Basic Electronics E-Book

Sean Westcott

• Herausgeber: Packt Publishing
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 372

Veröffentlichungsjahr: 2024

Beschreibung

This updated edition introduces students and hobbyists to electronics, covering microcontrollers, sensors, and wireless communication. Each chapter includes a lab, progressing to building a robot with Arduino and Netduino. New material on Raspberry Pi and Python is included, with companion files featuring videos and code samples.
The course begins with basic electronics concepts, building circuits, and understanding components. It covers digital theory and practical applications with sensors, motors, and microcontrollers. Topics include electricity theory, currents, circuits, tools, safety, and components like resistors, capacitors, diodes, and transistors. Advanced topics include power supplies, soldering, digital theory, integrated circuits, memory, and microcontrollers.
These concepts are crucial for innovation in electronics. This book transitions readers from basic labs to constructing a robot using open-source hardware. It covers Raspberry Pi projects and explores cybersecurity and IoT. Appendices include math for electronics, a timeline of innovations, careers in electronics, and a glossary. This guide provides both theoretical knowledge and practical skills, making it invaluable for mastering electronics.

Leseprobe

BASICELECTRONICS

Third Edition

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BASICELECTRONICS

Theory and Practice

Third Edition

SEAN WESTCOTTJEAN RIESCHER WESTCOTT

MERCURY LEARNING AND INFORMATION

Dulles, VirginiaBoston, MassachusettsNew Delhi

Copyright ©2020 by MERCURY LEARNING AND INFORMATION LLC. All rights reserved.

This publication, portions of it, or any accompanying software may not be reproduced in any way, stored in a retrieval system of any type, or transmitted by any means, media, electronic display or mechanical display, including, but not limited to, photocopy, recording, Internet postings, or scanning, without prior permission in writing from the publisher.

Publisher: David PallaiMERCURY LEARNING AND INFORMATION22841 Quicksilver DriveDulles, VA [email protected][phone]

S. Westcott and J. R. Westcott. Basic Electronics: Theory and Practice. Third Edition.ISBN: 978-1-68392-528-6

The publisher recognizes and respects all marks used by companies, manufacturers, and developers as a means to distinguish their products. All brand names and product names mentioned in this book are trademarks or service marks of their respective companies. Any omission or misuse (of any kind) of service marks or trademarks, etc. is not an attempt to infringe on the property of others.

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CONTENTS

Introduction

About the Authors

Part 1:

The Fundamentals

Chapter 1:

The Theory Behind Electricity

Atoms and Their Structure

Electrons

Valence Shell

Conductors, Insulators, and Semiconductors

Conductors

Insulators

Semiconductors

Electron Flow Versus Hole Flow

The Least You Need to Know

Chapter Review Questions

Chapter 2:

How Electricity Works

Circuits

Electromotive Force or Voltage

Current

Resistance

Ohm’s Law

Power

Joule’s Law

Putting It All Together

The Least You Need to Know

Chapter Review Questions

Lab 2-1: Constructing a Simple Circuit

Chapter 3:

Currents and Circuits

Direct Current

Alternating Current

The War of Currents

Waveforms

Sine Wave

Other Waveforms

Phase

Using Waves to Measure AC Voltage

Direct Current Waveforms

More About Circuits

Circuit Diagrams

Short Circuits

Fuses and Circuit Breakers

Serial and Parallel Circuits

Learning the Language of Electronics

The Least You Need to Know

Chapter Review Questions

Part 2:

Your Workspace and Tools

Chapter 4:

Tools of the Trade

Essential Hand Tools

Essential Instruments

Lab 4-1: Taking a DC Voltage Reading

Lab 4-2: Taking an AC Voltage Reading

Lab 4-3: Measuring Resistance

Lab 4-4: Measuring Current

Electronics Specialty Items

Essential Safety Items

The Least You Need to Know

Chapter Review Questions

Chapter 5:

Shop Setup and Safety

A Clean, Well-Lit Workshop

Claim Your Space

Your Workbench

Adequate Power

Lighting

Ventilation

Storage

Safety Equipment

Good Work Habits Are Good Safety Habits

Come Ready to Work

Dress for the Job

Be Neat and Work Deliberately

Know How Electricity Flows

First Aid for Electrical Shock

The Least You Need to Know

Chapter Review Questions

Part 3:

Electronic Components

Chapter 6:

Switches

Switch Symbols

Mechanical Switches

Poles and Throws

Lab 6-1: SPDT Switch

Push-button Switches

Knife Switches

Bi-metal Switches

Mercury Switches

Other Mechanical Switches

DIP Switches

Electromagnetic Switches or Relays

The Least You Need to Know

Chapter Review Questions

Chapter 7:

