1.6 Special Features of This Book 112.1 Charge, Current, and Kirchhoff’s Current Law 16 2.2 Voltage and Kirchhoff’s Voltage Law 21 2.3 Ideal Voltage and Current Sources 23 Ideal Voltage
Trang 11.6 Special Features of This Book 11
2.1 Charge, Current, and Kirchhoff’s
Current Law 16
2.2 Voltage and Kirchhoff’s Voltage Law 21
2.3 Ideal Voltage and Current Sources 23
Ideal Voltage Sources 24
Ideal Current Sources 25
Dependent (Controlled) Sources 25
2.4 Electric Power and Sign Convention 26
2.5 Circuit Elements and Their
i-v Characteristics 29
2.6 Resistance and Ohm’s Law 30
Open and Short Circuits 38
Series Resistors and the Voltage
3.1 The Node Voltage Method 72Nodal Analysis with Voltage Source 77
3.2 The Mesh Current Method 78Mesh Analysis with Current Sources 82
3.3 Nodal and Mesh Analysis with Controlled Sources 84
Remarks on Node Voltage and Mesh Current Methods 86
3.4 The Principle of Superposition 86
3.5 One-Port Networks and Equivalent Circuits 89
Thévenin and Norton Equivalent Circuits 90Determination of Norton or Thévenin
Equivalent Resistance 91Computing the Thévenin Voltage 95Computing the Norton Current 99Source Transformations 101Experimental Determination of Théveninand Norton Equivalents 104
3.6 Maximum Power Transfer 107
3.7 Nonlinear Circuit Elements 110Description of Nonlinear Elements 110Graphical (Load-Line) Analysis of NonlinearCircuits 111
4.1 Energy-Storage (Dynamic) Circuit Elements 126
The Ideal Capacitor 126Energy Storage in Capacitors 130The Ideal Inductor 133
Energy Storage in Inductors 137
4.2 Time-Dependent Signal Sources 141Why Sinusoids? 141
Average and RMS Values 142
Trang 24.3 Solution of Circuits Containing Dynamic
Natural Response of First-Order Circuits 187
Forced and Complete Response of First-Order
Circuits 191
Continuity of Capacitor Voltages and Inductor
Circuits 192
Complete Solution of First-Order Circuits 194
5.4 Transient Response of First-Order
Circuits 203
Deriving the Differential Equations
for Second-Order Circuits 204
Natural Response of Second-Order
Decibel (db) or Bode Plots 257
6.3 Complex Frequency and the Laplace
Transform 260
The Laplace Transform 263Transfer Functions, Poles, and Zeros 267
7.1 Power in AC Circuits 282Instantaneous and Average Power 282
AC Power Notation 284Power Factor 288
7.2 Complex Power 289Power Factor, Revisited 294
7.3 Transformers 308The Ideal Transformer 309Impedance Reflection and Power Transfer 311
7.4 Three-Phase Power 315Balanced Wye Loads 318Balanced Delta Loads 319
7.5 Residential Wiring; Grounding
and Safety 322
7.6 Generation and Distribution of AC Power 325
8.1 Electrical Conduction in Semiconductor
8.4 Practical Diode Circuits 360The Full-Wave Rectifier 360The Bridge Rectifier 362
DC Power Supplies, Zener Diodes, and Voltage Regulation 364Signal-Processing Applications 370Photodiodes 377
9.1 Transistors as Amplifiers and Switches 392
9.2 The Bipolar Junction Transistor (BJT) 394Determining the Operating Region
of a BJT 397Selecting an Operating Point for a BJT 399
Chapter 5 Transient Analysis 181
Chapter 6 Frequency Respose
and System Concepts 231
Chapter 7 AC Power 281
Chapter 8 Semiconductors and Diodes 337
Chapter 9 Transistor Fundamentals 391
Trang 3Junction Field-Effect Transistors 424
Depletion MOSFET and JFET
Other BJT Amplifier Circuits 457
10.3 FET Small-Signal Amplifiers 457
The MOSFET Common-Source
11.5 Rectifiers and Controlled Rectifiers
(AC-DC Converters) 508Three-Phase Rectifiers 511Thyristors and Controlled Rectifiers 512
11.6 Electric Motor Drives 518
Choppers (DC-DC Converters) 518Inverters (DC-AC Converters) 523
12.1 Amplifiers 532
Ideal Amplifier Characteristics 532
12.2 The Operational Amplifier 533
The Open-Loop Model 534The Operational Amplifier
in the Closed-Loop Mode 535
12.3 Active Filters 553
12.4 Integrator and Differentiator Circuits 559
The Ideal Differentiator 562
12.5 Analog Computers 562
Scaling in Analog Computers 564
