Unwanted inductances

Chapter Unwanted inductances

Teach Yourself Electricity and Electronics Third Edition Book
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Summary of Contents

Teach Yourself Electricity and Electronics Third Edition Book

  • inductance will become larger as the frequency increases. At a certain limiting fre-quency, the inductance becomes infinite. Above that frequency, the line becomes ca-pacitive instead. You’ll learn about capacitance shortly.A detailed discussion of frequency, transmission line type and length, and induc-tance is beyond the level of this book. Texts on radio engineering are recommended forfurther information on this subject.Unwanted inductancesAny length of wire has some inductance. As with a transmission line, the inductance ofa wire increases as the frequency increases. Wire inductance is therefore more signifi-cant at radio frequencies than at audio frequencies.In some cases, especially in radio communications equipment, the inductanceof, and among, wires can become a major bugaboo. Circuits can oscillate when theyshould not. A receiver might respond to signals that it’s not designed to intercept. Atransmitter can send out signals on unauthorized and unintended frequencies. Thefrequency response of any circuit can be altered, degrading the performance of theequipment.Sometimes the effects of stray inductance are so small that they are not impor-tant; this might be the case in a stereo hi-fi set located at a distance from other elec-tronic equipment. In some cases, stray inductance can cause life-threateningmalfunctions. This might happen with certain medical devices.The most common way to minimize stray inductance is to use coaxial cables be-tween and among sensitive circuits or components. The shield of the cable is connectedto the common ground of the apparatus.QuizRefer to the text in this chapter if necessary. A good score is 18 correct. Answers are inthe back of the book.1. An inductor works by:A. Charging a piece of wire.B. Storing energy as a magnetic field.C. Choking off high-frequency ac.D. Introducing resistance into a circuit.2. Which of the following does not affect the inductance of a coil?A. The diameter of the wire.B. The number of turns.C. The type of core material.D. The length of the coil.3. In a small inductance:A. Energy is stored and released slowly.Quiz195