Resistors

The Mighty Resistor

Fixed-Value Resistors

Resistor Color Codes and Power Ratings

Reading the Code

Power Ratings

Surface Mount Resistors

Single in Line Resistors

Variable Resistors

Kirchhoff’s Laws

Calculating Resistance

Lab 7-1: Using Ohm’s & Kirchhoff’s Laws to Determine the Proper Resistor

Resistors in Series Circuits

Lab 7-2: Resistors in a Series Circuit

Resistors in Parallel Circuits

Lab 7-3: Resistors in a Parallel Circuit

Voltage Division Circuits

Lab 7-4: Voltage Division Using Fixed Value Resistors

Lab 7-5: Voltage Division Using a Variable Resistor

The Least You Need to Know

Chapter Review Questions

Chapter 8:

Capacitors

How a Capacitor Works

Farads

Relative Permittivity

Capacitor Ratings

Nominal Value and Tolerance

Temperature Coefficients

Breakdown Voltage or DC Working Voltage

Polarized Capacitor Types

Electrolytic Capacitors

Tantalum Capacitors

Non-polarized Capacitor Types

Variable Capacitors

Capacitors in a Circuit

Transient Time of Capacitors in a DC RC Circuit

Lab 8-1: Charging Capacitance

The Least You Need to Know

Chapter Review Questions

Chapter 9:

Diodes

How Diodes Work

Types of Semiconductor Diodes

Common Silicon Diodes

Zener Diodes

Schottky Diodes

Power Rectifiers

Light-Emitting Diodes (LEDs)

Photodiodes

Handling Diodes

The Least You Need to Know

Chapter Review Questions

Chapter 10:

Transistors

Bipolar Junction Transistors (BJTs)

How Amplifiers Work

BJTs Under Varying Voltages

Gain

Darlington Pairs

Field Effect Transistors

Lab 10-1: Using a Transistor to Amplify Current

The Least You Need to Know

Chapter Review Questions

Chapter 11:

Power Sources and Power Supplies

Batteries

How Batteries Produce Energy

Primary vs. Secondary Batteries

Voltages in Batteries

Lab 11-1: Making a Potato Battery

Batteries in Series and in Parallel

Amp-hours

AC-to-DC Power Supplies

Transformers

Variable DC Power Supplies

Uninterruptible Power Supplies

Switched-Mode Power Supplies

The Least You Need to Know

Chapter Review Questions

Part 4:

Getting to Work

Chapter 12:

Soldering

Solder

Lead-free Solder

Flux

Soldering Iron and Tips

Heat Sink

Circuit Boards

Printed Circuit Boards

Prepping for Soldering

Place the Items on the Board

Prepare Your Soldering Iron

Soldering Technique

Desoldering

The Least You Need to Know

Chapter Review Questions

Chapter 13:

Constructing a Power Supply

Power Supply Kit and Construction

Safety First

Powering On

Getting Acquainted with Your Power Supply

Creating a Positive DC Wave

Seeing Caps and Voltage Regulators in Action

Using Your Variable DC Power Supply

The Least You Need to Know

Chapter Review Questions

Part 5:

Going Digital

Chapter 14:

Digital Theory

The Idea Behind Digital Concepts

Analog vs. Digital

Truth Tables

Binary Numbers

Application to Electronics

Logic Gates

Lab 14-1: AND Gate

Lab 14-2: OR Gate

A Revolution Requiring Attention to Detail

The Least You Need to Know

Chapter Review Questions

Chapter 15:

Integrated Circuits

Analog ICs

Digital ICs

Flip-flops

555 and 556 Timers

Counters

Encoders and Decoders

Mixed Signal ICs

Lab 15-1: Building a Decoder Circuit, Part 1

Lab 15-2: Building a Decoder Circuit, Part 2

Lab 15-3: Guitar Amplifier

The Least You Need to Know

Chapter Review Questions

Chapter 16:

Memory

Digital vs. Analog Memory Storage

Parity Bits and Other Error Detection

Hexadecimal

Data and Address

The Von Neumann Computer Model

Memory Registers

Writing and Reading

Volatile and Nonvolatile Memory

Storage Media

The Least You Need to Know

Chapter Review Questions

Chapter 17:

Microcontrollers

What Are Microcontrollers?

