EET 114 Unit 1. Getting Started in Electronics

Unit 1. Getting Started in Electronics

To begin our study of electronics, we'll start to get familiar with some common electrical components, and with some common instruments that technicians use to make measurements. We'll also see that technicians must understand a number of electrical quantities, and they must know what units these quantities are measured in.

First, you should read the following sections of Thomas Floyd's Principles of Electric Circuits (8th edition):

Units of Measurement (Section 1-1)

After reading from the book, work through the e-Lesson below. It reviews the main points of the reading assignment, and also gives some information not found in the reading. Most important of all, it contains Self-Test questions to give you practice using what you've read about.

After completing the e-Lesson, you'll be ready to take Quiz #1, perform Lab #1, and do Homework #1.

Unit 1 e-Lesson

For any topic below with a Self-Test icon (which looks like this ), click the icon to test your understanding of that topic. Self-Tests are for your practice only; no grades are recorded. The questions will appear in a new window. You may wish to resize this window so that you can read the questions more easily; then close the window when you're finished with the questions for that topic.

Electrical and Electronic Components

If you look inside an electronic device such as a computer or a telephone, you'll see a large of number of electrical parts, or components.
These components include resistors, capacitors, inductors, transformers, and semiconductor devices.

Resistors

Resistors are components that limit the amount of electrical current in a circuit. These are probably the most common type of electrical component.
Here is a photograph of a resistor from Sinclair's labs, shown next to a quarter to give you an idea of its size.

Capacitors

Capacitors are components that store electrical charge. Another way of saying this is that they store energy in an electric field. Capacitors are also widely used to block direct current (dc) and pass alternating current (ac).
Here are some photos of capacitors found in Sinclair's labs. First, here are two ceramic capacitors:

The next photgraph shows three plastic-film capacitors:

Finally, here are three electrolytic capacitors:

Inductors

Inductors are components that store energy in a magnetic field (as opposed to an electric field). Inductors are widely used in filters and in many other applications.
Here is a photo of some inductors found in Sinclair's labs.

Transformers

Transformers are components that increase or decrease the voltage in a circuit.
Here are two photos of transformers from our labs.

Semiconductor Devices

The components discussed above are referred to as electrical components. Modern devices such as computers and radios also contain many electronic components. Most electronic components are made of a semiconductor material, such as silicon.
Semiconductor devices includes diodes, transistors, integrated circuits, and several other kinds.

Identifying Components

In this course and later courses you'll use a variety of components. The sooner you learn to recognize components by sight, the better.
If you're studying this e-Lesson in one of Sinclair's electronics labs, go right now to the cabinet containing components and find examples of resistors, capacitors, inductors, transformers, and other components. Use the pictures given above to identify the components.
Then take this self-test quiz to see if you can recognize the different types of components.
Click the Self-Test icon to check your understanding.

Electronic Instruments

Technicians use a variety of instruments to test and troubleshoot circuits. Some common instruments are dc power supplies, function generators, digital multimeters, and oscilloscopes.

DC Power Supply

A dc power supply is an instrument that produces direct-current (dc) voltages and currents.
In Sinclair's labs, dc power supplies are built into the digital-analog trainers that you will use in many of your courses. A digital-analog trainer combines several instruments into one piece of equipment. Here is a photo of the digital-analog trainers found in our labs:
Here is a close-up photo of the controls for the dc power supply contained in the trainer:

Function Generator

A function generator is an instrument that produces alternating-current (ac) voltages and currents.
In Sinclair's labs, a function generator is built into the digital-analog trainer, which was pictured just above. Here is a close-up photo of the controls for the trainer's function generator (click the photo for a larger picture):
Our labs also have standalone function generators such as this Tektronix model CFG250 (click for a larger picture):

Digital Multimeter

A digital multimeter (or DMM) is an instrument used to measure voltage, current, or resistance.
Sinclair's labs are equipped with several types of DMM's, including the Fluke model 8050 shown here:

and the Tektronix model CDM250 shown here:
Shown below is an inexpensive handheld DMM.

