Schaum's Outline of Basic Electricity

465 Pages·1983·7.768 MB·English

by  Milton Gussow

I . - w
SCHAUM’S OUTLZNE OF
THEORY AND PROBLEMS
OF
BASIC ELECTRICITY
MILTON GUSSOW, M.S.
Senior Engineer
Applied Physics Laboratory
The Johns Hopkins University
McGraw-Hill
New York San Francisco Washington, D.C. Auckland Bogota
Caracas Lisbon London Madrid Mexico City Milan
Montreal New Delhi San Juan Singapore
Sydney Tokyo Toronto
To Libbie, Myra, and Susan
MILTON GUSSOW is a senior engineer at Johns Hopkins University
Applied Physics Laboratory. He received his B.S. (1949) from the U.S.
Naval Academy, his B.S.E.E. (1956) from the U.S. Navy Postgraduate
School, and his M.S. (1957) from Massachusetts Institute of Technology.
He is an Adjunct Professor at American University and George
Washington University where he teaches courses in mathematics and
elkctrical engineering. Mr. Gussow was formerly Senior Vice President
for Education at the McGraw-Hill Continuing Education Center. He is
the author of over fifty technical papers.
Schaum’s Outline of Theory and Problems of
BASIC ELECTRICITY
Copyright 0 1983 by The McGraw-Hill Companies, Inc. All rights reserved. Printed in the United
States of America. Except as permitted under the Copyright Act of 1976, no part of this publication
may be reproduced or distributed in any form or by any means, or stored in a data base or retrieval
system, without the prior written permission of the publisher.
16 17 18 19 20 BAW 9 9
ISBN 0-03-025240-8
Sponsoring Editor, John Aliano
Consulting Editor, Gordon Rockmaker
Editing Supervisor, Marthe Grice
Production Manager, Nick Monti
Library of Congress Catalogjng in Publication Data
Gussow, Milton.
Schaum’s outline of theory and problems of basic
electricity.
(Schaum’s outline series)
Includes index.
1. Electricity. I. Title.
TK146.G974 1983 62 1.3‘02‘02 82-467 1
ISBN 0-07-025240-8
McGraw -Hill
E
A Division of 7-kM c#uw.Ha Companies
Preface
This book is intended as a basic text to cover the fundamentals of electricity
and electric circuits. It may be used by beginning students in high schools,
technical institutes, and colleges who have no experience in electricity.
Explanations and step-by-step solutions are deliberately detailed so that the
text can stand alone. Thus it also may be used as a home-study or reference
book. A knowledge of basic algebra and trigonometry is assumed. Designed to
provide a broad and deep background in the nature of electricity and the opera-
tion and application of electric circuits, the text uses numerous and easy-to-
follow examples accompanied by diagrams. Starting with the physics of electric
current flow, the book describes and analyzes both direct-current and alterna-
ting-current electric circuits, generators and motors, transformers, and measuring
instruments. To assure correlation to modern practice and design, illustrative
problems are presented in terms of commonly used voltages and current ratings,
covering circuits and equipments typical of those found in today’s electrical
systems.
There are several special features of this book. One is the use of the
International System of Units (SI) throughout. A second is the prolific use of
equation numbers for reference so that the reader will always know the source of
each equation used. Other features include simplified ways to solve problems on
three-phase transformer windings, series and parallel resonance, and RL and RC
circuit waveforms.
I wish to thank John Aliano, Gordon Rockmaker, and Marthe Grice of the
McGraw-Hill Book Company for their many constructive criticisms and con-
tinuing efforts to get this book published.
MILTON Gussow
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CONTENTS
..................................
Chapter 20 ELECTRICAL MEASUREMENTS 411
Basic Measuring Instruments ............................................. 411
Ammeters .............................................................. 411
Voltmeters ............................................................. 414
Ohmmeters ............................................................. 416
Multimeters ............................................................. 419
Alternating-Current Meters ............................................... 419
Wattmeters and Watthour Meters ......................................... 425
Analog Electronic Meters ................................................ 427
Digital Meters ........................................................... 429
..........................................................
