preface to the second edition -...

Preface to the Second Edition xiii

Preface to the Second Edition

The main purpose of bringing out the second edition of this book was to make it more suitable for students of Electronics and Communication Engineering at the undergraduate level. To this end, certain sections have been added in the second edition including sections on Circular Waveguide, Dielectric Slab Waveguide, and Optical-Fibre Waveguide in Chapter 9; and sections on Circular Loop Antenna, Parabolic Reflector Antenna, and Electromagnetic Interference in Chapter 10. Considering their importance and acceptance, all the materials of the first edition are included in the second edition, albeit with the following alterations/rearrangements: ❑ Partial Derivatives of Unit Vectors in Spherical and Cylindrical Coordinates provided in Section 1.8

of the first edition are shifted to Appendix A. ❑ Internal Impedance of Round Conductors, provided in Appendix B of the first edition, is shifted to

Section 6.21 after revision. ❑ Section sub-headings have been numbered for easy reference.❑ The second edition has more Examples, Multiple-Choice or Objective Questions, Questions, and

Problems.❑ Problems at the end of the chapters have been arranged section-wise.

What Makes this Book Unique?

Some of the major highlights of this book are listed below:❑ Dedicated solutions to boundary-value problems for both Electrostatics and Magnetostatics❑ Covers important topics like Circular Waveguide, Dielectric Slab Waveguide, Optical Fibre

Waveguide, Circular Antenna, and Parabolic Reflector Antenna❑ List of Important Formulae at the end of each chapter❑ Important Notes and Keywords highlighted within the text

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Principles of Electromagneticsxiv Preface to the Second Editionxiv

❑ Answers to select theory questions at the end of each chapter❑ Answers to unsolved numerical problems are given at the end of the book❑ Excellent pedagogy

● Illustrations: 305● Solved Examples: 297● Theory Questions: 302● Multiple-Choice Questions: 187● Problems: 429

Online Learning Center

The Online Learning Center can be accessed at http://www.mhhe.com/mahapatra/pe2 and contains the Instructor’s Manual and PowerPoint Lecture Slides for instructors.

Acknowledgements

We would like to extend our thanks to Prof. Kalyan Kumar Bandyopadhyay and Prof. Ajay Chakrabarty of the Department of E&ECE, IIT Kharagpur and also the following reviewers who gave us valuable suggestions while preparing the manuscript for the second edition.

N Kalyanasundaram Jaypee Institute of Information Technology (JIIT), Noida, Uttar Pradesh

G Naveen Babu Gautam Buddha University, Greater Noida, Uttar PradeshDheeraj Kumar Yadav Rajasthan Technical University, Kota, RajasthanGhanshyam Singh, M M Sharma Malviya National Institute of Technology, Jaipur, RajasthanKishore Kumbhave Jawaharlal Institute of Technology,

Khargone, Madhya PradeshSangram Mohapatra C V Raman College of Engineering, Bhubaneshwar, OdishaAdarsh Yadav Government College of Engineering, Kalahandi, OdishaTanushree Bose Roy Sikkim Manipal Institute of Technology, Gangtok, SikkimDeepak Ghodgaonkar Dhirubhai Ambani Institute of Information and

Communication Technology, Gandhinagar, GujaratDhiren Vaghela Gandhinagar Institute of Technology, Kalol, GujaratK Mahadevan PSNA College of Engineering and Technology,

Dindigul, Tamil NaduT Sabapanthi, S T Jaya Christa Mepco Schlenk Engineering College, Sivakasi, Tamil NaduA Marimuthu KLN College of Engineering, Madurai, Tamil NaduSaranya Tamil Nadu Government Engineering College,

Chennai, Tamil NaduT V B Phani Kumar Institute of Aeronautical Engineering,

Hyderabad, Telangana


Preface to the Second Edition xvPreface to the Second Edition xv

C Dharma Raj Gandhi Institute of Technology and Management, Visakhapatnam, Andhra Pradesh

We are also thankful to our family members for their support and patience, which enabled us to go ahead with this project. Finally, we thank our publishers, McGraw Hill Education (India) for bringing out the second edition.

Feedback Request

We shall be grateful to acknowledge any constructive comments/suggestions from the readers for further improvement of the book.

S C MahapatraS Mahapatra

Publisher’s NoteMcGraw Hill Education (India) invites suggestions and comments from you, all of which can be sent to [email protected] (kindly mention the title and author name in the subject line).Piracy-related issues may also be reported.


Preface to the First Edition

Electromagnetics is the study of principles, theory, analysis, computation, and application of electric and magnetic fields, their coexistence, and propagation in unbounded and bounded regions. This is a subject that students generally find difficult to comprehend, especially at the junior undergraduate level. The material in this book, covered in ten chapters, is suitable for a one-semester course, taught in the third or fourth semester, to undergraduate-level electrical engineering, electrical and electronics engineering, and electronics and communications engineering students.