12.6 Physical Limitations of Op-Amps 569
Voltage Supply Limits 569Frequency Response Limits 571Input Offset Voltage 574Input Bias Currents 575Output Offset Adjustment 576Slew Rate Limit 577
Short-Circuit Output Current 579Common-Mode Rejection Ratio 580
13.1 Analog and Digital Signals 600
13.2 The Binary Number System 602
Addition and Subtraction 602Multiplication and Division 603Conversion from Decimal to Binary 603Complements and Negative Numbers 604The Hexadecimal System 606
Binary Codes 606
13.3 Boolean Algebra 610
AND and OR Gates 610NAND and NOR Gates 617The XOR (Exlusive OR) Gate 619
Chapter 10 Transistor Amplifiers
and Switches 437
Chapter 11 Power Electronics 495
Chapter 12 Operational Amplifiers 531
Chapter 13 Digital Logic Circuits 599
Trang 413.4 Karnaugh Maps and Logic Design 620
Sum-of-Products Realizations 623
Product-of-Sums Realizations 627
Don’t Care Conditions 631
13.5 Combinational Logic Modules 634
Multiplexers 634
Read-Only Memory (ROM) 635
Decoders and Read and Write Memory 638
14.1 Sequential Logic Modules 648
Latches and Flip-Flops 648
Noise Sources and Coupling Mechanisms 697
Noise Reduction 698
15.3 Signal Conditioning 699Instrumentation Amplifiers 699Active Filters 704
15.4 Analog-to-Digital and Digital-to-Analog
Conversion 713Digital-to-Analog Converters 714Analog-to-Digital Converters 718Data Acquisition Systems 723
15.5 Comparator and Timing Circuits 727The Op-Amp Comparator 728The Schmitt Trigger 731The Op-Amp Astable Multivibrator 735The Op-Amp Monostable Multivibrator (One-Shot) 737
Timer ICs: The NE555 740
15.6 Other Instrumentation Integrated Circuits
Amplifiers 742DACs and ADCs 743Frequency-to-Voltage, Voltage-to-Frequency Converters and Phase-Locked Loops 743Other Sensor and Signal Conditioning Circuits 743
15.7 Data Transmission in Digital
Instruments 748The IEEE 488 Bus 749The RS-232 Standard 753
16.1 Electricity and Magnetism 768The Magnetic Field and Faraday’s Law 768Self- and Mutual Inductance 771
Chapter 14 Digital Systems 647
Trang 517.1 Rotating Electric Machines 828
Basic Classification of Electric Machines 828
Performance Characteristics of Electric
Rotating Magnetic Fields 862
17.6 The Alternator (Synchronous
Generator) 864
17.7 The Synchronous Motor 866
17.8 The Induction Motor 870
Performance of Induction Motors 877
AC Motor Speed and Torque Control 879
Adjustable-Frequency Drives 880
18.1 Brushless DC Motors 890
18.2 Stepping Motors 897
18.3 Switched Reluctance Motors 905
Operating Principles of SR Machine 906
18.4 Single-Phase AC Motors 908
The Universal Motor 909
Single-Phase Induction Motors 912
Classification of Single-Phase Induction
Motors 917
Summary of Single-Phase Motor
Characteristics 922
18.5 Motor Selection and Application 923
Motor Performance Calculations 923
Classification of Communication Systems
19.2 Signals and Their SpectraSignal Spectra
Periodic Signals: Fourier SeriesNon-Periodic Signals: The Fourier TransformBandwidth
19.3 Amplitude Modulation and DemodulationBasic Principle of AM
AM Demodulaton: Integrated Circuit ReceiversComment on AM Applications
19.4 Frequency Modulation and DemodulationBasic Principle of FM
Chapter 17 Introduction
to Electric Machines 827
Chapter 19 Introduction
to Communication Systems
Appendix A Linear Algebra and Complex Numbers 933 Appendix B Fundamentals
of Engineering (FE) Examination 941 Appendix C Answers
to Selected Problems 955 Index 961
Chapter 18 Special-Purpose
Electric Machines 889
Trang 61
Introduction to Electrical
Engineering
he aim of this chapter is to introduce electrical engineering The chapter is
organized to provide the newcomer with a view of the different specialties
making up electrical engineering and to place the intent and organization
of the book into perspective Perhaps the first question that surfaces in the
mind of the student approaching the subject is, Why electrical engineering? Since
this book is directed at a readership having a mix of engineering backgrounds
