire that conducts electricity very well. What will happenif you wind a length of the wire into a coil and connect it to a source of dc, as shown inFig. 13-2? The wire will draw a large amount of current, possibly blowing a fuse or over-stressing a battery. It won’t matter whether the wire is a single-turn loop, or whether it’slying haphazardly on the floor, or whether it’s wrapped around a stick. The current willbe large. In amperes, it will be equal to IE/R, where I is the current, E is the dc volt-age, and R is the resistance of the wire (a low resistance).Copyright © 2002, 1997, 1993 by The McGraw-Hill Companies. Click here for terms of use.