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SECUTEL
Basic Electronics Manual
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Table of Contents
Purpose of this module.................................................................................................................... 3
1.
2.
Just What Is Electricity? ............................................................................................................. 3
3.
Terminology of Basic Electronics ............................................................................................... 5
4.
Types of Electronic Components .............................................................................................. 12
5.
Resistors .................................................................................................................................... 13
6.
Capacitors ................................................................................................................................. 16
7.
Light Emitting Diode (LED) ..................................................................................................... 18
8.
Diodes ....................................................................................................................................... 19
9.
Transistors ................................................................................................................................. 21
10.
11.
Inductors/Coils ...................................................................................................................... 24
Integrated Circuit (IC) ....................................................................................................... 26
12.
Circuit Breaker ...................................................................................................................... 28
13.
Fuses ..................................................................................................................................... 29
14.
Switch ................................................................................................................................... 30
15.
Transformer ........................................................................................................................... 31
16.
Electrical Wires & Power Cables .......................................................................................... 32
17.
Battery ................................................................................................................................... 33
18.
Relays.................................................................................................................................... 34
19.
Electric motor........................................................................................................................ 35
20.
Amplifier ............................................................................................................................... 36
21.
Understanding circuit diagrams ............................................................................................ 37
22.
Electronics Formulas You Should Know .............................................................................. 54
23.
The Sixth Sense of Electronics ............................................................................................. 58
24.
Two most important tools to use with Electricity. ................................................................. 59
25.
Conclusion ............................................................................................................................ 60
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1. Purpose of this module
This comprehensive manual helps you in learning and dealing professionally with electronic
components and electronic device maintenance.
What is it?
What does it do?
How can it be tested and utilized?
What is its symbol and units of measurement?
In this manual, we will identify the most important basic electronic components in general
and review their functions, symbols, unit of measurement and examples of their use.
2. Just What Is Electricity?
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Like most things in life, electricity is more complex than you may think. A lot of conditions
must come together to make that little spark when you touch a doorknob or provide the power
to run a supercomputer. To understand how electricity works, this manual helps to break it
down into its parts.
First, you take an electron.
Electrons are one of the building blocks of nature. Electrons are best friends with another of
nature’s building blocks, protons. Electrons and protons are very small and are contained in,
well, everything. A speck of dust contains millions and millions of electrons and protons, so
you can imagine how many there are that make up you.
Electrons and protons have equal and opposite electric charges, with electrons having the
negative charge and protons the positive. Opposite charges are attracted to each other. You
can visualize a similar type of attraction by putting the ends of two magnets together. If the
ends of the magnets are opposite poles, the magnets cozy right up to each other and stick
together.
If the ends of the magnets are the same pole, the magnets will move apart. In a similar way,
because electrons and protons have opposite charges, they are attracted to each other just as
you can see opposite magnetic poles attracting. The attraction between electrons and protons
acts like glue on a microscopic scale, holding matter together.
Although protons stay reasonably static, electrons are adventurous little guys who don’t like
to just sit around at home. They can, and often do, move from one object to another. Walk
across a carpet on a dry day and touch a door handle, electrons traveling between your finger
and the door handle which cause the spark that you feel and sometimes see. Lightning is
another example of electrons traveling between two things — in this case, between a cloud
and the ground. These examples both show electricity in an unharnessed state.
What do electrons use to travel from one place to another? The answer to that question gives
you the next piece of the electricity puzzle, electrons use something called a conductor.
Electricity is simply the movement of electrons through a conductor.
A lot of materials can act as conductors, but some are much better at it than others. Electrons
can move more easily through metal than through plastic. In plastic, even though all the
electrons are moving around their proton buddies, they pretty much stay in their own
backyard. But in metal, the electrons are free to move all over the place. Free electrons in
metal act like marbles thrown on an ice. The electrons glide through the metal like the
marbles slide across the ice. Plastic, an insulator, is more like sand. Marbles don’t go much of
anywhere if you throw them into a sandbox, and neither do electrons in an insulator.
So which materials are good conductors, and which are good insulators? Most use copper and
aluminum as conductors. In fact, electronics projects often use copper wire conductors.
Plastic and glass are commonly used insulators.
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Resistance is the measurement of the ability of electrons to move through a material. A
copper wire with a large diameter has lower resistance to the flow of electrons than a copper
wire with a small diameter. You need to understand resistance because almost every
electronics project you do involves a resistor.
Resistors have controlled amounts of resistance, which allows you to control the flow of
electrons in a circuit.
