E L E C T R I C A L T E C H N O L O G Y ELECTRICAL FUNDAMENTALS Volume I S. P. Bali Former Faculty Member Military College of Electronics and Mechanical Engineering Secunderabad, India Delhi • Chennai Copyright © 2013 Dorling Kindersley (India) Pvt. Ltd. Licensees of Pearson Education in South Asia No part of this eBook may be used or reproduced in any manner whatsoever without the publisher’s prior written consent. This eBook may or may not include all assets that were part of the print version. The publisher reserves the right to remove any material in this eBook at any time. ISBN 9788131785935 eISBN 9789332517677 Head Office: A-8(A), Sector 62, Knowledge Boulevard, 7th Floor, NOIDA 201 309, India Registered Office: 11 Local Shopping Centre, Panchsheel Park, New Delhi 110 017, India Dedicated to My late wife SUKSHAM BALI (10 April 1940 – 07 August 2007) And departing leave behind us FOOTPRINTS on the sands of time Preface A celebrity is a person who works hard all his life to become well known, then wears dark glasses to avoid being recognised. With the rising momentum of development, the scope of text books dealing, in particular, with Electrical Engineering has expanded considerably. An important guiding objective in writing this book is to provide the students with a text book they can read, understand and study by themselves. Intended to serve as a text book for the subject of Electrical Engineering for BE/B.Tech Degree students it will also serve as a text-cum-reference for the students of Diploma Engineering. So also it will be useful to candidates appearing for AMIE, IETE, GATE, UPSC Engineering Services and IAS entrance examination. It will be equally helpful to practicing engineers to understand the theoretical aspects of their professions. Despite the publication of a large number of text books on this fi eld, the students continue to remain perplexed. Keeping this fact in mind, this text book has been developed in a systematic manner, with emphasis on basic concepts. Written in a simple, easy to understand language, reinforced by illustrations which speak of themselves and are easy to understand and supplemented by selected worked examples based on step-by-step solutions the various chapters are interlinked, yet independent. The book can be read in the sequence in which it is written without facing any diffi culty. The following features are intended to serve as learning aids: 1. More than enough worked examples are given in each chapter, wherever applicable to emphasize the practical utility of the results derived. 2. Detailed summary is given at the end of each chapter, as an aid to memory. 3. Multiple choice questions (MCQ) along with their answers are included in each chapter for the self-assessment of the student. 4. The illustrative method of treatment is used, each illustration bringing home a point. 5. Conventional questions are also given at the end of each chapter. Answers to numerical questions are also given. 6. Where possible, mechanical analysis is given. 7. Equivalent circuits are given for a better understanding of the problem. 8. The per unit system is discussed in detail with plenty of worked examples. The book has been designed in two volumes, Volume 1: Electrical Fundamentals and Volume 2: Machines and Meas- urements. Volume 1 comprises Chapters 1 to 30. More stress is given to Electrical Fundamentals which form the founda- tion for further study. Part A of the book on Electrical Fundamentals starts from the requirement of a system of units, how many of them are there, what does it consist of, and which one is prevalent. It further proceeds to explain electrical parameters like resistance R, inductance L and capacitance C as a separate entity and in collaboration as LCR Circuits. The characteristics of these components, their types and construction and control over their extent are explained in detail along with their colour coding and the effect of temperature on their performance. Topics like types of current, potential fall and rise of potential and equipotential surfaces are explained with the help of hydraulic analogy. Networks, series, parallel, and complex and associated terms are explained. Excellent analytical tools that are derived from just three simple scientifi c laws—Ohm’s law and Kirchhoff’s voltage and current laws are explained in detail with the help of worked examples. Circuit elements are defi ned in terms of their circuit equation. This forms the ground for node-pair voltage and mesh current analysis. The idea of fi eld is introduced, the fi eld forming the link between electrical and mechanical systems. Suitability of material for specifi c tasks is explained leading to the topic of