A Programmed Review for Electrical Engineering

295 Pages·1985·9.158 MB·English

by  James H. Bentley P.E. (auth.)

A
Programmed
R~view~lor
Electrica
Engineering
A
Programmed
R~viewFor
Electrica
Engineering
Second Edition
JAMES H. BENTLEY, P. E.
Magnetic Peripherals, Inc.
Minneapolis, Minnesota
Programmed by
KAREN M. HESS, Ph. D.
Innovative Programming Systems,lnc.
Minneapolis, Minnesota
Imi5I VAN NOSTRAND REINHOLD COMPANY
~ ------_ New York
Copyright © 1984 by Van Nostrand Reinhold Company Inc.
Softcover reprint of the hardcover 1st edition 1984
Ubrary of Congress Catalog Card Number: 83-21835
ISBN-13:978-94-0l0-8651-6 e-ISBN-13:978-94-009-4860-0
DOl: 10.1007/978-94-009-4860-0
All rights reserved. Certain portions of this work copyright © 1978
by Van Nostrand Reinhold Co. Inc. No part of this work covered by the copyright hereon
may be reproduced or used in any form or by any means-graphic, electronic, or
mechanical, including photocopying, recording, taping, or infonnation storage
and retrieval systems-without the prior written permission of the publisher.
Manufactured in the United States of America
Published by Van Nostrand Reinhold Company Inc.
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New York. New York 10003
Van Nostrand Reinhold Company Limited
Molly Millars Lane
Wokingham. Berkshire RG II 2PY. England
Van Nostrand Reinhold
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Macmillan of Canada
Division of Canada Publishing Corporation
164 Commander Boulevard
Agincourt. Ontario MIS 3C7. Canada
15 14 13 12 11 10 9 8 7 6 5 4 3
Ubrary of Congress Cataloging in Publication Data
Bentley, James H.
A programmed review for electrical engineering.
Includes Index.
1. Electrical engineering-Problems, exercises, etc.
2. Electric engineering-Programmed instruction.
I. Hess, Karen M., 1939-0000. II. Title.
TKI68.B461984 621.3'07'7 83-21835
ISBN -13: 978-94-010-8651-6
Preface
The field of electrical engineering is very innovative-new products and new ideas are continu
ally being developed. Yet all these innovations are based on the fundamental principles of
electrical engineering: Ohm's law, Kirchhoff's laws, feedback control, waveforms, capacitance,
resistance, inductance, electricity, magnetism, current, voltage, power, energy. It is these
basic fundamentals which are tested for in the Professional Engineering Examination (PE
Exam).
This text provides an organized review of the basic electrical engineering fundamentals. It
is an outgrowth of an electrical engineering refresher course taught by the author to candidates
preparing for the Professional Engineering Examination-a course which has enabled scores of
electrical engineers in Minnesota and Wisconsin to successfully pass the PE Exam.
The material is representative of the type of questions appearing in the PE Exams prepared
by the National Council of Engineering Examiners (NCEE) over the past twelve years. Each
problem in the text has been carefully selected to illustrate a specific concept. Included with
each problem is at least one solution. Although the solutions have been carefully checked,
both by the author and by students, there may be differences of interpretation. Also, in some
cases certain assumptions may need to be made prior to problem solution, and since these
assumptions will vary from individual to individual, the final answer may also differ. The
author has attempted to keep the requirements for assumptions and interpretation to a mini
mum. However, since problems requiring this sort of judgment appear in the PE Exam, they
have also been included in this text.
Although the types of questions are similar to those given in past exams, the author cautions
that the NCEE may include questions in future exams that may differ considerably from past
format. Each exam is new, with very little repetition from past exams. However, the purpose
of the exam is to test the examinee's knowledge of electrical engineering fundamentals, and if
the examinee, through experience, education, and review, has command of these funda
mentals, he will have no trouble in passing the exam.
While the material in this text is intended as a programmed review for those preparing for
v
PREFACE
the PE Exam, the material is fundamental to electrical engineering and can provide an excel
lent resource and review for any student or practicing electrical engineer. Rarely does an elec
trical engineer work with all areas of electrical engineering on a daily basis. However, during
the course of an engineer's career, he will probably become involved in nearly every field.