Oscilloscope

An oscilloscope is an instrument that is used to display graphs of quickly changing voltages.
Sinclair's labs are equipped with several types of oscilloscopes, including the Tektronix model 2213 shown here:

LCR Meter

An LCR meter is used to measure values of inductance, capacitance, or resistance.
Other names for this meter include impedance meter, Z meter, and inductor-capacitor analyzer.
Sinclair's labs are equipped with several types of LCR meters, including the Global Specialties model 3200 shown here:

and the Tegam model 253 shown here:

Frequency Counter

Another instrument that we'll use later in this course is a frequency counter, which is used to measure frequencies of ac voltages.
Sinclair's labs are equipped with several types of frequency counters, including the Tektronix model CFC250 shown here:

Identifying Instruments

In this course and later courses you'll use a variety of electronic instruments. The sooner you learn to recognize instruments by sight, the better.
If you're studying this e-Lesson in one of Sinclair's electronics labs, go right now to the lab bench and find examples of digital-analog trainers, function generators, multimeters, oscilloscopes, and LCR meters. Use the pictures given above to identify the instruments.
Then take this self-test quiz to see if you can recognize the different types of instruments.

Electrical Quantities (See pages 2 and 3 of Floyd's book for more details.)

Up to this point we have looked at several examples of components and instruments. Those are all physical objects that you can hold in your hand.
A technician must also understand and know how to measure many different electrical quantities. These are concepts, not physical objects. Common examples of electrical quantities are voltage, resistance, and current.
We use italic letters as symbols to represent electrical quantities. For example:

V is the symbol for voltage;
R is the symbol for resistance;
I is the symbol for current. Why I instead of C? Because C is used as the symbol for another electrical quantity, and we wouldn't want to use the same symbol to represent two different quantities.

Electrical Units (Floyd, pages 2-3)

Each electrical quantity has a unit in which it is measured.
- For example, current is measured in amperes, or, to say the same thing in another way, the ampere is the unit of measure for current. A particular current might have a value of 5 amperes.
- Here's an everyday, non-electrical example of this idea of units. Think about the quantity called weight. Weight is measured in pounds, or, to say the same thing in another way, the pound is the unit of measure for weight.
Just as we have a symbol to represent each electrical quantity, we also have a symbol to represent each electrical unit. Usually the symbols for units are plain, non-italicized letters.

For instance, the symbol for the ampere is A. So to show that a particular current is equal to 5 amperes, we would write I = 5 A.

Table of Electrical Quantities and Units (Floyd, pages 2 and 3)

The tables on pages 2 and 3 in the textbook list some important electrical quantities, along with their units and the corresponding symbols. We won't use all of these in this course. The table below shows the ones that I'll expect you to learn:

Quantity	Symbol	Unit	Symbol for the Unit
capacitance	C	farad	F
charge	Q	coulomb	C
conductance	G	siemens	S
current	I	ampere	A
energy	W	joule	J
frequency	f	hertz	Hz
impedance	Z	ohm	Ω
inductance	L	henry	H
period	T	second	s
power	P	watt	W
reactance	X	ohm	Ω
resistance	R	ohm	Ω
time	t	second	s
voltage	V	volt	V

If you look closely, you will notice that the symbols for most quantities are written with italicized letters, such as I or V. But the symbols for most units are written with plain, non-italicized letters, such as A or V. This is the standard, accepted way of doing things. Our textbook follows this rule, and you should too when you use these symbols in a typed paper or lab report.
The symbols for some quantities and some units are letters from the Greek alphabet. The only example in the table above is the symbol Ω.

Electrical-Units Matching Game

By the end of this course you'll need to memorize which units go with which quantities.

I know it takes a while to memorize things like this, so don't panic! You'll have plenty of time before anyone expects you to remember all of these terms and symbols. But the sooner you start learning the language that technicians and engineers use to communicate with each other, the better off you'll be.
For this week's lab, the three rows of the table that you'll want to remember are the rows for capacitance, inductance, and resistance.

To work on this skill, be sure to play the Electrical-Units Matching Game. Like all of the games on the Games page, this one has a Study mode that reviews the theory, a Practice mode that lets you practice with no time pressure, and a Challenge mode that tests your skill while the clock is running. If you're fast, you may even get your name on the high-score board!
The game will teach you a few more units that aren't listed in the table above. You won't need to learn those for this course, but you'll use them in later courses.