(including electrical engineering), the question is well justified and deserves some
discussion The chapter begins by defining the various branches of electrical
engi-neering, showing some of the interactions among them, and illustrating by means
of a practical example how electrical engineering is intimately connected to many
other engineering disciplines In the second section, mechatronic systems
engi-neering is introduced, with an explanation of how this book can lay the foundation
for interdisciplinary mechatronic product design This design approach is
illus-trated by an example The next section introduces the Engineer-in-Training (EIT)
national examination A brief historical perspective is also provided, to outline the
growth and development of this relatively young engineering specialty Next, the
fundamental physical quantities and the system of units are defined, to set the stage
for the chapters that follow Finally, the organization of the book is discussed, to
give the student, as well as the teacher, a sense of continuity in the development
of the different subjects covered in Chapters 2 through 18
Trang 71.1 ELECTRICAL ENGINEERING
The typical curriculum of an undergraduate electrical engineering student includesthe subjects listed in Table 1.1 Although the distinction between some of thesesubjects is not always clear-cut, the table is sufficiently representative to serve ourpurposes Figure 1.1 illustrates a possible interconnection between the disciplines
of Table 1.1 The aim of this book is to introduce the non-electrical engineeringstudent to those aspects of electrical engineering that are likely to be most relevant
to his or her professional career Virtually all of the topics of Table 1.1 will betouched on in the book, with varying degrees of emphasis The following exampleillustrates the pervasive presence of electrical, electronic, and electromechanicaldevices and systems in a very common application: the automobile As you readthrough the example, it will be instructive to refer to Figure 1.1 and Table 1.1
Electric power systems
Digital logic circuits
Engineering applications
Mathematical foundations
Electric machinery
Analog electronics
Digital electronics
Computer systems
Network theory
Logic theory
System theory
Physical foundations
magnetics
Electro-Solid-state physics
Optics
Control systems
Communication systems
Instrumentation systems
Figure 1.1 Electrical engineering disciplines
EXAMPLE 1.1 Electrical Systems in a Passenger Automobile
A familiar example illustrates how the seemingly disparate specialties of electricalengineering actually interact to permit the operation of a very familiar engineeringsystem: the automobile Figure 1.2 presents a view of electrical engineering systems in a
Trang 8Antilock brake Traction Suspension Power steering 4-wheel steer Tire pressure
Analog dash Digital dash Navigation
Cellular phone CD/DAT AM/FM radio Digital radio
TV sound
Body electronics
Vehicle control
Power train
Instrumentation Entertainment
Figure 1.2 Electrical engineering systems in the automobile
modern automobile Even in older vehicles, the electrical system—in effect, an electric
circuit—plays a very important part in the overall operation An inductor coil generates a
sufficiently high voltage to allow a spark to form across the spark plug gap, and to ignite
the air and fuel mixture; the coil is supplied by a DC voltage provided by a lead-acid
battery In addition to providing the energy for the ignition circuits, the battery also
supplies power to many other electrical components, the most obvious of which are the
lights, the windshield wipers, and the radio Electric power is carried from the battery to
all of these components by means of a wire harness, which constitutes a rather elaborate
electrical circuit In recent years, the conventional electrical ignition system has been