INDEX 447
Contents
Chapter 1 THE NATURE OF ELECTRICITY ................................. 1
Structure of the Atom ................................................... 1
The Electric Charge ..................................................... 3
The Coulomb ........................................................... 4
The Electrostatic Field ................................................... 4
Potential Difference ..................................................... 5
Current ................................................................ 5
Current Flow ........................................................... 6
Sources of Electricity .................................................... 7
Direct and Alternating Currents and Voltages .............................. 8
..................
Chapter 2 ELECTRICAL STANDARDS AND CONVENTIONS 15
Units
Introduction ............................................................ 15
Metric Prefixes .......................................................... 15
Powers of 10 ........................................................... 16
Scientific Notation ....................................................... 20
Rounding Off Numbers .................................................. 20
Graphical Symbols and Electrical Diagrams
Schematic Diagram ...................................................... 27
One-Line Diagram ....................................................... 28
Block Diagram .......................................................... 31
Wiring Diagram ......................................................... 31
Electric Plan ............................................................ 31
3 .......................................
Chapter OHM’S LAW AND POWER 38
The Electric Circuit ..................................................... 38
Resistance .............................................................. 39
Fixed Resistors ......................................................... 39
Variable Resistors ....................................................... 40
Ohm’s Law ............................................................. 41
Electric Power .......................................................... 42
Horsepower ............................................................ 43
Electrical Energy ........................................................ 44
............................
Chapter 4 DIRECT-CURRENT SERIES CIRCUITS 50
Voltage. Current. and Resistance in Series Circuits .......................... 50
Polarity of Voltage Drops ................................................ 53
Conductors ............................................................. 53
Total Power in a Series Circuit ........................................... 57
Voltage Drop by Proportional Parts ....................................... 58
CONTENTS
........................
Chapter 5 DIRECT-CURRENT PARALLEL CIRCUITS 69
Voltage and Current in a Parallel Circuit ................................... 69
Resistances in Parallel ................................................... 71
Open and Short Circuits ................................................. 74
Division of Current in Two Parallel Branches .............................. 75
Conductances in Parallel ................................................. 75
Power in Parallel Circuits ................................................ 77
Chapter 6 BATTERIES ..................................................... 88
The Voltaic Cell ......................................................... 88
Series and Parallel Cells ................................................. 89
Primary and Secondary Cells ............................................. 90
Types of Batteries ....................................................... 90
Battery Characteristics ................................................... 94
............................................
Chapter 7 KIRCHHOFF’S LAWS 101
Kirchhoff’s Voltage Law (KVL) .......................................... 101
Kirchhoff’s Current Law (KCL) .......................................... 103
Mesh Currents .......................................................... 104
Node Voltages .......................................................... 106
Chapter 8 NETWORK CALCULATIONS ..................................... 116
Y and Delta Networks ................................................... 116
Superposition ........................................................... 120
Thevenin’s Theorem ..................................................... 122
Norton’s Theorem ....................................................... 124
Series-Parallel Circuits ................................................... 126
Wheatstone Bridge Circuit ............................................... 128
Maximum Power Transfer ................................................ 129
Line-Drop Calculations .................................................. 130
Three-Wire Distribution Systems .......................................... 131
........................
Chapter 9 MAGNETISM AND ELECTROMAGNETISM 162
The Nature of Magnetism ................................................ 162
Magnetic Materials ...................................................... 163
Electromagnetism ....................................................... 164
Magnetic Units .......................................................... 167
BH Magnetization Curve ................................................ 168
Magnetic Circuits ....................................................... 170
Electromagnetic Induction ................................................ 172
International System of Units ............................................. 174
CONTENTS
.................
