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1.  INTRODUCTION

You are at the best, free online "Basic Electronics Course". Just read the brief blocks of text, view the videos, and check out some of the screened internet links. This is the easiest, fastest way to learn basic electronics. No sign-up requirements and it is free. The menu table above provides easy access to many interesting electronics topics. Take your time and enjoy.

Everyone today is exposed to electronic devices in one way or another.  The computer revolution is a good example.  Everyone can benefit from additional knowledge of electronics.  Even a quick scanning of this page will help.  A study of electronics starts with electricity, magnetism and basic electronics.  This includes Ohm's law and other basic principles of electricity.  Obtain and study various books on electronics - this is really a must as each author will explain things in a little different way to help you grasp the concepts.  

All the internet links to other web sites found on 101science.com were screened to provide you with the BEST the internet has to offer on each subject.  This will save you many hours of searching for good educational material.  This site is for everyone from the beginner to expert electrical engineering professional.  There is something here for every level of expertise in the world of electronics.  If you just need information on one specific area, use the table above to navigate to the information you need.  If you need more instruction - read on.

Maybe you already know some basic electronics and want to test yourself to see exactly how much you do know.

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2.  BASIC ELECTRICITY

ELECTRICITY AND MAGNETISM BASICS - It all starts with the electrons moving around atoms. Electricity is the movement of electrical charge from one place to another.  Electric charges do not exist without their associated electric and magnetic fields. This module will introduce you to many of the basic concepts involved with electricity and magnetism.  

MATTER - Matter is physically everything that exists that we can touch and feel.  Matter consists of atoms. Now we will introduce you to the structure of atoms, talk about electrons and static charge, moving charges, voltage, resistance, and current. You  will learn about the properties of magnets and how magnets are used to produce electric current and vice versa. All matter can be classified as being either a pure substance or a mixture.  Matter can exist as either a solid, liquid, or a gas and can change among these three states of matter.  In electronics the most important matter are conductive metals, and non-conductive insulators. In Quantum Field Theory (QFT) you will learn that everything may very well be a field/wave but that is another story for much later in our learning process. Here we will stick to thinking in classical physics terms.

ELECTRICAL CHARGE - Any object or particle is or can become electrically charged.  Nobody completely understands what this charge consists of but we do know a lot about how it reacts and behaves.  The smallest known charge of electricity is the charge associated with an electron.  This charge has been called a "negative" charge.  An atoms nucleus has a positive charge.  These two un-like charges attract one another.  Like charges oppose one another.  If you had 6,250,000,000,000,000,000 electrons in a box you would have what has been named; one coulomb of charge.  An easier way of thinking about a large number like that is called "powers of ten" and it would look like this 6.25 x 10^¹⁸ electrons.  It is simply a way to let you know to move the decimal point to the right 18 places.  When electrical charges are at rest, meaning they are not moving, we call that static electricity.  If charges are in motion we then have a flow of charge called electrical current.  We have given the force that causes this current a name called electromotive force and it is measured by a unit called a volt (V).  The unit of measurement of the current (I) or movement of the charge is called an ampere.  The resistance, or opposition, to current flow is called an ohm (R).

ELECTRICAL FIELDS- Around a charge is an electric field.  With every electric field there is a magnetic field.  While we can't see these fields, or yet know exactly what they consist of, we can measure them with instruments and tell a great deal about their behavior.  We can then use this knowledge to our benefit.  The design and construction of electric motors, computers, radios, televisions, stereos, and many other electrical and electronic devices depend upon a knowledge of these basic principles of electricity.  As you can see we have given names to these phenomenon to make it easier for us to study and use.  We could have called them Dick, Jane and Mary but instead we named them for the scientists that discovered or first studied them; Volt, Ampere, and Ohm.  Mr. Volt, Mr. Ampere, and Mr. Ohm spent many years of their lives studying electricity.  They were not alone however as many other scientist were studying and learning more about electricity as well.

WATTS - POWER - What is a watt?  A watt is the International System unit of power equal to one joule per second.  The symbol used for a watt is "P" for power.  Power in watts is found by multiplying a circuits current (I) times its voltage (V).   You will learn more about power in watts in the ohms law section below.  

P - I*V 

If you don't have a clue as to what electrical current and voltage are - read on.  We will cover that shortly.

Moving electric charges are the heart of basic electronics.  Knowing what moving charges are and how various electronic components affect the moving charges is the foundation of basic electronics.  View the videos and continue on down the page.  These are the basic building blocks of understanding "Basic Electronics". 