supplanted by electronic ignition; that is, solid-state electronic devices called transistors
have replaced the traditional breaker points The advantage of transistorized ignition
systems over the conventional mechanical ones is their greater reliability, ease of control,
and life span (mechanical breaker points are subject to wear)
Other electrical engineering disciplines are fairly obvious in the automobile The
on-board radio receives electromagnetic waves by means of the antenna, and decodes the
communication signals to reproduce sounds and speech of remote origin; other common
communication systems that exploit electromagnetics are CB radios and the ever more
common cellular phones But this is not all! The battery is, in effect, a self-contained
12-VDC electric power system, providing the energy for all of the aforementioned
functions In order for the battery to have a useful lifetime, a charging system, composed
of an alternator and of power electronic devices, is present in every automobile The
alternator is an electric machine, as are the motors that drive the power mirrors, power
windows, power seats, and other convenience features found in luxury cars Incidentally,
the loudspeakers are also electric machines!
Trang 9The list does not end here, though In fact, some of the more interesting applications
of electrical engineering to the automobile have not been discussed yet Consider
computer systems You are certainly aware that in the last two decades, environmental
concerns related to exhaust emissions from automobiles have led to the introduction of
sophisticated engine emission control systems The heart of such control systems is a type
of computer called a microprocessor The microprocessor receives signals from devices (called sensors) that measure relevant variables—such as the engine speed, the
concentration of oxygen in the exhaust gases, the position of the throttle valve (i.e., thedriver’s demand for engine power), and the amount of air aspirated by the engine—andsubsequently computes the optimal amount of fuel and the correct timing of the spark toresult in the cleanest combustion possible under the circumstances The measurement of
the aforementioned variables falls under the heading of instrumentation, and the interconnection between the sensors and the microprocessor is usually made up of digital
circuits Finally, as the presence of computers on board becomes more pervasive—in
areas such as antilock braking, electronically controlled suspensions, four-wheel steeringsystems, and electronic cruise control—communications among the various on-boardcomputers will have to occur at faster and faster rates Some day in the not-so-distant
future, these communications may occur over a fiber optic network, and electro-optics
will replace the conventional wire harness It should be noted that electro-optics is alreadypresent in some of the more advanced displays that are part of an automotive
auto-adopted in Europe, mechatronic design has surfaced as a new philosophy of
de-sign, based on the integration of existing disciplines—primarily mechanical, andelectrical, electronic, and software engineering.1
A very important issue, often neglected in a strictly disciplinary approach
to engineering education, is the integrated aspect of engineering practice, which
is unavoidable in the design and analysis of large scale and/or complex systems.One aim of this book is to give engineering students of different backgroundsexposure to the integration of electrical, electronic, and software engineering intotheir domain This is accomplished by making use of modern computer-aidedtools and by providing relevant examples and references Section 1.6 describeshow some of these goals are accomplished
1 D A Bradley, D Dawson, N C Burd, A J Loader, 1991, “Mechatronics, Electronics in Products
and Processes,” Chapman and Hall, London See also ASME/IEEE Transactions on Mechatronics,
Vol 1, No 1, 1996.