Microcontroller Components

Inputs/Outputs

Programming Microcontrollers

Microcontrollers for Hobbyists

Open Source Hardware

The Arduino Microcontroller Platform

The Netduino Microcontroller Platform

The Least You Need to Know

Chapter Review Questions

Part 6:

Electronics in Practice

Chapter 18:

Motors and Controllers

Brushed DC Motors

Brushless DC Motors

Stepper Motors

Servo Motors

Controllers

Pulse Width Modulation

H-bridge

The Least You Need to Know

Chapter Review Questions

Chapter 19:

Sensors

What Is a Sensor?

Electronic Sensors

Accelerometers

Digital Compasses or Magnetometers

Light and Color Sensors

Microphones

Alcohol and Other Environmental Gas Sensors

GPS Sensors

The Least You Need to Know

Chapter Review Questions

Chapter 20:

Electronic Communication

The Basics of Electronic Communication

The Electromagnetic Spectrum, Revisited

Radio Waves

Microwaves

Infrared

Visible Light

Ultraviolet, X-Rays, and Gamma Rays

Encoding and Decoding a Signal

Amplitude Modulation

Frequency Modulation

Phase Modulation

Rasterization

Lab 20-1: Building an FM Stereo Transmitter

The Least You Should Know

Chapter Review Questions

Part 7:

Constructing a Robot and Using Raspberry Pi

Chapter 21A:

Arduino: Building Your Robot

Shopping for Your Robot

Get the Software You Need

Connecting Your Arduino and Getting to Work

Chapter 21B:

Netduino: Building Your Robot

Shopping for Your Robot

Get the Software You Need

Connecting Your Netduino and Getting to Work

Downloading to the Netduino Microcontroller

Chapter 22A:

Arduino: Getting Your Robot Moving

Get Your Motor on Board

Assembling the Motor Driver Shield

Power It Up

Programming Your Robot to Start and Stop

Identifying the I/O Pins

Assembling the Robot Platform

Chapter 22B:

Netduino: Getting Your Robot Moving

Get Your Motor on Board

Assembling the Motor Driver Shield

Power It Up

Programming Your Robot to Start and Stop

Identifying the I/O Pins

Adding Speed Control

Assembling the Robot Platform

Chapter 23A:

Arduino: Adding Sensors to Your Robot

Adding Collision Control

The Ultrasonic Range Finder

Lab 23: Sensing Distance

Adding the Sensor to Your Robot

Adding a Power Switch

Planning and Writing the Code

Arduino Code

Letting Your Robot Roam

Chapter 23B:

Netduino: Adding Sensors to Your Robot

Adding Collision Control

The Ultrasonic Range Finder

Lab 23-1: Sensing Distance

Adding the Sensor to Your Robot

Adding a Power Switch

Planning and Writing the Code

Letting Your Robot Roam

Chapter 24:

Using Raspberry Pi in Your Electronics Projects

Setting up Your Raspberry Pi with an OS

Adding Inputs and Outputs (I/O) to Your Pi

Using the Python Command Shell

Programming with Python on the Pi

Programming a Button in Python

Controlling an LED with the Button

Going Forth

Chapter 25:

Cybersecurity and the Internet of Things (IoT) for Electronics Projects

The Security Challenge

Controlling the Risk

Resources for Securing Your Device

Security Is All of Our Responsibility

Chapter Review Questions

Appendix A:

Glossary

Appendix B:

Timeline of Electronics

Appendix C:

Mathematics for Electronics

Appendix D:

Careers in Electronics

Appendix E:

Resources

Appendix F:

Answers for Odd-Numbered Questions

Appendix G:

Lab Videos, Animations, and Supplementary Video Directory

Index

INTRODUCTION

The study of electronics can be a little overwhelming when you start out. But without assuming that you remember everything from your general science classes, we take you through it all step by step so that you will gain confidence in your understanding of the material. This doesn’t mean that we give you an oversimplified version of electronics, but it does mean that we cover the topics in a more digestible style. We believe that by making the effort to wrap your head around some of the more difficult topics, you will find it easier to progress into further study of electronic theory or hands-on experimentation.

We believe that a new revolution is under way. Electronics has always had a thriving hobbyist population, especially in the 1960s and the 1970s. There were magazines, corner electronics stores; and clubs where enthusiasts could meet and share their creations. It had its subcultures from amateur radio enthusiasts to model rocket builders. In the 1980s, this culture grew to include people building personal computers before such companies such as IBM and Apple began to mass produce them.

The hobbyist field changed as electronics advanced. The increasing sophistication and miniaturization of electronic components and the products built with them made hobbyist-built electronics pale in comparison to their flashier, mass-produced competition. But those same advances are now putting the design and production back into the hobbyists’ hands. Perhaps egged on by battling robots out of university engineering departments, a new generation of electronics buffs is tinkering with technology. With affordable microcontrollers and a wide range of products and information available online, the hobbyist can design and build machines that recharge the ideas of homebrew and do-it-yourself. We can all become Makers.