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3.  BASIC ELECTRONICS

Now that you have a general background in electricity and moving charges you can move on to learning more about basic electronics.  Electronics puts a knowledge of electricity to useful work.  Electronics applies electrical current flow of electrical charges to circuits to accomplish specific tasks.  Amplifiers can be constructed from glass "tubes" containing metal elements, or more commonly today with solid state diodes, transistors, or integrated circuits.   An amplifier is simply a device or circuit that takes a small signal input and controls a larger current as it output.  The input signal voltage is small and the output voltage is larger - amplified.  A circuit containing wire conductors, resistors, capacitors, inductors and amplifiers can be configured in many ways to build various electronic circuits like oscillators, digital logic circuits, computer circuits, television and video circuits and much more.  An oscillator by the way is just an amplifier with some of the output fed back into the input.  Sounds like a perpetual motion machine but it isn't as the amplifiers power supply is providing the additional energy that is lost in the circuit and keeps the circulation, i.e. oscillations going.

Basic electronics is all about electrical components and the circuits consisting of those components .  Common components are resistors, capacitors, inductors, transistors, and integrated circuits.  You will find each of these components described in detail in the following numbered sections.  The components are interconnect with conductors, either physical wires or printed circuits.  The components make up linear analog amplifiers, oscillators, and filters as examples.  They also can be configured to create digital logic circuits such as memories, gates, arithmetic units, and central processing units.  So you will find basic electronics in every computer, mp3 player, radio, TV and may other appliances in your home, car, or on your body.  Each circuit has a job. Components are interconnected to perform a specific task.  First learn about each individual component and how it works then learn about how to interconnect them to make useful end products. Continue your study by reading the numbered sections to follow.

Get the Malvino books below if you need an easy to read but excellent book to learn electronics as a technician.

Malvino Electronic Principles

Instructor's Manual for Malvino...  

Experiments for Electronic Principles... 

There is another method of learning basic electronics.
It is hands-on by doing simple projects.
You will need some electronic parts avaialbe from a good junk box.

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4. RESISTANCE - 

RESISTORS AND RESISTOR CIRCUITS - Resistance is the opposition to current flow in various degrees.  The practical unit of resistance is called the ohm.  A resistor on one ohm is physically very large but provides only a small resistance to current flow. A resistor of one million ohm's is physically small but presents a high resistance to current flow. A resistance that develops 0.24 calorie of heat when one ampere of current flows through it for one second has one ohm of resistance.  The unit of resistance is often represented by the Greek letter omega.  Resistors are often made of thin layers of carbon or lengths of small copper wire.  They can also be thin deposited layers of metallic material.  An image of a few resistor types is shown below.

What is electrical current? Electrical current, represented by the letter "I" in formulas, and it is the flow or rate of electric charge. This flowing electric charge is typically carried by moving electrons in a metallic conductor or electronic components such as resistors or transistors as an example. The unit of electrical current is the ampere, named after a french mathematician, Andre Marie Ampere. What is electrical voltage?  Electrical voltage is represented by the letter "V" in formulas and it is the electrical pressure a moving charge is under.  In the case of a static charge, one that is not moving, then voltage is the potential difference or pressure of the charge.  The relationship between current (I), resistance (R), and voltage (V) is represented by the formulas developed in Ohm's law.  We will study that in section 5 below.

RESISTORS AND RESISTOR CIRCUITS- 

Resistors can be connected in series (end to end), or in parallel (across one another), or in a combination of series and parallel.   If you connect two, 1/4 watt, 100 ohm resistors across one another (i.e. in parallel) then the total resistance in ohms is one half of one of the resistors.  In this example the resistance would be 50 ohms.  The wattage doubles as the current is now split between the two resistors.  The combination can now handle up to one half a watt safely.  If the two resistors were connected end-to-end (i.e. in series) the resistances add and in this case would be 200 ohms.  The wattage in this series case stays the same, 1/4 watt.  This information is handy to know as it is easy to calculate in your head and will allow you to devise additional resister values from a limited resistor bench stock. Resistor color code calculator.

 

RESISTORS IN SERIES: Connecting resistors in a string one pigtail to another is called connecting them in series.  When connected this way the resistance of one resistor adds to the next in line.  For example a 100 ohm resistor in series with a 500 ohm resistor is the same as having a 600 ohm resistor.  The wattage capability stays the same, in other words if the resistors are all 1/4 watt the string is 1/4 watt.  

Resistance in series resistance simply adds:   R = R1 + R2. This can be extended for more resistors: R = R1 + R2 + R3 + R4 + ...  

