Lessons In Electric Circuits Volume I - DC

Lessons In Electric Circuits Volume I - DC

(Parte 1 de 8)

Fifth Edition, last update October 18, 2006 Fifth Edition, last update October 18, 2006

Lessons In Electric Circuits, Volume I { DC

By Tony R. Kuphaldt Fifth Edition, last update October 18, 2006 c©2000-2006, Tony R. Kuphaldt

This book is published under the terms and conditions of the Design Science License. These terms and conditions allow for free copying, distribution, and/or modiflcation of this document by the general public. The full Design Science License text is included in the last chapter.

As an open and collaboratively developed text, this book is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the Design Science License for more details. Available in its entirety as part of the Open Book Project collection at:

w.ibiblio.org/obp/electricCircuits

† First Edition: Printed in June of 2000. Plain-ASCII illustrations for universal computer readability.

† Second Edition: Printed in September of 2000. Illustrations reworked in standard graphic (eps and jpeg) format. Source flles translated to Texinfo format for easy online and printed publication.

† Third Edition: Equations and tables reworked as graphic images rather than plain-ASCII text.

† Fourth Edition: Printed in August 2001. Source flles translated to SubML format. SubML is a simple markup language designed to easily convert to other markups like LATEX, HTML, or DocBook using nothing but search-and-replace substitutions.

† Fifth Edition: Printed in August 2002. New sections added, and error corrections made, since the fourth edition.

i i

Contents

1.1 Static electricityix
1.2 Conductors, insulators, and electron °owxv
1.3 Electric circuitsxix
1.4 Voltage and currentxxi
1.5 Resistancex
1.6 Voltage and current in a practical circuitxxxiv
1.7 Conventional versus electron °owxxxv
1.8 Contributorsxxxix

1 BASIC CONCEPTS OF ELECTRICITY ix

2.1 How voltage, current, and resistance relatexli
2.2 An analogy for Ohm’s Lawxlvi
2.3 Power in electric circuitsxlvii
2.4 Calculating electric powerxlix
2.5 Resistorslii
2.6 Nonlinear conductionlvii
2.7 Circuit wiringlxii
2.8 Polarity of voltage dropslxvi
2.9 Computer simulation of electric circuitslxvii
2.10 Contributorslxxxi

2 OHM’s LAW xli

3.1 The importance of electrical safetylxxxiii
3.2 Physiological efiects of electricitylxxxiv
3.3 Shock current pathlxxxvi
3.4 Ohm’s Law (again!)xci
3.5 Safe practicesxcviii
3.6 Emergency responsecii
3.7 Common sources of hazardciii
3.8 Safe circuit designcvi
3.9 Safe meter usagecxi
3.10 Electric shock datacxxi
3.1 Contributorscxxi

3 ELECTRICAL SAFETY lxxxiii i iv CONTENTS

4.1 Scientiflc notationcxxiii
4.2 Arithmetic with scientiflc notationcxxv
4.3 Metric notationcxxvii
4.4 Metric preflx conversionscxxviii
4.5 Hand calculator usecxxix
4.6 Scientiflc notation in SPICEcxxx
4.7 Contributorscxxxii

4 SCIENTIFIC NOTATION AND METRIC PREFIXES cxxiii

5.1 What are "series" and "parallel" circuits?cxxxiii
5.2 Simple series circuitscxxxvi
5.3 Simple parallel circuitscxlii
5.4 Conductancecxlvii
5.5 Power calculationscxlix
5.6 Correct use of Ohm’s Lawcl
5.7 Component failure analysisclii
5.8 Building simple resistor circuitsclviii
5.9 Contributorsclxxiii

5 SERIES AND PARALLEL CIRCUITS cxxxiii

6.1 Voltage divider circuitsclxxv
6.2 Kirchhofi’s Voltage Law (KVL)clxxxiii
6.3 Current divider circuitscxciii
6.4 Kirchhofi’s Current Law (KCL)cxcvii
6.5 Contributorscxcix

6 DIVIDER CIRCUITS AND KIRCHHOFF’S LAWS clxxv

7.1 What is a series-parallel circuit?cci
7.2 Analysis techniquecciv
7.3 Re-drawing complex schematicsccxi
7.4 Component failure analysisccxix
7.5 Building series-parallel resistor circuitsccxxiv
7.6 Contributorsccxxxvi

7 SERIES-PARALLEL COMBINATION CIRCUITS cci

8.1 What is a meter?ccxxxix
8.2 Voltmeter designccxliv
8.3 Voltmeter impact on measured circuitccxlix
8.4 Ammeter designcclvii
8.5 Ammeter impact on measured circuitcclxiii
8.6 Ohmmeter designcclxvii
8.7 High voltage ohmmeterscclxxi
8.8 Multimeterscclxxix
8.9 Kelvin (4-wire) resistance measurementcclxxxiv
8.1 Wattmeter designccxcvi
8.12 Creating custom calibration resistancesccxcviii
8.13 Contributorsc

CONTENTS v

9.1 Analog and digital signalsccci
9.2 Voltage signal systemsccciv
9.3 Current signal systemscccv
9.4 Tachogeneratorscccviii
9.5 Thermocouplescccix
9.6 pH measurementcccxiv
9.7 Strain gaugescx
9.8 Contributorscccxxvii