HOW THIS BOOK IS ORGANIZED

Part 1: The Fundamentals covers electronics basics from the atoms up. You learn about currents, AC and DC voltage, and find out how they all work together to power our world.

Part 2: Your Workspace and Tools introduces the tools of the trade, from the low-tech soldering iron that makes your connections to the high-tech digital multimeter, and offers advice for setting up a shop and working with electricity safely.

Part 3: Electronic Components gives you the nitty-gritty on circuits, capacitors, diodes, transistors, and power supplies. These components are the workhorses of electronics, keeping things powered, amped up, and running smoothly.

Part 4: Getting to Work keeps you busy soldering parts together and creating your own power supply. Once you have these skills under your belt, you’re ready to start building—and inventing—your own electronic devices.

Part 5: Going Digital teaches you to think like a computer. You learn how integrated circuits put digital signals to work and how to use memory to store the instructions that run your gadgets.

Part 6: Electronics in Practice covers motors and controllers, sensors and electronic communication.

Part 7: Constructinga Robot (covering both Arduino and Netduino) helps you use everything you learned from the previous parts to create your own robot—one that can move on its own and sense its environment. What will you build next?

Chapter 25: Cybersecurity and the Internet is a short chapter highlighting your devices and your role in protecting the Internet of Things.

The Appendices provide you with a glossary, a timeline of electronics, a review of mathematics, careers in electronics, electronics resources, answers to the odd-numbered exercises, and the directory of video labs included on the companion files.

EXTRAS

Throughout the book, you will find the following sidebars offering additional insights:

Definitions.

Sometimes it helps to have things stated just a little more directly. In these sidebars, we save you from having to grab a dictionary.

Titans of Electronics.

Not just a parade of historical figures—here we invite you to put yourself in their shoes. These sidebars offer a closer look at the folks who looked at things a little differently and changed the world with their ideas.

High Voltage!

When handled safely, electricity can be safe. But the consequences of not respecting its potential for harm are serious. The more you understand how electricity moves, the better you can prepare and work safely with it.

Wattage to the Wise.

Here you will find straightforward advice—sometimes practical, sometimes more philosophical.

ACKNOWLEDGMENTS

We would like to thank the people who helped us bring this book to publication, Jen Blaney, Kelly Lee, and David Pallai.

We would also like to thank our colleagues and especially our family for supporting us as we worked through many beautiful weekends. The readers and contributors to the Netduino forums provided excellent advice. Special thanks are extended to Bob Godzwon and John O’Brien of Extech Instruments who provided valuable help as technical reviewers of a previous version of this text.

Most importantly, we thank the instructors who have used previous editions of this book and the readers who have reached out with corrections. We are thankful for your appreciation for the place this book attempts to fill, an introduction to concepts that doesn’t require a lot of previous knowledge of electronics, but that can get you to the hands-on work of making your own projects and further study. Your feedback is important and appreciated.

ABOUT THE AUTHORS

Sean Westcott has always loved taking things apart and tinkering with electronics, especially radios, TVs, film cameras, and anything to do with music. He has built his own effects pedals, helped build his friends’ home studio, and apprenticed his way into a gig doing live sound reinforcement in and around Washington, DC. After high school, he studied electronics and moved from the world of bench technician and quality control to computer network technician when the world was changing over from analog to digital technology. He has had a satisfying career supporting computer users and networks since the Internet began changing the workplace and now protecting them working in cybersecurity. He loves what he does and loves sharing his knowledge with others.

Jean Riescher Westcott has been more the book geek, but is no stranger to technology. She spent a summer course learning BASIC programming in a mainframe/terminal environment during high school and fulfilled part of her math requirement in her undergraduate study by taking a class on the history of computers. She moved to a career in books after studying law at American University. Her passion for books, reading, and science led to her first computer book buyer position at an independent bookstore chain in the District of Columbia; she now works in publishing.

Sean and Jean co-wrote Digitally Daunted: The Consumer’s Guide to Taking Control of the Technology in Your Life (Capital Books, 2008), The Complete Idiot’s Guide to Electronics 101 (Alpha, 2011) and two earlier editions of Basic Electronics for Mercury Learning. Jean has co-authored Video Game Addiction (Mercury Learning, 2018) and Industrial Automation and Robotics (Mercury Learning, 2016).

PART

1

THE FUNDAMENTALS

Electronics involves controlling the invisible. Most of the time, you see the effect of electricity but not the actual movement of electric current. This part pulls back the curtain on that hidden world to give you a peek at how electricity works at the atomic level.