(This has been the author's experience, and the material in this text has proved invaluable on
numerous occasions.)
The author has conducted refresher courses since 1973 using the material contained in the
text. Students have come from such diverse enterprises as 3M Company, General Electric, IBM,
Northern States Power, Univac, Medtronic, Honeywell, Northwestern Bell, the State of Minne
sota, Control Data, and a number of private consulting engineering firms. The author wishes
to thank these students for their valuable suggestions, criticisms, and corrections. Others to
whom the author is deeply indebted include Allen Baldwin, Connie Nelson, Fred Pfeiffer, and
Francis Cook.
James H. Bentley, P.E.
Minneapolis, Minnesota
VI
Introduction
This text reviews electrical engineering fundamentals required to pass the Professional Engi
neering Examination (PE Examination) in Electrical Engineering. It is designed to aid the
electrical engineer in preparation for the PE Examination by presenting an organized review of
materials ordinarily contained in a college electrical engineering curriculum. The primary
emphasis is on problem solving with orientation as close as possible to the type of questions
contained in the exam.
WHY REGISTRATION?
The requirement for engineering registration is continually spreading throughout the United
States. In 1975, 40% of U.S. engineers (nearly 500,000) were registered. Most engineers in
private practice or working for state or local agencies must be licensed. Many engineers in
industry need to be registered to sell their designs and products to certain consumers. While
most states presently exempt engineers in industry from the requirement for registration, the
trend is toward removal of this exemption. As noted by Fran Lavoie, managing editor of
Machine Design (December 26, 1974): "If you hope to rise to a responsible engineering
position, you'll eventually have to be registered. Conversely, the fact that you aren't registered
could cost you a promotion."
Requirements
There are six basic requirements for registration (the specific requirements may vary slightly
from state to state): (1) age-minimum age of 25 for licensing, 21 for Engineer-in-Training;
(2) graduation from an accredited high school; (3) an engineering degree from an accredited
ECPD course of study in an engineering school or its equivalent in practical engineering experi
ence; (4) experience of a minimum number of years, broad in scope and generally requiring
vii
A PROGRAMMED REVIEW FOR ELECTRICAL ENGINEERING
knowledge of engineering mathematics, physical and applied sciences, properties of materials,
and the fundamental principles of engineering design; (5) character references; and (6) ex
amination by the state board of engineers. Some states also require u.S. citizenship.
You should contact your licensing board to obtain the specific requirements for your state
or jurisdiction. The mailing adresses of Member and Affiliate Member Boards may be obtained
from the National Council of Engineering Examiners, P.O. Box 5000, Seneca, SC 29678.
A LOOK AHEAD TO THE PE EXAM
The PE Exam tests an individual's experience and knowledge in his field; it is intended to show
the applicant's ability to apply sound engineering principles and judgment to the solution of
problems encountered in practice.
The exam is divided into two four-hour periods. You must work four problems during each
period: four engineering during one period, and one economics and three engineering during
the other period. (In some states the economics problem is optional and may be replaced by
a fourth engineering problem.) During each four-hour period there are ten engineering prob
lems from which to select. The major categories which may be covered during the eight-hour
examination are:
• power and systems
• machines
• electronics
• communications
• circuits
• controls
• economics
• instrumentation
• illumination
• logic
The PE Exam is straightforward. There are not trick questions. You are either familiar with
a particular problem or you are not. Therefore, before working any engineering problems,
read them all and eliminate those with which you are least familiar. Select the problems that
best fit your background and work them. (You ·have an average of one hour per problem.) Do
the easiest problems first; concentrate the remainder of your time on the more difficult ones.
Try not to make any computational errors. However, if you do make an error, partial credit is
given if your basic approach is correct. Therefore, it is important to show your method of
solution as well as all your work.
PREPARATION
Like anything done well, taking the PE Exam requires thorough preparation. Seldom can a
person walk into the exam with little or no preparation and expect to pass.
To do well on the exam, allocate yourself about ten weeks of review time. Read a chapter
from this text each week. Work all the problems. Then rework them. Refer to your college
texts for other problems and background material. Allocate the week before the exam for a
viii
INTRODUCTION
general review. You may concentrate your efforts in areas you are most familiar, but do not
expect the PE Exam to include questions in every area of electrical engineering. It is best to be
familiar with as many areas as possible. One time the PE Exam may have several problems on
machinery or control theory, and six months later there may be none.
