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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 R–L series a.c. circuit 201
15.5 R–C series a.c. circuit 204
15.6 R–L–C 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 R–L parallel a.c. circuit 219
16.3 R–C parallel a.c. circuit 220
16.4 L–C parallel a.c. circuit 222
16.5 LR–C 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 C–R
circuit 249
18.4 Transient curves for a C–R
circuit 250
18.5 Discharging a capacitor 253
18.6 Current growth in an L–R
circuit 255
18.7 Time constant for an L–R
circuit 256
18.8 Transient curves for an L–R
circuit 256
18.9 Current decay in an L–R
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