It all starts with tiny, charged particles called electrons. You’ll learn how and why electrons move in the natural world and how people have harnessed their power using circuits.

No overview of electronic theory would be complete without an explanation of how current (the flow of electrons, also known as electricity), voltage (the “push” that is caused by the attraction of positive to negative), and resistance (the “push back” of insulators) work. You will find out what power really means and the ways that all of these forces interact.

CHAPTER 1

THE THEORY BEHIND ELECTRICITY

In This Chapter

•Understanding atomic structure

•Harnessing the laws of attraction and repulsion

•Controlling the flow of electrons

•Identifying an element’s conductivity and resistance

Electronics is the study of devices that can control the flow of electricity. You can build devices that detect, measure, power, control, count, store, and transmit electricity—and much more. But in order to do all of these things, you first need to know what electricity is and how it flows.

To get to the essence of electricity, you must delve into some of the most basic concepts in physics: atoms and their structure.

Atoms and Their Structure

An atom consists of a cloud of negatively charged electrons surrounding a dense nucleus that contains positively charged protons and electrically neutral neutrons. The relationship between an atom’s charged particles—its protons and its electrons—is the key to electricity (much more on this in the following sections of this chapter). Atoms are basic units of matter.

Matter refers to any physical substance; in other words, matter is anything that has mass (measurable stuff) and volume (measurable occupation of space).

Ever wonder about the difference between an electric-powered device and an electronic device? It comes down to a matter of language and general usage. Most of us think of things with basic controls only—such as a lamp, iron, or fan—as electric appliances. Devices with more complex control are viewed as electronic devices.

In this book, we first consider most basic controls, such as switches and fuses, and then look into how other electronic components use electricity to perform more sophisticated functions.

A chemical element is pure matter consisting of only one type of atom. Every element is composed of an atom with a particular atomic structure that defines it; for instance, the element carbon is composed exclusively of carbon atoms. Elements are ranked by their atomic number on the periodic table of chemical elements. The atomic number indicates the number of protons in each atom.

The standard model of an atom has an equal number of protons, neutrons, and electrons, but this isn’t always the case. The number of neutrons can vary, and each variation is a different isotope of that element. We call the combined number of protons and neutrons nucleons. For example, carbon-14 is an isotope of carbon. It has six protons and eight neutrons. It is still carbon, but the variation in the number of neutrons affects some of its properties.

FIGURE 1.1 A helium atom.

FIGURE 1.2 The periodic table of elements.

The periodic table of chemical elements, often simply called the periodic table, lists the 118 known elements and basic information—atomic number, relative atomic mass (also known as atomic weight), symbol, and other information, depending on the table—about each element.

Electrons

The atomic number of an element indicates the number of protons. For an electrically neutral or stable atom, the number of protons and electrons are equal, which means that once you know the atomic number of an element you know the number of electrons it has. Electrons travel around the nucleus of the atom in an area known as a shell. Shells are layered outward from the nucleus. Each shell can hold up to a maximum number of electrons. The innermost shell can hold 2 electrons, the second shell can hold 8, the third shell can hold 18, and the fourth can hold 32.

The following table shows the electron arrangements for some common elements:

Valence Shell

The outermost shell of an atom is known as the valence shell (or valence band), and the electrons that inhabit that outer shell are called valence electrons. The more full the valence shell, the less likely it is that an atom will lose electrons when a force is applied. The less full the valence shell, the more likely it is to lose electrons when a force is applied.

Let’s compare two elements. As you can see from the preceding table, neon has a full valence shell, meaning that it is unlikely to gain or lose electrons. Copper, on the other hand, has just 1 electron in its valence band, which can hold 32 electrons. This lone electron filling the valence shell is easily attracted away to a nearby atom that has room on its valence shell.

If a valence shell loses or gains an electron, the atom becomes an ion. An ion is an atom with a charge. An atom that has more protons than electrons has a positive charge. An atom with more electrons than protons has a negative charge. Because of the electromagnetic force, negatively charged electrons will leave their own valence shell to travel to another atom that has a positive charge.

Electromagnetic force (emf) is that attraction between positive and negative charges and the repulsion of like charges. It is the basis of the interaction between the protons and electrons within atoms holding them together, and the attraction between atoms that have negative and positive charges.

Here’s where electricity enters the picture: The movement of electrons on the valence shell when leaving or joining another atom creates electrical current, or electricity. The movement of electrons (and therefore electricity) relies on the two basic concepts that result from the electromagnetic force: 1) opposite charges are attracted to each other; and 2) like charges repel each other.