RESISTORS IN PARALLEL:  When resistors are connected in parallel (parallel; meaning they are tied across one another) their combined resistance is less than any of the individual resistances. There is a special equation for the combined resistance of two resistors R1 and R2:

Combined resistance of two resistors in parallel:   R =  R1 × R2  R1 + R2

For more than two resistors connected in parallel a more difficult equation must be used. This adds up the reciprocal ("one over") of each resistance to give the reciprocal of the combined resistance, R:

1    =    1  +  1  +  1  + ... R R1 R2 R3

The simpler equation for two resistors in parallel is much easier to use!

Note that the combined resistance in parallel will always be less than any of the individual resistances.

Resistor values are measured in ohms.  A thousand ohms is written as 1k to eliminate all the zeros.  The k represents three zeros.  A million ohms is represented by 1M.  Therefore; 1000 ohms = 1k ohm and 1000k ohms = 1M ohm.  Since resistors are so small their value is marked by a color code.  

 

RESISTOR COLOR CODES -  Resistors use color coded stripes to indicate their value in ohms. 0=Black, 1=Brown, 2=Red, 3=Orange, 4=Yellow, 5=Green, 6=Blue, 7=Purple, 8=Gray, 9=White.    

Video showing resistor color codes.

 

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5. OHMS LAW  

Ohm's Law is extremely important in learning basic electronics.

What is Ohm's Law?  Ohm's Law is a formula that describes the relationship between resistance, current and voltage in an electrical circuit.  The formula is R (resistance in ohms) = (equals) V (voltage in volts) divided by I (current in amperes). 

That is:  R = V ÷ I

...and algebraic rules tells us that I - V ÷ R and V = I*R.

    I = V ÷ R, V = I*R, R = V ÷ I, and P (power in watts) = I*V are the fundamental formulas of Ohm's law.  (The * means to multiply the two quantities together).  Where V is the circuit voltage in volts, I is the circuits amperage in amps, and R is the resistance in ohms.    

Almost every electrical and electronic circuit involves resistance, current and voltage.  This is why it is vital you understand the relationships between them. 

As an experiment you can set up a circuit by connecting  resistors in series with a battery, measure the voltage across the resistors with a voltmeter, measure the current in the circuit by placing an ammeter in series with the resistors and the battery.  If you know the voltages and current in the circuit you can use Ohms law to calculate the resistance.  With the resistor out of the circuit you can measure it's resistance directly with an ohm meter.  The multi-meters today can measure ohms, volts and amperes (usually measured in miliamperes in practical circuits)  all in one piece of test equipment.

Below is a graphic chart showing the various relationships between resistance, current, voltage, and power and shows how one unknown can be calculated if you know the other two.

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6. CAPACITORS - 

A capacitor  is a device that stores an electrical charge when a potential difference (voltage) exists between two conductors which are usually two plates separated by a dielectric material (an insulating material like air, paper, or special chemicals between two sheets of aluminum foil).  Capacitors block DC voltages and pass AC voltages.  They are used as filters, AC coupling capacitors and as by-pass capacitors.  They are also used in conjunction with resistors and inductors to form tuned circuits and timing circuits.  A capacitors value C (in Farads) is dependent upon the ratio of the charge Q (in Coulombs) divided by the V (in volts).   Common capacitors come in values of microfarads or Pico farads.  Often you will have to convert between Pico farads and micro farads.  A chart is provided below to assist in the conversion.  For a list of capacitor terms defined: Click HERE.   Measuring capacitance requires a capacitance meter.  This is separate piece of test equipment.  There are attachments for multimeters that allow measurement of capacitance directly. Also read this tutorial on how to test capacitors.

CAPACITOR Value Conversions:

Some capacitors may be marked in micro farads and others of the same capacitance value marked in Pico farads.  One Pico farad equals one micro-micro farad.  You may need to make conversions between the two equivalents.

Prefix	Power of  10	Example
Mili	10^-3	.001
Micro	10^-6	.000001
Nano	10^-9	.000000001
Pico	10^-12	.000000000001

1 micro F	=	1000000 uuf
1 uuf	=	1 pf
.01 uf	=	10000 pf
.005 uf	=	5000 pf
.009 uf	=	9000 pf
.0001 uf	=	100 pf
.0005 uf	=	500 pf
.0009 uf	=	900 pf

A capacitor marked 104M is a .001 uf +- 20%

A capacitor marked 103M is a .01 uf +- 20%

A capacitor marked 102M is a .1 uf +- 20%

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Now continue below with your free "basic electronics" learning process.
Yes, it is that easy!