Trang 10Example 1.2 illustrates some of the thinking behind the mechatronic system
design philosophy through a practical example drawn from the design experience
of undergraduate students at a number of U.S universities
EXAMPLE 1.2 Mechatronic Systems—Design of a Formula
Lightning Electric Race Car
The Formula Lightning electric race car competition is an interuniversity2competition
project that has been active since 1994 This project involves the design, analysis, and
testing of an electric open-wheel race car A photo and the generic layout of the car are
shown in Figures 1.3 and 1.4 The student-designed propulsion and energy storage
systems have been tested in interuniversity competitions since 1994 Projects have
included vehicle dynamics and race track simulation, motor and battery pack selection,
battery pack and loading system design, and transmission and driveline design This is an
ongoing competition, and new projects are defined in advance of each race season The
objective of this competitive series is to demonstrate advancement in electric drive
technology for propulsion applications using motorsports as a means of extending existing
technology to its performance limit This example describes some of the development that
has taken place at the Ohio State University The description given below is representative
of work done at all of the participating universities
Figure 1.3 The Ohio State University Smokin’
Buckeye
+ – + – + – + – + – + – + – +
24 V–
+ – + – + – + – + – + – + – +
24 V–
DC-AC converter (electric drive)
AC motor
Instrumentation panel
Battery pack
Gearbox Differential
Figure 1.4 Block diagram of electric race car
Design Constraints:
The Formula Lightning series is based on a specification chassis; thus, extensive
modifications to the frame, suspension, brakes, and body are not permitted The focus of
the competition is therefore to optimize the performance of the spec vehicle by selecting a
2 Universities that have participated in this competition are Arizona State University, Bowling Green
State University, Case Western Reserve University, Kettering University, Georgia Institute of
Technology, Indiana University—Purdue University at Indianapolis, Northern Arizona University,
Notre Dame University, Ohio State University, Ohio University, Rennselaer Polytechnic Institute,
University of Oklahoma, and Wright State University.
Trang 11suitable combination of drivetrain and energy storage components In addition, since thevehicle is intended to compete in a race series, issues such as energy management, quickand efficient pit stops for battery pack replacement, and the ability to adapt systemperformance to varying race conditions and different race tracks are also important designconstraints.
Design Solutions:3
Teams of undergraduate aerospace, electrical, industrial, and mechanical engineeringstudents participate in the design of the all-electric Formula Lightning drivetrain through aspecial design course, made available especially for student design competitions
In a representative course at Ohio State, the student team was divided into fourgroups: battery system selection, motor and controller selection, transmission anddriveline design, and instrumentation and vehicle dynamics Each of these groups wascharged with the responsibility of determining the technology that would be best suited tomatching the requirements of the competition and result in a highly competitive vehicle
Figure 1.5 illustrates the interdisciplinary mechatronics team approach; it is apparent
that, to arrive at an optimal solution, an iterative process had to be followed and that thevarious iterations required significant interaction between different teams
To begin the process, a gross vehicle weight was assumed and energy storagelimitations were ignored in a dynamic computer simulation of the vehicle on a simulatedroad course (the Cleveland Grand Prix Burke Lakefront Airport racetrack, site of the firstrace in the series) The simulation employed a realistic model of the vehicle and tiredynamics, but a simple model of an electric drive—energy storage limitations would beconsidered later
Vehicle-track dynamic simulation
Vehicle weight and weight distribution
Motor Torque-speed curves
Lap time
Energy consumption
Energy Gear and final
drive ratios
Motor selection
Transmission selection
Battery selection
Figure 1.5 Iterative design process for electric race car drivetrain
The simulation was exercised under various scenarios to determine the limitperformance of the vehicle and the choice of a proper drivetrain design The first round ofsimulations led to the conclusion that a multispeed gearbox would be a necessity for
3 K Grider, G Rizzoni, “Design of the Ohio State University electric race car,” SAE Technical Paper
in Proceedings, 1996 SAE Motorsports Conference and Exposition, Dearborn, MI, Dec.10–12,
1996.
