Basic DC circuits

Chapter Basic DC circuits

Teach Yourself Electricity and Electronics Third Edition Book
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Summary of Contents

Teach Yourself Electricity and Electronics Third Edition Book

  • 4CHAPTERBasic dc circuitsYOU’VE ALREADY SEEN SOME SIMPLE ELECTRICAL CIRCUIT DIAGRAMS. SOME OFthese are the same kinds of diagrams, using the same symbols, that professional tech-nicians and engineers use. In this chapter, you’ll get more acquainted with this type ofdiagram. You’ll also learn more about how current, voltage, resistance, and power arerelated in direct-current (dc) and low-frequency alternating-current (ac) circuits.Schematic symbolsIn this course, the plan is to familiarize you with schematic symbols mainly by gettingyou to read and use them “in action,” rather than by dryly drilling you with them. Butit’s a good idea now to check Appendix B and look over the various symbols. Some ofthe more common ones are mentioned here.The simplest schematic symbol is the one representing a wire or electrical conduc-tor: a straight, solid line. Sometimes dotted lines are used to represent conductors, butusually, dotted lines are drawn to partition diagrams into constituent circuits, or to in-dicate that certain components interact with each other or operate in step with eachother. Conductor lines are almost always drawn either horizontally across, or verticallyup and down the page, so that the imaginary charge carriers are forced to march in for-mation like soldiers. This keeps the diagram neat and easy to read.When two conductor lines cross, they aren’t connected at the crossing point unlessa heavy, black dot is placed where the two lines meet. The dot should always be clearlyvisible wherever conductors are to be connected, no matter how many of them meet atthe junction.A resistor is indicated by a zig-zaggy line. A variable resistor, or potentiometer, is in-dicated by a zig-zaggy line with an arrow through it, or by a zig-zaggy line with an arrowpointing at it. These symbols are shown in Fig. 4-1.A cell is shown by two parallel lines, one longer than the other. The longer line rep-resents the plus terminal. A battery, or combination of cells in series, is indicated by 65Copyright © 2002, 1997, 1993 by The McGraw-Hill Companies. Click here for terms of use.