Electronics & Electrical Principles


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ELECTRONICS & ELECTRICAL PRINCIPLES

Contents

Preface ix

SECTION 1 Basic Electrical and

Electronic Engineering Principles 1

1 Units associated with basic electrical

quantities 3

1.1 SI units 3

1.2 Charge 3

1.3 Force 4

1.4 Work 4

1.5 Power 4

1.6 Electrical potential and e.m.f. 5

1.7 Resistance and conductance 5

1.8 Electrical power and energy 6

1.9 Summary of terms, units and their

symbols 7

2 An introduction to electric circuits 9

2.1 Electrical/electronic system block

diagrams 9

2.2 Standard symbols for electrical

components 10

2.3 Electric current and quantity of

electricity 10

2.4 Potential difference and

resistance 12

2.5 Basic electrical measuring

instruments 12

2.6 Linear and non-linear devices 12

2.7 Ohm’s law 13

2.8 Multiples and sub-multiples 13

2.9 Conductors and insulators 14

2.10 Electrical power and energy 15

2.11 Main effects of electric

current 17

2.12 Fuses 18

3 Resistance variation 20

3.1 Resistance and resistivity 20

3.2 Temperature coefficient of

resistance 22

3.3 Resistor colour coding and ohmic

values 25

4 Chemical effects of electricity 29

4.1 Introduction 29

4.2 Electrolysis 29

4.3 Electroplating 30

4.4 The simple cell 30

4.5 Corrosion 31

4.6 E.m.f. and internal resistance of a

cell 31

4.7 Primary cells 34

4.8 Secondary cells 34

4.9 Cell capacity 35

Assignment 1 38

5 Series and parallel networks 39

5.1 Series circuits 39

5.2 Potential divider 40

5.3 Parallel networks 42

5.4 Current division 45

5.5 Wiring lamps in series and in

parallel 49

6 Capacitors and capacitance 52

6.1 Electrostatic field 52

6.2 Electric field strength 53

6.3 Capacitance 54

6.4 Capacitors 54

6.5 Electric flux density 55

6.6 Permittivity 55

6.7 The parallel plate capacitor 57

6.8 Capacitors connected in parallel

and series 59

6.9 Dielectric strength 62

6.10 Energy stored in capacitors 63

6.11 Practical types of capacitor 64

6.12 Discharging capacitors 66

7 Magnetic circuits 68

7.1 Magnetic fields 68

7.2 Magnetic flux and flux

density 69

7.3 Magnetomotive force and

magnetic field strength 70

7.4 Permeability and B–H curves 70

7.5 Reluctance 73

vi CONTENTS

7.6 Composite series magnetic

circuits 74

7.7 Comparison between electrical

and magnetic quantities 77

7.8 Hysteresis and hysteresis loss 77

Assignment 2 81

8 Electromagnetism 82

8.1 Magnetic field due to an electric

current 82

8.2 Electromagnets 84

8.3 Force on a current-carrying

conductor 85

8.4 Principle of operation of a simple

d.c. motor 89

8.5 Principle of operation of a

moving-coil instrument 89

8.6 Force on a charge 90

9 Electromagnetic induction 93

9.1 Introduction to electromagnetic

induction 93

9.2 Laws of electromagnetic

induction 94

9.3 Inductance 97

9.4 Inductors 98

9.5 Energy stored 99

9.6 Inductance of a coil 99

9.7 Mutual inductance 101

10 Electrical measuring instruments and

measurements 104

10.1 Introduction 104

10.2 Analogue instruments 105

10.3 Moving-iron instrument 105

10.4 The moving-coil rectifier

instrument 105

10.5 Comparison of moving-coil,

moving-iron and moving-coil

rectifier instruments 106

10.6 Shunts and multipliers 106

10.7 Electronic instruments 108

10.8 The ohmmeter 108

10.9 Multimeters 109

10.10 Wattmeters 109

10.11 Instrument ‘loading’ effect 109

10.12 The cathode ray

oscilloscope 111

10.13 Waveform harmonics 114

10.14 Logarithmic ratios 115

10.15 Null method of

measurement 118

10.16 Wheatstone bridge 118

10.17 D.C. potentiometer 119

10.18 A.C. bridges 120

10.19 Q-meter 121

10.20 Measurement errors 122

11 Semiconductor diodes 127

11.1 Types of materials 127

11.2 Silicon and germanium 127

11.3 n-type and p-type materials 128

11.4 The p-n junction 129

11.5 Forward and reverse bias 129

11.6 Semiconductor diodes 130

11.7 Rectification 132

12 Transistors 136

12.1 The bipolar junction

transistor 136

12.2 Transistor action 137

12.3 Transistor symbols 139

12.4 Transistor connections 139

12.5 Transistor characteristics 140

12.6 The transistor as an

amplifier 142

12.7 The load line 144

12.8 Current and voltage gains 145

12.9 Thermal runaway 147

Assignment 3 152

Formulae for basic electrical and electronic

engineering principles 153

SECTION 2 Further Electrical and

Electronic Principles 155

13 D.C. circuit theory 157

13.1 Introduction 157

13.2 Kirchhoff’s laws 157

13.3 The superposition theorem 161

13.4 General d.c. circuit theory 164

13.5 Th´evenin’s theorem 166

13.6 Constant-current source 171

13.7 Norton’s theorem 172

13.8 Th´evenin and Norton equivalent

networks 175

13.9 Maximum power transfer

theorem 179