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7. INDUCTORS  -  

Inductors  are usually made with coils of wire.  The wire coils are wound around iron cores, ferrite cores, or other materials except in the case of an air core inductor where there is no core other than air.   The inductor stores electrical charge in magnetic fields.  When the magnetic field collapses it induces an electrical charge back into the wire.  Inductors are associated with circuit capacitance and can form a tuned circuit and resonate at a particular frequency.   Two coils close to one another, as they are in a transformer, literally transfer charge from one coil to the other.  This is called mutual inductance. 

Inductor Calculators:

Inductance Calculator
Circuit Sage: Inductor Tools and Links
The Engineers' Club Online Service - Engineering Calculators

TOROIDS

FERRITE CORE TOROIDS - a special type of inductor  

Today you must learn about powdered iron cores and ferrite materials for winding your own toroidal coils.  Click here for basic background information on powdered iron and ferrite materials.  You will need to know the formulas for calculating toroidal core inductors; click HERE for FORMULAS. The cores will be made from different materials.  You will also need information on powdered iron material.  Now you have all the information you need to wind toroidal coils for your electronics projects. For core material table: https://www.amidoncorp.com/pages/specifications 

  To calculate the approximate inductance of a toroid, use the JAVA calculator found here:  http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/indtor.html#c1 Courtesy of Carl R. (Rod) Nave, Georgia State University.  Be sure to visit their main site loaded with JAVA calculators and other science information at: HyperPhysics http://hyperphysics.phy-astr.gsu.edu/hbase/hph.html  including an offer of a  CD containing of all their fine materials.

Toroid Approximate Inductance CALCULATOR - Toroid CALCULATOR

Torroid Inductance charts: http://www.electronics-tutorials.com/basics/toroidcharts_mcq.htm

http://home.sandiego.edu/~ekim/otherjunk/inductor.pdf

Testing Unknown Ferrite Cores

Ferrites are roughly divided into two groups. Those with permeabilities up to 850 are usually made from nickel-zinc material and have high volume resistivity ranging from 1x105 to 1x108. Higher permeability ferrites are usually made from manganese-zinc material and have volume resistivity ranging from 0.1x102 to 1x102. Iron powder cores are usually color coded and have very high volume resistivity. An initial test of the material can be made by checking the dc resistance between opposite faces/sides of a core. Low readings indicate a high permeability material. If you can measure inductance at a low frequency (10-100kHz), wind 10 turns of wire on the core and measure the inductance. You can then work back from the ferrite material formula and calculate the AL value, which can be compared with the tables of known cores of the same physical dimensions and so come up with a reasonable match. If 10 turns does not give a measurable reading try 20 or 30 turns.  

RF power rating can be roughly checked by using two exactly similar cores each wound with the same primary and secondary turns (say 10 turns each on primary and secondary) and then connecting the cores back to back as shown. This arrangement provides a 1:1 equivalent so that the transmitter sees the correct load. Losses are doubled by using two transformers, but this does not matter for the test. Set the transmitter to the desired frequency and reduce the rf power output to a minimum. Increase the power output in small steps (say 5 -10W per step) holding each setting for 30 seconds then checking the temperature of each transformer. The transformers should only get warm to touch but NEVER hot. When the final temperature of each transformer has reached about 40 deg.C you can say that you have reached the power limit for that particular core. Some cores will get hot at very low power. You have to make a value judgment about the core physical size versus the power rating achieved.

Ferrite (software program) is used to calculate the number of turns required on toroidal ferrite cores to achieve the desired millihenry-value inductance. 15 different ferrite toroids are included in this application. This program will calculate the winding data for an inductance range of 0.001 to 27 millihenries.
Style: CONSOLE , File size: 64K , zipped 31K.
Bug Fixes: Thanks to PA3CKR for the bug report ; fixed Jan 19/99.
Current Version is 1/19/99
Download the ferrite.zip file

RESONANT CIRCUITS - a combination of capacitance, inductance and resistance.

Tuned circuits are found within electronic circuits where, for example, only one certain frequency is of interest.  The filtering action of a tuned circuit is often associated with amplifiers as is found in a radios intermediate frequency stage.  Only one frequency is amplified due to the filtering action of the tuned circuit.  Tuned circuits may be designed for a very a narrow band of frequencies or with a wide bandwidth.  Tuned circuits are also found in oscillators.  Here the tuned circuit allows oscillations only at the tuned circuits resonant frequency in a properly designed circuit. Resonant circuits are a combination of inductance, capacitance and resistance. Please look at some of the links below for more detailed study of resonant circuits..