In his pioneering work on electricity, Benjamin Franklin described something that produced electricity as positive (positive because it gave current) and the recipient material of that current as negative (because it was receiving the electrical charge). This is called conventional theory—the early belief that current traveled from positive to negative.

Today we know now that the opposite is true: Current travels from negative to positive. This is called electron theory.

Confusingly enough, many diagrams that are used to describe circuits show the flow of current in conventional notation, with current flowing from the positive terminal of a battery to the negative terminal. Others use the more accurate electron notation. History creates traditions; we sometimes have to learn to go with the flow!

Conductors, Insulators, and Semiconductors

Some atoms are more stable (or neutral) than others. Stable atoms have an equal number of positively charged protons and negatively charged electrons. The attraction between protons with positive charges and electrons with negative charges holds the atom together unless a force is introduced to separate them.

Conductivity is the tendency of a material to allow the free flow of electrons. Resistance is the opposite; it is the tendency of a material to resist the flow of electrons. When we measure conductivity, we refer to it as resistance. A good conductive material is simply said to have very low resistance. The conductivity of a material is determined by how full or empty the valence shell of its atoms is.

An atom with a full valence shell is not going to accept extra electrons, while an atom with a nearly empty valence shell will be able to shed and receive electrons. This flow of electrons among atoms is electricity. As we mentioned previously, copper’s nearly empty valence shell allows it to shed and accept electrons, so it is a good conductor of electricity. Neon, with its full valence band, is very nonreactive, so it is resistant to the flow of electricity; in other words, it is an insulator.

Knowing both of these qualities is important to understanding electronics. Electronics relies on our having the ability to control the flow of electricity. We need to be able to slow it, block it, and even modulate it. (More on that later!) This requires that we understand which materials are conductors (highly conductive or low resistance), which are insulators (poor conductors or strong resistance), and which are semiconductors (in between low and strong resistance).

Conductors

Elements that are grouped on the left side of the periodic table have fewer electrons in their valence shell and can serve as good conductors. That’s because these electrons are loosely bound to their nuclei (the plural of nucleus) and can easily be separated from their atom and travel to a positively charged ion. In other words, these elements allow for electricity—which is simply the flow of electrons—to flow easily. Examples of common metals that are relatively good conductive materials are silver (Ag), gold (Au), and copper (Cu), all of which contain just one electron in their valence shell; that lone electron is easily removed when electricity is flowing. Moving to the right from these metals to the far right of the periodic table you encounter more stable elements that are less conductive.

Insulators

Elements that have full or nearly full valence shells either hold on to their existing electrons or attract electrons so that their valence shell becomes full. These elements are insulators that have great resistance and can slow or block the flow of electricity. They don’t have room on their valence shell to accept electrons, and their nearly full outer shell holds tightly to the electrons it already has.

The elements at the far right of the periodic table are called the noble gases. These are extremely good insulators as they are very nonreactive. The naturally occurring noble gases are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn).

Semiconductors

The elements in between the metals and the noble gases on the periodic table are generally semiconductors. Some elements commonly used as semiconductors are silicon (Si) and germanium (Ge). These elements can be combined with others to introduce impurities that can conduct electricity. This process is called doping, and when an element is used in this capacity, it is referred to as a dopant.

Consider an atom of silicon, which has four electrons in its valence shell. When you look at multiple atoms of silicon, as shown in the following figure, you can see that they arrange themselves quite neatly into what is called a crystalline structure, meaning the atoms form a repeating pattern in each direction, with each of its electrons in the valence shell perfectly paired with its neighboring atom.

Now let’s look at what happens when two very different dopants are added. Phosphorus (P) has 15 electrons—2 on its inner shell, 8 on its second shell, and 5 on its valence shell. When it bonds with silicon, the combination yields a loosely attached electron. Because that electron can be easily released, a negative charge can easily flow through the doped semiconductor. Phosphorus acts as a donor impurity, because when it is added to silicon it releases or donates electrons. This yields what is called an n-type semiconductor, where n means negative.

You can create a p-type semiconductor—p meaning positive—by adding boron (B) to silicon. Boron has five electrons, two on its inner shell and three on the valence shell. When you combine these two elements, the bond between the two elements produces a valence shell with seven electrons. This nearly full valent shell does not want to release electrons. However, it does have room to accept an electron in the remaining space, which is referred to as a hole.

FIGURE 1.3 Atoms of silicon in a crystalline structure. Note that the image doesn’t depict all of the atoms on the outside rows; silicon has four electrons in its valence shell.

FIGURE 1.4 An n-type semiconductor formed by doping with phosphorus.

FIGURE 1.5 B dopant with three electrons in the valence shell.