Trang 12competitive performance on a road course, and also showed the need for a very high
performance AC drive as the propulsion system The motor and controller are depicted in
Figure 1.6
Figure 1.6 Motor and controller
Once the electric drive had been selected, the results of battery tests performed by the
battery team were evaluated to determine the proper battery technology, and the resulting
geometry and weight distribution of the battery packs With the preferred battery
technology identified (see Figure 1.7), energy criteria was included in the simulation, and
lap times and energy consumption were predicted Finally, appropriate instrumentation
was designed to permit monitoring of the most important functions in the vehicle (e.g.,
battery voltage and current, motor temperature, vehicle and motor speed) Figure 1.8
depicts the vehicle dashboard Table 1.2 gives the specifications for the vehicle
Figure 1.7 Open side pod with battery pack and single battery
Figure 1.8 Dashboard
Table 1.2 Smokin’ Buckeye specifications
Drive system:
Vector controlled AC propulsion model 150
Motor type: three-phase induction, 150 kW
Weight: motor 100 lb, controller 75 lb
Motor dimensions: 12-in diameter, 15-in length
Transmission/clutch:
Webster four-speed supplied by Taylor Race Engineering
Tilton metallic clutch
Battery system:
Total voltage: 372 V (nominal)
Total weight: 1440 lb
Number of batteries: 31
Battery: Optima spiral-wound lead-acid gel-cell battery
Configuration: 16 battery packs, 12 or 24 V each
Instrumentation:
Ohio Semitronics model EV1 electric vehicle monitor
Stack model SR 800 Data Acquisition
Shocks: Penske racing coil-over shocks
Brakes: Wilwood Dynalite II
Trang 13Altogether approximately 30 students from different engineering disciplinesparticipated in the initial design process They received credit for their effort eitherthrough the course—ME 580.04, Analysis, Design, Testing and Fabrication of AlternativeVehicles—or through a senior design project As noted, interaction among teams andamong students from different disciplines was an integral part of the design process.
Comments: The example illustrates the importance of interdisciplinary thinking in thedesign of mechatronics systems The aim of this book is to provide students in differentengineering disciplines with the foundations of electrical/electronic engineering that arenecessary to effectively participate in interdisciplinary engineering design projects Thenext 17 chapters will present the foundations and vocabulary of electrical engineering
Fundamentals of Engineering (FE) Examination This is an eight-hour exam that
covers general engineering undergraduate education The third requirement istwo to four years of engineering experience after passing the FE exam Finally,
the fourth requirement is successful completion of the Principles and Practice of
Engineering or Professional Engineer (PE) Examination.
The FE exam is a two-part national examination given twice a year (in Apriland October) The exam is divided into two 4-hour sessions The morning sessionconsists of 140 multiple choice questions (five possible answers are given); theafternoon session consists of 70 questions The exam is prepared by the StateBoard of Engineers for each state
One of the aims of this book is to assist you in preparing for one part ofthe FE exam, entitled Electrical Circuits This part of the examination consists of
a total of 18 questions in the morning session and 10 questions in the afternoonsession The examination topics for the electrical circuits part are the following:
DC Circuits
AC CircuitsThree-Phase CircuitsCapacitance and InductanceTransients
Diode ApplicationsOperational Amplifiers (Ideal)Electric and Magnetic FieldsElectric Machinery
Appendix B contains a complete review of the Electrical Circuits portion
of the FE examination In Appendix B you will find a detailed listing of the
Trang 14topics covered in the examination, with references to the relevant material in the
book The appendix also contains a collection of sample problems similar to those
found in the examination, with answers These sample problems are arranged in
two sections: The first includes worked examples with a full explanation of the
solution; the second consists of a sample exam with answers supplied separately
This material is based on the author’s experience in teaching the FE Electrical
Circuits review course for mechanical engineering seniors at Ohio State University
over several years
ENGINEERING
The historical evolution of electrical engineering can be attributed, in part, to
the work and discoveries of the people in the following list You will find these
scientists, mathematicians, and physicists referenced throughout the text
William Gilbert (1540–1603), English physician, founder of magnetic
science, published De Magnete, a treatise on magnetism, in 1600.