Chapter 10 DIRECT-CURRENT GENERATORS AND MOTORS 184
Motors and Generators .................................................. 184
Simple DC Generator .................................................... 185
Armature Windings ...................................................... 186
Field Excitation ........................................................ 187
DC Generator Equivalent Circuit .......................................... 188
Generator Voltage Equations and Voltage Regulation ....................... 189
Losses and Efficiency of a DC Machine ................................... 189
Direct-Current Motor .................................................... 191
DC Motor Equivalent Circuit ............................................. 192
Speed of a Motor ....................................................... 193
Motor Types ............................................................ 194
Starting Requirements for Motors ......................................... 1%
.......................
Chapter 11 PRINCIPLES OF ALTERNATING CURRENT 205
Generating an Alternating Voltage ......................................... 205
Angular Measurement ................................................... 205
Sine Wave .............................................................. 206
Alternating Current ...................................................... 207
Frequency and Period ................................................... 208
Phase Relationships ..................................................... 209
Phasors ................................................................ 209
Characteristic Values of Voltage and Current ............................... 211
Resistance in AC Circuits ................................................ 213
Chapter 12 INDUCTANCE. INDUCTIVE REACTANCE. AND INDUCTIVE
.......................................................
CIRCUITS 225
Induction ............................................................... 225
Characteristics of Coils .................................................. 226
Inductive Reactance ..................................................... 227
Inductors in Series or Parallel ............................................ 228
Inductive Circuits ....................................................... 231
Q of a Coil ............................................................. 237
Power in RL Circuits .................................................... 237
Chapter 13 CAPACITANCE. CAPACITIVE REACTANCE. AND CAPACITIVE
.......................................................
CIRCUITS 251
Capacitor ............................................................... 251
Capacitance ............................................................ 252
Types of Capacitors ..................................................... 254
Capacitors in Series and Parallel .......................................... 254
Capacitive Reactance .................................................... 256
Capacitive Circuits ...................................................... 257
Power in RC Circuits .................................................... 262
CONTENTS
.......................................
Chapter 14 SINGLE-PHASE CIRCUITS 275
The General RLC Circuit ................................................ 275
RLC in Series .......................................................... 275
RLC in Parallel ......................................................... 278
RL and RC Branches in Parallel .......................................... 280
Power and Power Factor ................................................. 282
...........
Chapter 15 ALTERNATING-CURRENT GENERATORS AND MOTORS 300
Alternators .............................................................. 300
Paralleling Generators .................................................... 302
Ratings ................................................................. 303
Losses and Efficiency .................................................... 303
Polyphase Induction Motors ............................................... 303
Synchronous Motors ..................................................... 306
Single-Phase Motors ..................................................... 310
................................................
Chapter 16 TRANSFORMERS 322
Ideal Transformer Characteristics ......................................... 322
Transformer Ratings ...................................................... 325
Impedance Ratio ........................................................ 326
Autotransformer ........................................................ 326
Transformer Losses and Efficiency ........................................ 327
No-Load Condition ...................................................... 328
Coil Polarity ............................................................ 329
........................................
Chapter 17 THREE-PHASE SYSTEMS 339
Characteristics of Three-Phase Systems ................................... 339
Three-Phase Transformer Connections .................................... 340
Power in Balanced Three-Phase Loads .................................... 342
Unbalanced Three-Phase Loads ........................................... 346
............................
Chapter 16 SERIES AND PARALLEL RESONANCE 362
Series Resonance ................................................. 362
Q of Series Circuit ................................................ 365
Parallel Resonance ................................................ 366
Q of Parallel Circuit .............................................. 369
Bandwidth and Power of Resonant Circuit .......................... 370
...........................
Chapter 19 WAVEFORMS AND TIME CONSTANTS 384
RL Series Circuit Waveforms ............................................ 384
RL Time Constants ...................................................... 388
RC Series Circuit Waveforms ............................................ 390
RC Time Constants ..................................................... 393
Calculation for Time r ................................................... 394