Principles of many electrical and electronic equipment and devices are based on the laws of electric and magnetic fields. Some of these are transformers, rotating and linear electromagnetic apparatuses, electromagnetic instruments and relays, electromagnetic levitation, lifting electromagnets, electrostatic precipitators, electronic display systems, radio direction and range (RADAR), particle accelerators, and resonators. Some other important applications of electromagnetic field laws are in terrestrial, satellite and space communications.

Study of electromagnetics will help students better understand electromagnetic devices, and propose innovative solutions to problems such as electromagnetic interference, and electromagnetic compatibility, encountered in various fields like power systems, wireless communication, and biomedical engineering. A design engineer is required to have the basic knowledge of electromagnetics to understand the design principles involved in connecting cell phones, laptop computers, and personal digital assistants to the Internet through wireless access points using RF signals. Another potential area of application of electromagnetics is the use of RF signals in high performance computer systems for intercomponent data transfer. This book, therefore, aims to assist students in a holistic study of this subject.


Principles of Electromagneticsxviii Preface to the First Editionxviii

What Makes this Book Unique?This book presents the subject in a simple and systematic manner. It adheres to precise explanations of topics to help students grasp concepts better. A number of two-dimensional and three-dimensional illustrations have been included for easy understanding. Mathematical steps have been explained stepwise; leaving the final step, such as differentiation or integration, for the students to work out. Each chapter starts with an introduction, followed by theory and applications. Most of the sections in a chapter start with an introduction. A dedicated chapter on ‘Solution of Boundary-Value Problems’, for both static electric and magnetic fields has been included.

Every chapter contains a number of solved examples to acquaint the students with problem-solving techniques. Summaries and important formulae are given after the main text in all the chapters to aid in quick revision. Questions, problems, and multiple-choice questions given at the end of each chapter will help students in evaluating their understanding of the chapter’s content. Questions have been especially graded with either one, two, or three stars to indicate challenge levels. Answers for selected questions have also been provided. Multiple-choice questions with two answers have been marked with a star.

Book OverviewThe subject has been discussed in a comprehensive manner wherein a chapter each has been dedicated to an important topic. Contents of the book follow a logical flow and are described ahead briefly.

Electric and magnetic field quantities are vectors in three-dimensional space. These are represented by the use of suitable coordinate systems. Moreover, fields varying sinusoidally with time are vectors as well as phasors. For proper understanding of the subject, students should have adequate knowledge of at least three basic coordinate systems, fundamentals of vector analysis, and representation of sinusoidally time-varying quantities. Brief descriptions of these topics are given in Chapter 1.

Chapter 2 covers laws and theorems of electrostatic fields and their applications. Some of the important topics available in this chapter are vector forms of Coulomb’s law and electric field intensity, divergence of electric flux density and divergence theorem, potential gradient, relationship between electric susceptibility and relative permittivity, boundary conditions, energy stored in electric field, and calculation of capacitance for various types of capacitors and transmission lines. The study of electrostatics will help students understand the principles of equipment and devices based on electrostatic laws. Insulation coordination of high-voltage equipment requires calculation of potential gradient in the insulating medium. Calculation of capacitance of transmission lines is necessary to develop their circuit models.

An important relation between electric field intensity and conduction current density, known as point form of Ohm’s law, is derived in Chapter 3. This law, also valid for time-varying fields, is an extension of Maxwell’s equation. The chapter also contains Kirchhoff’s voltage law in terms of field quantities, continuity equation for direct currents, Joule’s law, calculation of insulation resistance, and a brief description of current flow in semiconductors.

Chapter 4 starts with the statement of scalar and vector forms of the Biot–Savart law. The concepts of magnetic flux density and magnetic flux are introduced next. Electromagnetic force on a current-carrying conductor and electromagnetic torque on a current loop are discussed in some detail because of their practical importance. Some other topics covered in the chapter include Ampere’s magnetic


Preface to the First Edition xixPreface to the First Edition xix

circuital law, curl of magnetic field intensity, Stokes’ theorem, relation between magnetic susceptibility and relative permeability, boundary conditions, and energy stored in the magnetic field. The magnetic circuital law is applied for magnetic circuit calculations, which in turn is utilised for calculation of internal inductance, self-inductance, and mutual inductance from the flux-linkage point of view. Knowledge of magnetic circuit calculations is necessary for predetermination of magnetising current of electromagnetic equipments. Development of circuit models of transmission lines, transformers, etc., requires calculation of inductance.

Three techniques for solving boundary-value problems are discussed in Chapter 5. These are closed-form solution of one-dimensional and two-dimensional Laplace’s equation in rectangular and cylindrical coordinates, the image method, and the technique of freehand field mapping. The first two methods are useful for solving only a limited class of problems with boundaries of regular shapes. The graphical technique, however, can be used for problems with any boundary shape. Results obtained from field maps are not accurate. However, they may be used to verify whether results from analytical methods are correct or not.