Electrical-Symbols Matching Game

You also need to memorize the symbols for the different quantities and units. To learn these, play the Electrical-Symbols Matching Game.
Again, I don't expect you to learn all of these terms and symbols immediately. Come back to these games throughout the quarter to keep practicing.

Relating Components to Quantities

Let's take a closer look at three of the components mentioned earlier (resistors, capacitors, and inductors), and see how these components relate to some of the quantities we've just been discussing.

More About Resistors

Earlier we said that resistors are components that limit the amount of electrical current in a circuit, and we showed this photograph of a resistor:
Now we can add to our earlier definition by noting that every resistor is manufactured to have a specific amount of the electrical quantity called resistance.
Recall from the table above that the symbol for resistance is R, and that resistance is measured in ohms, and that the symbol for ohms is Ω. We'll use these symbols frequently when discussing resistors.
- For example, suppose that a particular resistor has a resistance value of 200 ohms. We would write this as:
  R = 200 Ω
Typical resistance values for resistors range from 10 Ω (a small resistance) to 10,000,000 Ω (a large resistance).
In the photo above, note the colored bands on the resistor's body. These colors indicate the resistor's value in ohms. We'll learn how to "read" these colors in Unit 2 of this course. (If you want to get a head start on this topic, a good way to do it would be to read the "Study" section of the Color-Code Matching Game and then play the game until you can remember which number each color stands for.)

More About Capacitors

Earlier we said that capacitors are components that store electrical charge, and we showed several photos of capacitors, including this one:
Now we can add to our earlier definition by noting that every capacitor is manufactured to have a specific amount of the electrical quantity called capacitance.
From the table above we see that the symbol for capacitance is C, and that capacitance is measured in farads, and that the symbol for farads is F. We'll use these symbols frequently when discussing capacitors.
- For example, suppose that a particular capacitor has a capacitance value of 1 farad. We would write this as:
  C = 1 F
Typical capacitance values for capacitors range from 0.0000000001 F (a small capacitance) to 0.001 F (a large capacitance).
In the photo above, note the numbers on the larger capacitor's body. These numbers indicate the capacitor's value in farads. We'll learn how to interpret these numbers in Unit 2.

More About Inductors

Earlier we said that inductors are components that store energy in a magnetic field, and we showed this photograph of some inductors:
Now we can add to our earlier definition by noting that every inductor is manufactured to have a specific amount of the electrical quantity called inductance.
Our table of quantities tells us that the symbol for inductance is L, and that inductance is measured in henries, and that the symbol for henries is H. We'll use these symbols frequently when discussing inductors.
- For example, suppose that a particular inductor has an inductance value of 1 henry. We would write this as:
  L = 1 H
Typical inductance values for inductors range from 0.0000001 H (a small inductance) to 1 H (a large inductance).
In the photo above, note the numbers on the left-hand inductor's body. These numbers indicate the inductor's value in henries. We'll learn how to interpret these numbers in Unit 2.

Prefixes for Large or Small Numbers

When discussing resistances, capacitances, inductances, and other electrical quantities, we must often deal with very large numbers (in the thousands or millions, or even larger) and with very small numbers (thousandths or millionths, or even smaller).
To avoid having to write lots of zeroes when dealing with large or small numbers, we'll use some standard prefix letters as abbreviations.
- For example, we know that resistance is measured in units called ohms (abbreviated Ω). But many resistances have values in the thousands of ohms or millions of ohms, and for such large values it's convenient to use larger units called kilohms (abbreviated kΩ) or megohms (abbreviated MΩ).
- Also, we know that capacitance is measured in units called farads (abbreviated F). But many capacitances have values much smaller than one farad, and for such small values it's convenient to use smaller units called picofarads (abbreviated pF) or nanofarads (abbreviated nF) or microfarads (abbreviated µF).
- Likewise, inductance is measured in units called henries (abbreviated H). But since many inductances have values much smaller than one henry, it's often convenient to use smaller units called microhenries (abbreviated µH) or millihenries (abbreviated mH).
In Unit 2 we'll discuss the prefixes k, M, p, n, µ, and m in more detail. We'll see, for instance, that 1 MΩ is just a shorthand way of writing 1,000,000 Ω, and that 1 µF is just a shorthand way of writing 0.000001 F. For now, you should simply be aware that an expression such as

C = 330 pF
is a shorthand way of writing a very large or very small number without having to write a lot of zeroes.