What to Take Along
Most states administer an open book examination. Your state board will let you know what
you can use during your examination. Some examinees take a suitcase or two of reference
books, but usually only one or two of these books is actually used. Some problems require use
of handbooks, but general textbooks usually are not needed.
The following is a recommended list of basic items to take to the exam (if permitted by
your board of registration):
• CRC Standard Mathematical Tables
• Reference Data for Radio Engineers
• a general electrical engineering handbook
• an electrical engineering review book (this text might be used)
• a calculator (fully charged)
• compass and straight edge (for Smith chart problems)
• six sharp pencils with good erasers
A SYSTEMATIC, PROGRAMMED REVIEW
This text is organized to provide a logically sequenced review of electrical engineering and
economics. It is designed around problems and provides the necessary information needed to
solve the problems in the form of tables, formulas, charts, and graphs. It does not contain
background material that can be found in other texts and handbooks. Where background
material is desired, the reader is directed to other source material. An extensive bibliography
is also included. The serious reviewer will refer to other texts and handbooks for derivations
of formulas and other background materials needed for a complete review.
The first chapter of the text introduces the basic principles of electrical engineering. The
second chapter is devoted entirely to problems related to these fundamental principles. It is
intended as an applied review of basic circuits and the concepts presented in the first chapter.
The remaining chapters cover the several specific areas of electrical engineering where mathe
matical and graphical techniques supplement the fundamental concepts. In these chapters a
discussion of background materials needed for solving problems is normally given. The last
i
chapter deals with economics, a subject representing of most PE Examinations.
The book is based on problems, just as is the PE Exam. Discussion is included to introduce
a subject and to provide the background necessary to solve a particular problem. In some
instances a general discussion precedes one or more problems, in which case the problems refer
back to the discussion. In other cases, a problem will be self-contained; the solution given for
the problem will contain all the needed information; no reference will be made to preceding
discussions.
The text attempts to include problems that, in toto, illustrate nearly every concept and every
IX
A PROGRAMMED REVIEW FOR ELECTRICAL ENGINEERING
type of question asked on the NCEE-prepared PE Exam during the past eighteen years. In some
cases the problems included are subsets of past PE Exam problems, broken down to illustrate
specific points. A PE Exam problem can comprise the contents of several of the problems
presented in this text. There may also be variations on a particular problem. No one but the
NCEE knows what questions will be on the next PE Exam until the time of the exam.
This text omits two areas sometimes included in the PE Exam-illumination and national
electric code-and it includes one area covered very seldom in the PE Exam-logic. Illumina
tion is not covered here because very few engineers are involved in the field, it is not included
in traditional electrical engineering curricula, and it is based more on aesthetics and empirical
data than on fundmentals. Similarly, national electric code problems are not included because
they apply only to a limited number of engineers. Examinees working in either of these fields
will have the necessary experience and handbooks to solve the problems. Others may simply
skip these problems.
Logic is covered because a significant number of electrical engineers use digital techniques
in their work. Logic touches the lives of nearly everyone and has an important impact on an
individual's health and safety. Although problems in this area have rarely been included on
past exams, recent PE Exams have included logic problems, and it is likely that most future
exams will include them.
x
Contents
Preface v
Introduction vii
1 FUNDAMENTAL CONCEPTS OF ELECTRICAL ENGINEERING 1
Introduction 1
Electrical Quantities 2
Ohm's Law 5
Circuit Elements Defined 5
Circuit Element Values 7
Coulomb's Law 9
Series and Parallel Combinations 10
Wye-Delta (Y -M Transformation 11
Complex Algebra 11
Complex Notation 12
Circuit Element Equations 12
Transients 13
Laplace Transform 16
Kirchhoff's Laws 17
Thevenin's Theorem 17
Maximum Power Transform Theorem 18
Maximum Power Transform Theorem Corollary 19
Norton's Equivalent Circuit 19
Voltage Division and Superposition 20
Magnetic Circuit Terms 20
Determinants 21
xi