Although the atomic qualities of a material are the most important in determining its conductivity, other factors need to be considered when determining an element’s conductivity:

The physical characteristics of the material: A thick strip of aluminum will conduct more electricity than a thin one. A short wire shortens the distance needed for the current to travel compared to a longer wire.

Temperature: Different materials change in their conductivity depending on the temperature. Metals tend to become less conductive when heated and some become superconductive at extremely low temperatures.

Electron Flow Versus Hole Flow

When an electron leaves an atom, it creates a gap for the next electron to jump into. The electrons move in one direction, so the gaps always open up in the reverse direction.

The movement of the electrons is called electron flow. The opening up of the gaps is called hole flow.

The flow of electrons is like a flow of marbles through a straw. One electron moves into the space created by the movement of the previous electron down the line.

FIGURE 1.6 When electrons move to the empty holes during electron flow, the “movement” of the empty holes is called the hole flow.

The Least You Need to Know

An atom has a nucleus containing positively charged protons and neutrally charged neutrons; the nucleus is surrounded by a cloud of negatively charged electrons.

A stable atom has equal numbers of protons and electrons. When an atom gains or loses an electron, it becomes an ion—a charged atom.

Electrons travel in shells or bands around the nucleus. The outer shell is called the valence shell. When electrons move from one atom to another, they create an electric current.

Materials are classified as conductors, insulators, or semiconductors based on their resistance to conductivity. Semiconductors can be doped to create n-type or p-type semiconductors.

Chapter Review Questions

1.Electrons are ________-charged particles.

2.The outermost shell (or band) of electrons is called the ________ shell/band.

3.A(n) ________ is an atom with a charge.

4.________ is the tendency of a material to resist the flow of electrons.

5.Beyond the atomic structure of a material, name two things that affect the conductivity of a material.

6.True/ False: Silver, gold, and copper all have just one electron in their valence shell, so these metals are generally considered good insulators.

7.N-type semiconductors are doped to allow for the easy movement of a ________ charge.

8.True/ False: Hole flow is in the same direction as electron flow.

9.The naturally occurring noble gases are: (name at least 3) ________, ________, and ________.

10.________ charges repel, while ________ charges are attracted to each other.

CHAPTER 2

HOW ELECTRICITY WORKS

In This Chapter

•Creating paths for electricity to follow

•Giving electricity a push

•Measuring voltage, current, and resistance

•Calculating power using Ohm’s Law and Joule’s Law

Now that you know what electricity is at the most fundamental level, it’s time to find out more about how it flows and how you can take charge of that flow. Electricity needs a path and a push. Once you understand how to manipulate the path and the push, you can control the devices you connect to the path.

Circuits

The path on which electricity flows is called a circuit. Once flow has been established, electric current can travel endlessly through a conductive material if the circuit remains as a loop. Chapter 1 compared the flow of electric current to marbles moving through a looped straw. In this comparison, the circuit is the straw, and it can’t carry electricity if there is a break anywhere along it.

More practically, a circuit is any arrangement that allows for electrical current to flow. An example of a very basic circuit might be a battery connected to a lamp. A computer’s motherboard contains several much more complicated circuits. Electronics is all about analyzing, building, and creating circuits that use electrical current.

FIGURE 2.1 A circuit is like marbles moving through a looped straw.

The circuit’s current provides power for a device or devices. The device that is powered by a circuit is called the load. Wire connects the battery and the load. In the basic circuit of a lamp and a battery, the lamp is the load. This basic circuit consists of a power supply (the battery), a load (the lamp), and the wire.

Electromotive Force or Voltage

How does the flow get started? Electromotive force (you may see it abbreviated as emf in discussions about electricity and represented by the symbol V in equations) is the push that gets the electrons jumping from one atom to another, sending a current of electrical flow along the way. Electromotive force can originate from many sources, including the following:

Chemical reactions, as in a battery

Electromagnetic generators

Photovoltaic cells (solar)

Generators that convert mechanical energy to electrical energy

Friction

Thermoelectrical sources, which use differences in temperature to create electricity

Titans of Electronics

The first practical electrical generator was designed by Michael Faraday in 1831. He discovered that if you rotate a conductive metal wire in a magnetic field, a process called induction (see Chapter 11), you can generate a current. A generator uses mechanical energy to turn the wire, converting mechanical energy into electric energy that can cause current to flow through a circuit.

Some generators are hydroelectric, meaning that they use the flow of water to turn a turbine. Oil and coal can be burned to cause steam, which also turns a turbine to generate electricity. Atomic energy uses the heat released by nuclear fission to create steam to turn a turbine. Even green energy, such as wind power, relies on a turning turbine to create electricity through induction.