Charles A Coulomb (1736–1806), French engineer and physicist,
published the laws of electrostatics in seven memoirs to the French
Academy of Science between 1785 and 1791 His name is associated with
the unit of charge
James Watt (1736–1819), English inventor, developed the steam engine.
His name is used to represent the unit of power
Alessandro Volta (1745–1827), Italian physicist, discovered the electric
pile The unit of electric potential and the alternate name of this quantity
(voltage) are named after him
Hans Christian Oersted (1777–1851), Danish physicist, discovered the
connection between electricity and magnetism in 1820 The unit of
magnetic field strength is named after him
Andr´e Marie Amp`ere (1775–1836), French mathematician, chemist, and
physicist, experimentally quantified the relationship between electric
current and the magnetic field His works were summarized in a treatise
published in 1827 The unit of electric current is named after him
Georg Simon Ohm (1789–1854), German mathematician, investigated the
relationship between voltage and current and quantified the phenomenon of
resistance His first results were published in 1827 His name is used to
represent the unit of resistance
Michael Faraday (1791–1867), English experimenter, demonstrated
electromagnetic induction in 1831 His electrical transformer and
electromagnetic generator marked the beginning of the age of electric
power His name is associated with the unit of capacitance
Joseph Henry (1797–1878), American physicist, discovered
self-induction around 1831, and his name has been designated to represent
the unit of inductance He had also recognized the essential structure of the
telegraph, which was later perfected by Samuel F B Morse
Carl Friedrich Gauss (1777–1855), German mathematician, and
Wilhelm Eduard Weber (1804–1891), German physicist, published a
Trang 15treatise in 1833 describing the measurement of the earth’s magnetic field.The gauss is a unit of magnetic field strength, while the weber is a unit ofmagnetic flux.
James Clerk Maxwell (1831–1879), Scottish physicist, discovered the
electromagnetic theory of light and the laws of electrodynamics Themodern theory of electromagnetics is entirely founded upon Maxwell’sequations
Ernst Werner Siemens (1816–1892) and Wilhelm Siemens (1823–1883),
German inventors and engineers, contributed to the invention anddevelopment of electric machines, as well as to perfecting electricalscience The modern unit of conductance is named after them
Heinrich Rudolph Hertz (1857–1894), German scientist and
experimenter, discovered the nature of electromagnetic waves andpublished his findings in 1888 His name is associated with the unit offrequency
Nikola Tesla (1856–1943), Croatian inventor, emigrated to the United
States in 1884 He invented polyphase electric power systems and theinduction motor and pioneered modern AC electric power systems Hisname is used to represent the unit of magnetic flux density
This book employs the International System of Units (also called SI, from the
French Syst`eme International des Unit´es) SI units are commonly adhered to by
virtually all engineering professional societies This section summarizes SI unitsand will serve as a useful reference in reading the book
SI units are based on six fundamental quantities, listed in Table 1.3 Allother units may be derived in terms of the fundamental units of Table 1.3 Since,
in practice, one often needs to describe quantities that occur in large multiples orsmall fractions of a unit, standard prefixes are used to denote powers of 10 of SI(and derived) units These prefixes are listed in Table 1.4 Note that, in general,engineering units are expressed in powers of 10 that are multiples of 3
Table 1.4 Standard prefixes
Prefix Symbol Power
atto a 10 −18 femto f 10 −15 pico p 10 −12 nano n 10 −9 micro µ 10 −6 milli m 10 −3 centi c 10 −2 deci d 10 −1