losses and effi ciency. The analysis and synthesis of complex waveforms is discussed. First order and second order circuits are discusses leading to Laplace Transform. The natural, forced, and steady state conditions of electrical networks are discussed. Networks a.c. and Networks d.c. are given in separate chapters to distinguish between the two. An in-depth study of network theorems is included and the steps involved in Thevenizing and vi Electrical Technology Nortonizing a circuit are enumerated. Electrochemical energy conversion basics are discussed leading to constant current and constant voltage generators, and conversion from one to the other. After dealing with resonance (LCR Circuits) topics like fi lters and attenuators and transmission lines are covered. Mathematical topics like vectors matrices and determinants, circular and hyperbolic functions are introduced where suitable. After d.c. circuits, single phase a.c. circuits and relevant network theorems are discussed along with plenty of worked out examples; then three phase circuits and delta and star connection and conversion from one to the other followed by step-by-step worked out problems are given. The book also features —a Web-based circuit simulator, specially created to help students practice key circuits. The customized FREE version integrated with the book will enable students to build, analyze and learn the circuits. Besides being used as a practice/pre-lab tool by students, it can also serve as an exciting tool for instructors to teach the circuits. Appendices A to M provide extremely useful information concluding with a brief Glossary of terms have been made available as online resources. Last but not the least I would like to put on record the appreciation of the production and editorial staff in providing me unstained help in completing the project right from the day it was conceived till its completion. Suggestions for improvement of the book will be thankfully acknowledged. S. P. Bali Contents Preface v Summary Multiple Choice Questions (MCQ) Conventional Questions (CQ) PART A: ELECTRICAL FUNDAMENTALS 4. Simple d.c. Circuits 35 1. Systems of Units 3 4.1 Introduction 35 1.1 Introduction 3 4.2 The Basic Circuit 35 1.2 Scientifi c Notation 3 4.3 Resistors 36 1.3 Fundamental and Derived Units 4 4.4 Resistivity (Specifi c Resistance) 36 1.4 Standards and Units 5 4.5 Types of Resistors 40 1.5 Systems of Units 6 4.6 Resistor Tolerance and Wattage 42 1.6 The SI System of Units 6 4.7 Ohm’s Law 43 1.7 Importance of SI System 7 4.8 Lumped Resistance and Distributed 1.8 Defi nitions 8 Resistance 45 Summary 4.9 Leakage Resistance 45 Multiple Choice Questions (MCQ) 4.10 Temperature Coeffi cient of Conventional Questions (CQ) Resistance 45 4.11 Zero Ohm Resistors 48 2. Electrons in Action 12 4.12 Chip Resistors 48 2.1 Introduction 12 4.13 Resistor Networks 48 2.2 Conduction in Solids 12 4.14 Simulated Resistors 50 2.3 Bonding in Atoms 14 4.15 Adjustable Resistors 50 2.4 Energy Bands 16 4.16 Variable Resistors 50 2.5 Electrons in Action 16 4.17 Types of Electric Circuits 51 2.6 Direction of Current Flow 18 4.18 Resistances in Series 51 2.7 Diffusion Current Momentarily 18 4.19 Voltage Division Formula 55 2.8 Drift Velocity 18 4.20 Dominant Resistance 56 2.9 The Nature of Electric Current 19 4.21 Resistors in Parallel 56 2.10 Effects of Electricity 20 4.22 Current Division Formula 58 Summary 4.23 Dominant Resistance 59 Multiple Choice Questions (MCQ) 4.24 Series-Parallel (Complex) Circuits 59 Conventional Questions (CQ) Summary Multiple Choice Questions (MCQ) 3. Electric Circuit 23 Conventional Questions (CQ) 3.1 Introduction 23 5. Networks (d.c.) 69 3.2 Electric Circuit 23 3.3 Current 24 5.1 Introduction 69 3.4 Electromotive Force 25 5.2 Ohm’s Law 69 3.5 Reference Zero 26 5.3 Kirchhoff’s Laws 71 3.6 Safety Precautions While Handling 5.4 Voltage Drop and Polarity 72 Electric Circuits 26 5.5 Equipotential Points 73 3.7 Insulators 27 5.6 The Bridge Network 73 3.8 Semiconductors 28 5.7 Networks 78 3.9 Conductors 30 5.8 Superposition Theorem 78 viii Electrical Technology 5.9 Voltage and Current Sources 80 7.15 The Electrolyte 148 5.10 Dependent Voltage Sources 85 7.16 Capacity of Cells 148 5.11 Millman’s Theorem 86 7.17 Internal Resistance of 5.12 Thevenin’s Theorem 87 Secondary Cells 149 5.13 Thevenizing a Circuit 88 7.18 Makeup of Cells 149 5.14 Norton’s Theorem 90 7.19 Charging and Discharging of 5.15 Nortonizing a Circuit 90 Lead-Acid Secondary Batteries 149 5.16 Maximum Power Transfer Theorem 91 7.20 Constant Current Charging 150 5.17 Effi ciency 93 7.21 Constant Voltage Charging 151 5.18 Δ Y Transformation 94 7.22 Effi ciencies of a Cell 151 5.19 Balanced Networks 97 7.23 