Nominal Values and Tolerances

Suppose you're building an electronics project that requires a 220 Ω resistor. (Remember, this means a resistor whose resistance is equal to 220 ohms.) So you go to the nearest Radio Shack store and ask the clerk for a resistor of that size. The clerk will be happy to sell you such a resistor, but will the resistor's value be exactly 220 Ω? Probably not. It will probably be a little higher (maybe 224 Ω) or a little lower (maybe 213 Ω), but it will be close enough to 220 Ω that your project should work correctly when you build it.
In this example we would say that 220 Ω is the resistor's nominal value, which means the value that the manufacturer was shooting for when they manufactured that resistor. But the resistor's actual value will probably be somewhat higher or lower than the nominal value.
How far away from the nominal value can the actual value be? To quantify this, manufacturers use tolerance ratings. When you buy that resistor at Radio Shack, you might have your choice of buying a resistor with a 5% tolerance, or one with a 10% tolerance, or one with a 20% tolerance. This tolerance rating tells you how far from the nominal value the actual value may be.
- So if you buy one with a 5% tolerance rating, then the manufacturer is guaranteeing you that the resistor's actual value will be within 5% of 220 Ω.
The same ideas apply to other components as well. If you buy a 470 pF capacitor or a 15 mH inductor, those numbers represent the nominal values of the components. The actual values will probably be higher or lower, but the tolerance ratings will tell you how close to the nominal values you can expect the actual values to be.

Percentages

Tolerance ratings are almost always given as percentages, such as 5% or 10%. You've probably studied percentages at some time in a math class, but let's do a quick review.
The main thing to remember about percentages is that they just involve moving a number's decimal point over by two places.

Example: writing 5% is just a fancy way of writing the number 0.05. So, to use an example involving money, if somebody asks you to find 5% of $750, the answer is $37.50, since
0.05 × $750 = $37.50

Your calculator may have a % key, in which case you could solve that problem by typing in
5% × 750 =
but when you type that in, your calculator simply changes 5% to 0.05 and then does the multiplication.

Tolerance Calculations

Now let's talk more about the math involved in tolerance ratings. In particular, if you know a component's nominal value and its tolerance rating, then you should be able to figure out the range of actual values that the component might have.
We'll use a 220 Ω resistor with 5% tolerance as an example.
To find a resistor's tolerance in ohms, multiply its nominal value by the percentage tolerance.
- Example: For a 220 Ω resistor with 5% tolerance, the tolerance in ohms is 11 Ω, since
  .05 × 220 Ω = 11 Ω.
To find the minimum value that the resistor can have, subtract its tolerance in ohms from its nominal value.
- In the example above, the minimum possible value is 209 Ω, since
  220 Ω – 11 Ω = 209 Ω.
To find the maximum value that the resistor can have, add its tolerance in ohms to its nominal value.
- In the example above, the maximum possible value is 231 Ω, since
  220 Ω + 11 Ω = 231 Ω.
Therefore, if you buy a 220 Ω resistor with a 5% tolerance rating, the manufacturer is guaranteeing you that the resistor's actual value will be between 209 Ω and 231 Ω.

Unit 1 Review

This e-Lesson has covered some important topics, including:
- some common electronic components
- some common electronic instruments
- a list of electrical quantities, along with their units of measurement and symbols
- resistors, capacitors, and inductors
- some prefixes for large and small numbers (M, k, m, µ, n, p)
- tolerance calculations.
To finish the e-Lesson, take this self-test to check your understanding of these topics.

Congratulations! You've completed the e-Lesson for this unit. What's next?

Take the Practice Quiz to see how the quiz tool works, and then take Quiz #1.
Perform Lab #1.
Do Homework #1.
Keep practicing your skills by playing the games on the Games page.

Then you'll be ready to go on to Unit 2's e-Lesson.

Nick Reeder | Electronics Engineering Technology | Sinclair Community College

Send comments to nick.reeder@sinclair.edu