Voltage (V), named after Italian scientist Allessandro Volta, is the measurement of emf. It is the measure of the force required to move electricity between two points on a circuit, known as the potential difference (p.d.) between those two points. You cannot measure the voltage at a single point; it is always a measurement across two points. Like speed or length, to measure voltage you need to have two points to show a relationship.

It may seem that we are using a lot of words to represent the same concept and, frankly, we are. Hopefully, using them all in the same sentence will help clarify relationships: Electromotive force (emf), also known as voltage (V), is the potential difference between two points in a circuit; it is symbolized by the letter E (usually presented as ℰ) and is measured in volts.

Current

Because current (I) is all electrons moving through a circuit, we measure it as it moves through a single point. To account for the fact that electrons are incredibly small, a large unit was created to represent a set number of electrons. A coulomb (pronounced KOO-lum) is equal to approximately 6.25 × 1018 electrons. An ampere (pronounced AM-peer and abbreviated as amp or simply A) is defined as a coulomb of current that moves through a point in one second.

Titans of Electronics

French physicist Charles Augustin de Coulomb is the namesake of the coulomb.

The ampere is named after French scientist André-Marie Ampère.

Again, let’s put it all these terms together in a single sentence: Current is the number of electrons that move in a circuit, it is symbolized as I, and is measured in a unit called an ampere (A).

When you consider how small electrons are, you realize that looking at the number of electrons in a coulomb is almost beyond comprehension. Here is how a coulomb’s value (6.25 × 1018) in individual electrons would look written in standard numbers: 6,250,000,000,000,000,000. This number is obviously unwieldy and difficult to work with, which is why it is almost always represented in scientific notation.

If you use scientific notation to express such a large number, it makes it much easier to solve equations with incredibly large or incredibly small numbers. To learn how to express a large number in scientific notation, refer to Appendix C.

Resistance

Resistance is the oppositional force to emf. It might help to think of resistance as the equivalent of friction slowing down a moving object. As current is pushed through a circuit by voltage, it encounters resistance, which reduces the voltage. This is why we measure voltage across different points along the circuit. The resistance of the material that makes up the circuit determines how much the voltage is reduced.

Titans of Electronics

A German provides the name for the unit of measurement this time around, Georg Simon Ohm.

We measure resistance in relationship to voltage and current. An ohm is the level of resistance that allows the one volt of emf to move one ampere across two points on a circuit. The symbol for an ohm is the Greek letter omega, Ω.

Ohm’s Law

You have now learned the three measurements that are a part of the most basic formula in the field of electronics: Ohm’s Law. Ohm’s Law states that the current (I) between two points is directly proportional to the voltage (V) and inversely proportional to the resistance (R). As an equation, it is written I = V/R. If you have any two of the variables, you can solve for the other. For instance, if you have R and I, you can solve for V using this equation: V = R × I. Similarly, if you know the values of V and I, you can solve for R with this equation: R = V/I.

Power

In a direct current circuit, power is the voltage multiplied by current. The unit of measurement for power is the watt (W), named after the Scottish scientist James Watt. One volt pushing one amp of current equals one watt.

You may be more familiar with the term kilowatt (kW) as a unit of power. A kilowatt is 1,000 watts. Your electric bill lists the number of kilowatt hours (kW-h)—the amount of power in total when a kilowatt of power is delivered constantly over an hour—you use each month. The average American home uses about 700kW-h a month. To put this in some context, think of a 50 watt bulb. If you use that bulb for one hour, you have used 50Wh, (watt hours) and if you use it for 20 hours, you will have used 1kW-h because 50Wh × 20 hours equals 1,000Wh or 1k-Wh.

FIGURE 2.2 Ohm’s Law pyramid shows the relationship between voltage, current, and resistance. Note that if you look at any of the segments of the pyramid, the other two values are shown in their mathematical relationship.

Joule’s Law

Ohm’s law shows the relationship between current, voltage, and resistance. If you want to determine power you need to know another foundational law of electricity: Joule’s law. You can use Joule’s law to calculate the amount of power provided by a circuit. Joule’s First Law gives us the following equation:

Power = Voltage × Current or P = V x I

FIGURE 2.3 The four values that can be solved for using Ohm’s and Joule’s law: power, current, voltage, and resistance. In each quarter of the circle, you can see the variables needed and the relevant equation to solve for each value.

Titans of Electronics

Joule’s Law is named after James Prescott Joule, a British physicist and brewer.

You can combine Joule’s Law and Ohm’s Law to solve for voltage, current, resistance, and power.

Putting It All Together