Time-varying electric and magnetic fields, designated as electromagnetic fields, are described in Chapter 6. The chapter covers Faraday’s law of electromagnetic induction, Maxwell’s equations, Poynting vector, and their applications. The continuity equation, eddy-current loss in a thin iron sheet, displacement current, distribution of current in a round conductor are some other topics included in this chapter. Faraday’s law is used for calculation of induced voltage in conductors and conducting coils both by speed and transformer actions. Maxwell’s equations are applied to derive the Poynting vector, which is used for power calculations. The theories of propagation of electromagnetic waves given in Chapters 7 and 9 are developed using Maxwell’s equations.

In Chapter 7, we use all the important Maxwell’s equations for derivation of wave equations. The chapter contains solution for one-dimensional wave equation in unbounded regions, properties and parameters of uniform plane waves, wave reflection at discontinuities, power calculations using the Poynting vector, and standing wave ratio. The chapter is concluded with descriptions of critical angle of incidence and the Brewster angle.

The analysis of two-conductor uniform long transmission lines used for transmission of electric power and signals is outlined in Chapter 8. The chapter contains derivation of transmission line equations from the circuit model of the line. Solutions of the wave equation, properties and parameters of the line, reflection and transmission of voltage and current at discontinuities, power calculations, standing wave ratio, matching of transmission lines with load are some of the topics covered in this chapter. Two-conductor transmission lines are widely used as links between generators (transmitters) and loads (receivers).

Though two conductors (one may be earth) are generally required for transmission of electric power, electric energy at high frequencies can also be transmitted through a hollow metallic cylinder—the waveguide. Chapter 9 describes wave propagation in a parallel-plate waveguide and through a rectangular waveguide. Solutions of relevant wave equations, various properties and formulae of parameters of the waveguides are included in this chapter. We learn in this chapter that electromagnetic waves in bounded regions can travel in different modes, and wave propagation is possible only above a certain frequency, called the cut-off frequency. The cut-off frequency depends on the distance between the plates of a parallel-plate waveguide, and on the side lengths of the cross section of a rectangular waveguide.


Principles of Electromagneticsxx Preface to the First Editionxx

Chapter 10 describes the principle of launching electromagnetic waves into free space with the help of antennas. We learn in this chapter about various radiation properties of antennas from the analysis of a Hertzian dipole and a half-wave dipole. It is shown that the image of a monopole above a conducting plane or earth is also a monopole, and the actual and the image monopoles combine to form a dipole antenna. A brief study of radiation from antenna arrays is given in this chapter. Working principles of the Yagi–Uda antenna and receiving antennas are also described.

Equations, expressions, and formulae are numbered sectionwise. Equation number, section number, and chapter number are mentioned wherever a reference is made to an earlier equation. For example, (3.11-7) refers to Formula 7 of Section 11 in Chapter 3. Whereas (9) refers to Equation 9 of the same section.

AcknowledgementsWe would like to thank the reviewers mentioned below for their valuable suggestions and comments on the manuscript.

Navneet Gupta Birla Institute of Technology and Science, Pilani, Rajasthan

Abhijit Sarkar Jaipur Engineering College and Research Centre, Jaipur, Rajasthan

D S Kushwaha Kanpur Institute of Technology, Kanpur, Uttar Pradesh

Debparna Sengupta Techno India College of Technology, Kolkata

Sanghmitra Chatterjee Camellia Institute of Technology, Kolkata

S K Behera National Institute of Technology Rourkela, Odisha

P D Kasyap North Eastern Regional Institute of Science and Technology, Nirjuli, Arunachal Pradesh

Ashok Khedkar Cummins College of Engineering for Women, Pune, Maharashtra

Sarosh Dastoor Sarvajanik College of Engineering and Technology, Surat, Gujarat

K T Mathew Viswajyoti College of Engineering and Technology, Vazhakulam, Kerala

P Dananjayan Pondicherry Engineering College, Pondicherry

K Lakshmi K S Rangasamy College of Technology, Tiruchengode, Tamil Nadu

P Chidambara Nathan National Institute of Technology Trichy, Tamil Nadu

K R Subramanian (Retd.) Kumaraguru College of Technology, Coimbatore, Tamil Nadu

M Karthikeyan Paaval Engineering College, Namakkal, Tamil Nadu

T V Prasad Narayan Engineering College, Nellore, Andhra Pradesh

B L Prakash Vignan Institute of Information Technology, Vishakhapatnam, Andhra Pradesh


Preface to the First Edition xxiPreface to the First Edition xxi

We are also grateful to Dr R K Mishra and Dr T Sahu, professors in the Postgraduate Department of Electronic Sciences, Berhampur University, and Dr L K Mahapatra, a mathematician and a senior officer in industries department, Government of Odisha, for their sincere help. We are also grateful to Mr A K Khanda, programmer at the Computer Centre, Berhampur University, for his timely help whenever required.

We thank our family members for their active support and encouragement, which has been of great help in completing this project.

S C MahapatraS Mahapatra


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