Links to other interesting web site about toroids and other inductors.

Useful hints concerning winding toroid coils.
Building a toroid http://www.hamradio-online.com/1999/apr/w6bky-10.html
Toroid Inductance Charts http://www.electronics-tutorials.com/basics/toroidcharts_mcq.htm
A GREAT Inductor Impedance CALCULATOR online - http://www.cvs1.uklinux.net/cgi-bin/calculators/ind_imp.cgi

• Introduction - Use of Ferromagnetic Cores
• Choice of core material - choice of material is of prime importance
• What size toroid core? - Design examples are given
• Using the data tables
• Winding hints
• Line filters and chokes
• Switched mode supplies
• Variable coil forms
• Suppression beads
• Bobbin core
• Balun cores
• Core cross references
• Downloads
• RFI suggestions
• Magnetic formula
• Australian resellers
• Price lists
• Ordering information
• Links

A Video Demonstrating a Resonant Circuit

RF Simulation Freeware - RFSim99

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8. Math for Electronics

Do you need math skills to understand electronics?  Yes!  All science subjects including electronics (a division of physics) require various levels of understanding mathematics.  If you are interested in electronics only as a hobby then general math may be all you will need, to get by.  If you are serious about becoming an electronic technician then you will need at least a basic understanding of algebra and and be able to use and make graphs.  Electrical engineers need advanced mathematics training through calculus. 

Why, you may ask?  Basic electronics involves the use of equations.  For example, Ohms law requires a basic knowledge of algebra to fully understand it and to be able to use it effectively.  Electronic technicians will use Ohms law and other algebraic formulas frequently in typical day's work.  Some knowledge of trigonometry would be helpful.  Electrical engineers need to know how to calculate various rates of change in electrical parameters in a quick and relatively simple manner.  Without the appropriate skills at your level of interest you will be greatly handicapped in your work.  There are substitutes for many situations such as pre-printed charts, databases, cookbook circuits, and internet resources.  But they may not quite serve your current purpose and will take time to research and find.  It is best to obtain basic math skills to a level required by your specific work.

• Learn algebra here.
• Learn about graphs here.
• Learn about graphs of a line here.
  Learn about graphing a function here.
• Learn more about domain and range here.
• Learn about geometry HERE.
• Learn about statistics for electronics HERE
• Learn about trigonometry here.
• Learn calculus here.  (Don't miss this - click)
• Learn about using MathCad for electronics problems.
• See our mathematics section for more math links.

Scared of calculus? Scared of calculus symbols?  No need to be as they are not meant to scare you.  They are really very simple once you know how to think about them and know what they represent.  For example, often you will see the symbol d or perhaps dx in a formula.  Well, d simply means a small amount of something. So, dx simply means a small amount of whatever x represents.  Don't try to multiply the two (d and x), they are not meant for that, just think of dx as a small amount of x, period.   The symbol dx is called a differential.  Also, you might have seen this symbol, called an integral.   Now that is scary, right?  No, not any more because now you know it is simply a tall skinny S.  Now how can a tall skinny S scare anyone?  If you think of as meaning "the sum of" (the word sum starts with an S) well,  that isn't scary either.  You know that 4 is the sum of 2 + 2 already.  Let's say you wanted to add up all the little bits of x and determine the sum of all the dx's you have.  Now putting these two symbols together,dx simply represents "the sum of",  all the "little bits of x" that you have.  This process is often called integration, which is simply the assembling together of a lot of little things.  Integral calculus involves adding up little bits of things.  A better definition might be, "the part of calculus that deals with integration and its application in the solution of differential equations and in determining areas or volumes etc."  For more information and explanation of the definitions of integral and differential calculus see this page - HERE - and more HERE.

So how does calculus help us in electronics?  The whole purpose of calculus is to make very difficult calculations easier.  Yes, sometimes down right easy or usually at least somewhat easier.  Most people think calculus is designed to make simple calculations difficult to impossible.  But that is only because they really don't speak or understand calculus.  It is sort of a foreign language.  Learn to understand the language like we did above and calculus gets a lot easier.  One example is calculating a transformer rate of change in output voltage at any one given instant.  A much easier problem to solve if you use calculus.  Who dreamed this calculus stuff up any way?  If you want to read about the history of calculus go HERE.  If you want another clear explanation of calculus read this - HERE.