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Electromagnetics , Second Edition Kraus and Carver

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Electromagnetics, Second Edition Kraus and Carver

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The wide and continued use of the first edition of Electromagnetics, including a foreign translation, has given us the incentive to prepare a second edition. Many users have told us of features they wish to have retained in a new edition. But new advances and changes in emphasis and teaching methods have made the addition of new material and revision of the old desirable. The aim of the book, as before, is to present the basic elements of electromagnetic theory for an introductory fields course. The topics have been selected from a wide variety of subjects, but these have been chosen to illustrate important concepts without becoming encyclopedic. As prerequisites the student is assumed to have a knowledge of introductory physics and mathematics through differential and integral calculus. Also a course in vector analysis is essential either beforehand or concurrently.

The introduction (Chap. 1) includes sections on units and dimensions, dimensional analysis and two teaching aids: Thumbnail Electromagnetics and SPEMP chart. Modernized metric (SI) units and nomenclature are used throughout the book. The five chapters (2 to 6) on static electric and magnetic fields and steady currents form the foundation of field theory. Three chapters (7 to 9) discuss boundary- value problems, time-changing fields, and the relation of field and circuit theory, culminating in Max- well's equations. Problem solutions by a variety of methods including analytical, graphical, and computer (both digital and analog) are discussed. Chapters 10 to 12 cover waves in dielectric and conducting media, wave polarization and wave reflection, refraction, and diffraction. Treatments using both physical optics (wavefront) and geometrical optics (ray-path) methods are included. Chapters 13 and 14 explain transmission lines, waveguides, resonators, antennas, and radiation. New sections in these chapters include such topics as bandwidth, time-domain reflectometry, aperture concepts, array theory, radar equation, antenna temperature and radio telescopes. Chapters 15 and 16 treat particles, plasmas, moving systems, and space-time (or relativity). Topics in these chapters include particles in static electric and magnetic fields, wave propagation in a magnetized plasma, Faraday rotation, magnetohydrodynamic (MHD) waves, the space-time concept, fields of a moving system, and radiation pressure. It is shown that there is no such thing as a pure electric or magnetic field which retains its identity for all observers. With the increasing emphasis on outer space and systems in relative motion, these ideas are of fundamental importance. Appendix A contains tables of important constants, equations, and formulas. There is also a very complete tabulation of units and their equivalents. Appendix B is a brief bibliography, and Appendix C gives answers to the starred problems. There is a complete listing of symbols inside the front cover and some frequently used vector relations inside the back cover.

Almost half of the illustrations are new. The problem sets, which are completely revised and expanded, are an important feature of the new edition. Many extend or supplement the text. Among the wide variety of problems included are many which pertain to modern real-world engineering situations, e.g., problems involving a study of engineering feasibility and/or the design of an operational device. Some of these have multiple or indefinite solutions (few real-world problems have exact answers). Such problems can be used for class discussion or term papers. There are also many problems of the more conventional type, yielding definite numerical answers with all gradations of difficulty. A considerable number of problems are arranged for solution by computers. Answers are given to one-half of the problems. There is much to be gained by becoming familiar with the problems, whether one intends to solve them or not. Many topics are included which are not discussed elsewhere in the book and some very interesting and thought-provoking ideas are presented. We recommend "problem reading for pleasure."

The worked examples, numbering about 100, are valuable instructional aids. These examples are of great assistance in understanding the theory and how to apply it to practical situations. The book is designed to provide flexibility for course needs in introductory field theory. There is adequate material for a one-year course. The material is also well adapted for shorter courses. For example, a short course can cover the first six, seven, eight, nine or ten chapters either completely or with the omission of all or part of the following sections: 3-14 through 3-22; 4-14; 4-15; 4-16; 5-25, 5-26; 6-12 through 6-24; 7-10 through 7-17; 10-10; and 10-13 through 10-21. Another option for a short course is to omit all or most of these sections but to include parts of Chaps. 13 to 16; for example, Sees. 13-1 through 13-6 (transmission lines); 14-1, 14-2, 14-5, 14-6, and 14-7 (antenna aperture and array theory); 15-2 and 15-3 (charged particles); and 16-2 (simultaneity). Still other options are possible. Antennas are remarkable in that they can interface between a circuit and space, and some familiarity with them is desirable even in a short fields course. The antenna sections (14-1, 14-2, 14-5, 14-6, and 14-7), indicated above, use nothing more advanced than phasor addition.

Although great care has been exercised, some errors in the text or figures are inevitable. Anyone finding them will do us a great service by writing us so that they can be corrected in subsequent printings.

We are grateful to many teachers and a generation of students who have used the first edition and have generously supplied us with comments and suggestions. Professor Charles F. Fell, University of Nevada, made many recommendations and is responsible for the definitions of idealness, staticness, etc., used in Sees, 2-3 and 2-5. Professor Clarence W. Schultz, University of Connecticut, offered numerous suggestions and supplied the method used with Fig. 6-6 for developing the relation between B, H, and M. We are much indebted to Professors Chen-To Tai, University of Michigan, and John N. Cooper, Navy Post Graduate School ; and Professors Louis L. Bailin, John D. Cowan, Jr; Daniel B. Hodge, Hsien Ching Ko, Curt A. Levis, Edward M. Kennaugh, Robert G. Kouyoumjian, William H. Peake, Leon Peters, Jr., Jack H. Richmond, and Thomas A. Seliga of The Ohio State University. The suggestions by several anonymous reviewers chosen by the publisher were also most useful.

Finally, one of us (J. D. K.), expresses his sincere appreciation to his wife, Alice, for her assistance on the manuscript and for her patience and encouragement during the years of its preparation.



1 Introduction
2 The Static Electric Field: Part 1
3 The Static Electric Field: Part 2
4 The Steady Electric Current
6 The Static Magnetic Field of Ferromagnetic Materials
7 Laplace's and Poisson's Equations and Boundary-value Problems
8 Time-changing Electric and Magnetic Fields
9 The Relation between Field and Circuit Theory; Maxwell's Equations
10 Plane Waves in Dielectric and Conducting Media
11 Wave Polarization
12 Wave Reflection, Refraction, and Diffraction
13 Transmission Lines, Waveguides, and Resonators
14 Antennas and Radiation
15 Particles and Plasmas
16 Moving Systems and Space-Time
Appendix A Units, Constants, and a Few Mathematical Relations