Chapter Resistors

Teach Yourself Electricity and Electronics Third Edition Book
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Summary of Contents

Teach Yourself Electricity and Electronics Third Edition Book

  • 6CHAPTERResistorsAS YOU’VE ALREADY SEEN, ANY ELECTRICAL DEVICE HAS SOME RESISTANCE; none is a perfect conductor. You’ve also seen some examples of circuits containing com-ponents designed to oppose the flow of current. This chapter more closely examines resistors—devices that oppose, control, or limit electrical current.Why, you might ask, would anyone want to put things into a circuit to reduce thecurrent? Isn’t it true that resistors always dissipate some power as heat, and that this in-variably means that a circuit becomes less efficient than it would be without the resis-tor? Well, it’s true that resistors always dissipate some power as heat. But resistors canoptimize the ability of a circuit to generate or amplify a signal, making the circuit maxi-mally efficient at whatever it is designed to do.Purpose of the resistorResistors can play any of numerous different roles in electrical and electronic equip-ment. Here are a few of the more common ways resistors are used.Voltage divisionYou’ve already learned a little about how voltage dividers can be designed using resis-tors. The resistors dissipate some power in doing this job, but the resulting voltages areneeded for the proper biasing of electronic transistors or vacuum tubes. This ensuresthat an amplifier or oscillator will do its job in the most efficient, reliable possible way.BiasingIn order to work efficiently, transistors or tubes need the right bias. This means that thecontrol electrode—the base, gate, or grid—must have a certain voltage or current. Net-works of resistors accomplish this. Different bias levels are needed for different types 99Copyright © 2002, 1997, 1993 by The McGraw-Hill Companies. Click here for terms of use.