Faults 151 5.20 Network Reduction 97 7.24 Alkaline Cells 151 5.21 Mesh Currents 97 7.25 Nife Nickel Cadmium Alkaline Cell 152 5.22 Node-Voltages 98 7.26 Mercury Cell 152 Summary 7.27 Silver-Oxide Cell 153 Multiple Choice Questions (MCQ) 7.28 Grouping of Cells 153 Conventional Questions (CQ) 7.29 Grouping Cells for Maximum Current 154 6. Mesh-Current and Summary Node-Voltage Analysis 113 Multiple Choice Questions (MCQ) Conventional Questions (CQ) 6.1 Introduction 113 6.2 Matrices and Determinants 113 8. Electromagnetism 162 6.3 Network Analysis by Mesh Current 118 6.4 Network Analysis by Node-Pair 8.1 Introduction 162 Voltages 121 8.2 Attraction and Repulsion 163 6.5 The Resistance Matrix 122 8.3 The Inverse Square Law 163 6.6 The Conductance Matrix 123 8.4 Lines of Force 164 6.7 The Super Mesh 124 8.5 Magnetic Flux 165 6.8 The Super Node 126 8.6 Permeability 165 6.9 Nodal Analysis Vs Mesh Analysis—A 8.7 Permeability (B–H) Curves 166 Comparison 127 8.8 The Domain Theory of Magnetism 166 Summary 8.9 Electromagnetism 170 Multiple Choice Questions (MCQ) 8.10 Direction of Magnetic Field 171 Conventional Questions (CQ) 8.11 Magnetizing Force of Electromagnetic Fields 171 7. Electrochemical Action 135 8.12 Indicating the Direction of 7.1 Introduction 135 Current Flow 172 7.2 Primary Cells 136 8.13 Rule of Direction 172 7.3 Electrolysis 136 8.14 Electrodynamic Forces 173 7.4 Faraday’s Laws 137 8.15 Forces between Magnetic Poles 174 7.5 Simple Voltaic Cell 139 8.16 Magnetic Moment 174 7.6 e.m.f. of a Cell 140 8.17 Flux Density of a Solenoid 175 7.7 Local Action 140 8.18 Magnetic Circuit 175 7.8 Polarization 141 8.19 Magnetic Induction 178 7.9 Internal Resistance 141 8.20 Magnetic Shields 180 7.10 Characteristics of a Good Cell 144 8.21 Reluctance 180 7.11 The Leclanche Cell 144 8.22 Series Magnetic Circuits 181 7.12 The Dry Cell 145 8.23 Parallel Magnetic Circuit 183 7.13 Secondary Batteries/Cells 146 8.24 Electromagnets 184 7.14 Elements of Secondary Cells 147 8.25 Electromagnetic Relays 186 Contents ix Summary 12. Electrostatics 235 Multiple Choice Questions (MCQ) 12.1 Introduction 235 Conventional Questions (CQ) 12.2 Electrifi cation by Friction 235 9. Inductors 190 12.3 Application of Electron Theory 236 12.4 Coulomb’s Law 237 9.1 Introduction 190 12.5 Permittivity 237 9.2 Inductance 191 12.6 Electrostatic Induction 238 9.3 Factors Determining Inductance 192 12.7 The Gold-Leaf Electroscope 239 9.4 Energy Stored in the Magnetic Field of an 12.8 Electric Fields 240 Inductor 194 12.9 Electric Flux 241 9.5 Losses in Inductors 194 12.10 Potential 241 9.6 Toroids 195 12.11 Equipotential Lines 241 9.7 Inductor Types 196 12.12 Gauss’s Law 242 9.8 Time-Constant 196 12.13 Dielectric Strength 244 9.9 Graphical Derivation of the Transient 12.14 The Electric Field Due to a Line of Characteristics of an R-L Circuit 200 Charge 244 9.10 Universal Time Constant 203 12.15 The Electric Field Due to a Charged 9.11 Inductors in Series and Parallel 205 Disk 245 9.12 Transient Behaviour 207 Summary Summary Multiple Choice Questions (MCQ) Multiple Choice Questions (MCQ) Conventional Questions (CQ) Conventional Questions (CQ) 13. Capacitors and d.c. Transients 249 10. Hysteresis 211 13.1 Introduction 249 10.1 Introduction 211 13.2 Capacitance 249 10.2 The B-H Curve 211 13.3 Capacitor Action 250 10.3 Hysteresis Loop 212 13.4 Permittivity 251 10.4 Hysteresis Loss 212 13.5 Factors Determining Capacitance 252 10.5 Determination of B-H Curve 213 13.6 Energy Stored in the Electric Field 10.6 Determination of Hysteresis Loop 215 between the Capacitor Plates 254 10.7 Hysteresis Loss 216 13.7 Power Factor (Capacitors) 254 10.8 Eddy Currents 219 13.8 Types of Capacitors 255 10.9 Eddy Current Losses 220 13.9 Capacitor Colourcode 258 10.10 Separation of Hysteresis and Eddy 13.10 Time Constant 262 Current Losses 221 Summary 13.11 Graphical Derivation of the Transient Multiple Choice Questions (MCQ) Characteristics of an R-C Circuit 263 Conventional Questions (CQ) 13.12 Universal Time Constant 266 13.13 Connecting Capacitors in Series 269 11. Magnetic Materials 226 13.14 Connecting Capacitors in Parallel 270 Summary 11.1 Introduction 226 Multiple Choice Questions (MCQ) 11.2 Magnetic Materials 226 Conventional Questions (CQ) 11.3 Non-Magnetic Alloys 228 11.4 Ferrites 228 14. Dielectric Materials 277 11.5 Magnetic Materials with Rectangular Hysteresis Loops 229 14.1 Introduction 277 11.6 Grain-Oriented Magnetic Material 230 14.2 Dielectric Materials 277 11.7 Permanent Magnets 230 14.3 Permittivity (Dielectric Constant) 277 Summary 14.4 Power Factor 278 Multiple Choice Questions (MCQ) 14.5 Insulation Resistance (or Insulance) 278 Conventional Questions (CQ) 14.6 Dielectric Absorption 278