9 ELECTRICAL INSTRUMENTATION SIGNALS ccci

10.1 What is network analysis?cccxxix
10.2 Branch current methodcxi
10.3 Mesh current methodcccxl
10.4 Node voltage methodccclvi
10.5 Introduction to network theoremsccclx
10.6 Millman’s Theoremccclx
10.7 Superposition Theoremccclxiii
10.8 Thevenin’s Theoremccclxviii
10.9 Norton’s Theoremccclxxii
10.10 Thevenin-Norton equivalenciesccclxxvi
10.1 Millman’s Theorem revisitedccclxxviii
10.12 Maximum Power Transfer Theoremccclxxx
10.13 ¢-Y and Y-¢ conversionsccclxxxii
10.14 Contributorsccclxxxviii

10 DC NETWORK ANALYSIS cccxxix

1.1 Electron activity in chemical reactionsccclxxxix
1.2 Battery constructioncccxcv
1.3 Battery ratingscccxcviii
1.4 Special-purpose batteriescd
1.5 Practical considerationscdiv
1.6 Contributorscdvi

1 BATTERIES AND POWER SYSTEMS ccclxxxix

12.1 Introductioncdvii
12.2 Conductor sizecdix
12.3 Conductor ampacitycdxv
12.4 Fusescdxvii
12.5 Speciflc resistancecdxxiv
12.6 Temperature coe–cient of resistancecdxxviii
12.8 Insulator breakdown voltagecdxxxiv
12.9 Datacdxxxv
12.10 Contributorscdxxxv

vi CONTENTS

13.1 Electric flelds and capacitancecdxxxvii
13.2 Capacitors and calculuscdxli
13.3 Factors afiecting capacitancecdxlvii
13.4 Series and parallel capacitorscdl
13.5 Practical considerationscdli
13.6 Contributorscdlvi

13 CAPACITORS cdxxxvii

14.1 Permanent magnetscdlvii
14.2 Electromagnetismcdlxi
14.3 Magnetic units of measurementcdlxiii
14.4 Permeability and saturationcdlxvi
14.5 Electromagnetic inductioncdlxxi
14.6 Mutual inductancecdlxxiii
14.7 Contributorscdlxxv

14 MAGNETISM AND ELECTROMAGNETISM cdlvii

15.1 Magnetic flelds and inductancecdlxxvii
15.2 Inductors and calculuscdlxxxi
15.3 Factors afiecting inductancecdlxxxvii
15.4 Series and parallel inductorscdxcii
15.5 Practical considerationscdxciv
15.6 Contributorscdxciv

15 INDUCTORS cdlxxvii

16.1 Electrical transientscdxcv
16.2 Capacitor transient responsecdxcv
16.3 Inductor transient responsecdxcviii
16.4 Voltage and current calculationsdi
16.5 Why L/R and not LR?dvii
16.6 Complex voltage and current calculationsdix
16.7 Complex circuitsdxi
16.8 Solving for unknown timedxvi
16.9 Contributorsdxviii

16 RC AND L/R TIME CONSTANTS cdxcv

BIBLIOGRAPHY dxix A-1 ABOUT THIS BOOK dxxi A-2 CONTRIBUTOR LIST dxxv A-3 DESIGN SCIENCE LICENSE dxxxi

CONTENTS vii INDEX dxxxiv viii CONTENTS viii CONTENTS

Chapter 1

1.1 Static electricityix
1.2 Conductors, insulators, and electron °owxv
1.3 Electric circuitsxix
1.4 Voltage and currentxxi
1.5 Resistancex
1.6 Voltage and current in a practical circuitxxxiv
1.7 Conventional versus electron °owxxxv
1.8 Contributorsxxxix

Contents

1.1 Static electricity

It was discovered centuries ago that certain types of materials would mysteriously attract one another after being rubbed together. For example: after rubbing a piece of silk against a piece of glass, the silk and glass would tend to stick together. Indeed, there was an attractive force that could be demonstrated even when the two materials were separated:

Glass rodSilk cloth attraction x CHAPTER 1. BASIC CONCEPTS OF ELECTRICITY

Glass and silk aren’t the only materials known to behave like this. Anyone who has ever brushed up against a latex balloon only to flnd that it tries to stick to them has experienced this same phenomenon. Para–n wax and wool cloth are another pair of materials early experimenters recognized as manifesting attractive forces after being rubbed together:

attraction

Wool cloth Wax

This phenomenon became even more interesting when it was discovered that identical materials, after having been rubbed with their respective cloths, always repelled each other:

Glass rodGlass rod repulsion

Wax repulsion Wax

It was also noted that when a piece of glass rubbed with silk was exposed to a piece of wax rubbed with wool, the two materials would attract one another:

1.1. STATIC ELECTRICITY xi

Glass rod Wax attraction

Furthermore, it was found that any material demonstrating properties of attraction or repulsion after being rubbed could be classed into one of two distinct categories: attracted to glass and repelled by wax, or repelled by glass and attracted to wax. It was either one or the other: there were no materials found that would be attracted to or repelled by both glass and wax, or that reacted to one without reacting to the other.

More attention was directed toward the pieces of cloth used to do the rubbing. It was discovered that after rubbing two pieces of glass with two pieces of silk cloth, not only did the glass pieces repel each other, but so did the cloths. The same phenomenon held for the pieces of wool used to rub the wax:

Silk clothSilk cloth repulsion repulsion

Wool clothWool cloth

Now, this was really strange to witness. After all, none of these objects were visibly altered by the rubbing, yet they deflnitely behaved difierently than before they were rubbed. Whatever change took place to make these materials attract or repel one another was invisible.

(Parte 1 de 8)

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