14 Alternating voltages and currents 183

14.1 Introduction 183

14.2 The a.c. generator 183

14.3 Waveforms 184

14.4 A.C. values 185

CONTENTS vii

14.5 The equation of a sinusoidal

waveform 189

14.6 Combination of waveforms 191

14.7 Rectification 194

Assignment 4 197

15 Single-phase series a.c. circuits 198

15.1 Purely resistive a.c. circuit 198

15.2 Purely inductive a.c. circuit 198

15.3 Purely capacitive a.c. circuit 199

15.4 RL series a.c. circuit 201

15.5 RC series a.c. circuit 204

15.6 RLC series a.c. circuit 206

15.7 Series resonance 209

15.8 Q-factor 210

15.9 Bandwidth and selectivity 212

15.10 Power in a.c. circuits 213

15.11 Power triangle and power

factor 214

16 Single-phase parallel a.c. circuits 219

16.1 Introduction 219

16.2 RL parallel a.c. circuit 219

16.3 RC parallel a.c. circuit 220

16.4 LC parallel a.c. circuit 222

16.5 LRC parallel a.c. circuit 223

16.6 Parallel resonance and

Q-factor 226

16.7 Power factor improvement 230

17 Filter networks 236

17.1 Introduction 236

17.2 Two-port networks and

characteristic impedance 236

17.3 Low-pass filters 237

17.4 High-pass filters 240

17.5 Band-pass filters 244

17.6 Band-stop filters 245

18 D.C. transients 248

18.1 Introduction 248

18.2 Charging a capacitor 248

18.3 Time constant for a CR

circuit 249

18.4 Transient curves for a CR

circuit 250

18.5 Discharging a capacitor 253

18.6 Current growth in an LR

circuit 255

18.7 Time constant for an LR

circuit 256

18.8 Transient curves for an LR

circuit 256

18.9 Current decay in an LR

circuit 257

18.10 Switching inductive circuits 260

18.11 The effects of time constant on a

rectangular waveform 260

19 Operational amplifiers 264

19.1 Introduction to operational

amplifiers 264

19.2 Some op amp parameters 266

19.3 Op amp inverting amplifier 267

19.4 Op amp non-inverting

amplifier 269

19.5 Op amp voltage-follower 270

19.6 Op amp summing amplifier 271

19.7 Op amp voltage comparator 272

19.8 Op amp integrator 272

19.9 Op amp differential

amplifier 274

19.10 Digital to analogue (D/A)

conversion 276

19.11 Analogue to digital (A/D)

conversion 276

Assignment 5 281

Formulae for further electrical and electronic

engineering principles 283

SECTION 3 Electrical Power

Technology 285

20 Three-phase systems 287

20.1 Introduction 287

20.2 Three-phase supply 287

20.3 Star connection 288

20.4 Delta connection 291

20.5 Power in three-phase

systems 293

20.6 Measurement of power in

three-phase systems 295

20.7 Comparison of star and delta

connections 300

20.8 Advantages of three-phase

systems 300

21 Transformers 303

21.1 Introduction 303

21.2 Transformer principle of

operation 304

21.3 Transformer no-load phasor

diagram 306

21.4 E.m.f. equation of

a transformer 308

viii CONTENTS

21.5 Transformer on-load phasor

diagram 310

21.6 Transformer construction 311

21.7 Equivalent circuit of

a transformer 312

21.8 Regulation of a transformer 313

21.9 Transformer losses and

efficiency 314

21.10 Resistance matching 317

21.11 Auto transformers 319

21.12 Isolating transformers 321

21.13 Three-phase transformers 321

21.14 Current transformers 323

21.15 Voltage transformers 324

Assignment 6 327

22 D.C. machines 328

22.1 Introduction 328

22.2 The action of a commutator 329

22.3 D.C. machine construction 329

22.4 Shunt, series and compound

windings 330

22.5 E.m.f. generated in an armature

winding 330

22.6 D.C. generators 332

22.7 Types of d.c. generator and their

characteristics 333

22.8 D.C. machine losses 337

22.9 Efficiency of a d.c.

generator 337

22.10 D.C. motors 338

22.11 Torque of a d.c. motor 339

22.12 Types of d.c. motor and their

characteristics 341

22.13 The efficiency of a d.c.

motor 344

22.14 D.C. motor starter 347

22.15 Speed control of d.c. motors 347

22.16 Motor cooling 350

23 Three-phase induction motors 354

23.1 Introduction 354

23.2 Production of a rotating magnetic

field 354

22.3 Synchronous speed 356

23.4 Construction of a three-phase

induction motor 357

23.5 Principle of operation of a

three-phase induction motor 358

23.6 Slip 358

23.7 Rotor e.m.f. and frequency 359

23.8 Rotor impedance and

current 360

23.9 Rotor copper loss 361

22.10 Induction motor losses and

efficiency 361

23.11 Torque equation for an induction

motor 363

23.12 Induction motor torque-speed

characteristics 366

23.13 Starting methods for induction

motors 367

23.14 Advantages of squirrel-cage

induction motors 367

23.15 Advantages of wound rotor

induction motors 368

23.16 Double cage induction

motor 369

23.17 Uses of three-phase induction

motors 369

Assignment 7 372

Formulae for electrical power

technology 373

Answers to multi-choice questions 375

 

Index 377