Remember how electrons move and that they move more freely in a conductor. But some
kind of force must pull the electrons from one place to another. This attractive force between
positive and negative charges is an electromotive force called voltage. Negative electrons
move toward a positive voltage by way of a conductor.
An important combo: Electrons, conductors, and voltage
Say that you have a wire (a conductor), and you attach one of its ends to the positive terminal
of a battery and the other end of the wire to the negative terminal of the battery. Electrons
then flow through the wire from the negative to the positive terminal. This flow of electrons
is referred to as an electric current.
When you combine electrons, a conductor, and voltage you create an electric current in a
form that you can use. To help you picture how conductors and voltage affect the flow of
electric current in a wire, think of how water pressure and pipe diameter affect the flow of
water through a pipe. Here’s how this analogy works:
Increasing water pressure causes more water to flow through the pipe. This is analogous to
increasing voltage, which causes more electrons to flow, producing greater electric current.
Using a larger diameter pipe allows more water to flow through the pipe for a given amount
of pressure. This is analogous to using wire with a larger diameter, which allows more
electrons to flow for a given voltage, producing greater electric current.
3. Terminology of Basic Electronics
Before we begin.
As with any field of study, electronics has its own lingo. Some terms deal with electricity and
units of measure such as voltage. Other terms are tools you use in projects or electronics
parts, such as transistors. Here is a plethora of the terms you’ll run into in your electronics
life. Knowing these terms will help you become electronics fluent.
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Alkaline battery: A type of non-rechargeable battery.
Alternating current (AC): Current in which the direction of the flow of electrons cycles
continuously from one direction to the other and back again.
Amplitude: The amount of voltage in an electrical signal.
Anode: The positive terminal of a diode.
Bandwidth: the highest frequency signal that you can reliably test, measured in megahertz
(MHz).
Battery: A power source that uses a process called electrochemical reaction to produce a
positive voltage at one terminal and a negative voltage at the other terminal. This process
involves placing two different types of metal in a certain type of chemical.
Biasing: Applying a small voltage to the base of a transistor to turn the transistor partially on.
Bipolar transistors: A common type of transistor.
Buss: A common connection point.
Cable: Groups of two or more wires protected by an outer layer of insulation, such as a
common power cord.
Capacitance: The ability to store electrons, measured in farads.
Capacitor: A component that provides the property of capacitance (the ability to store
electrons) in a circuit.
Cathode: The negative terminal of a diode.
Circuit: A series of wires connecting components so that a current can flow through the
components and back to the source.
Cladding: A very thin sheet of copper that you glue over a plastic, epoxy, or phenolic base to
make a printed circuit board.
Closed circuit: A circuit where wires are connected, and current can flow.
Closed position: The position of a switch that allows current to flow.
Cold solder joints: A defective joint that occurs when solder doesn’t properly flow around
the metal parts.
Commutator: A device used to change the direction of electric current in a motor or
generator.
Components: Parts used in electronics projects, such as a battery or transistor.
Conductor: A substance through which electricity can move freely.
Connector: Metal or plastic receptacles on a piece of equipment that cable ends fit into; an
example of a connector would be a phone jack in your wall.
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Continuity: A test you perform with a multimeter to establish whether a circuit is intact
between two points.
Conventional current: The flow of a positive charge from positive to negative voltage; the
reverse of real current.
Current: The flow of an electrical charge.
Cycle: The portion of a waveform where the voltage goes from its lowest point to the highest
point and back again is one cycle. This cycle is repeated constantly while the waveform is
running.
Diode: Components that limit the flow of current to one direction.
Direct current (DC): Current in which the electrons move in only one direction, from the
negative terminal through the wires to the positive terminal, the electric current generated by
a battery is an example of direct current.
Double-pole switches: A type of switch that has two input wires.
Double-pole, double-throw switch (DPDT): A type of switch that has two wires coming
into the switch and four wires leaving the switch.
Double-pole, single-throw switch (DPST): A type of switch that has two wires coming into
the switch and two wires leaving the switch.
Electricity: The movement of electrons through a conductor.
Electromagnet: Some form of coiled wire around a piece of metal (typically an iron bar).
When you run current through the wire, the metal becomes magnetized. When you shut off
the current, the metal loses that magnetic quality.
Electromotive force: An attractive force between positive and negative charges, measured in
volts.
Electron: A negatively charged particle.
ESD: electrostatic discharge
Frequency: A measurement of how often an AC signal repeats (the symbol for frequency is
f)
Gain: The amount that a signal is amplified (the voltage of the signal coming out divided by
the voltage of the signal coming in).
Ground: A connection in a circuit used as a reference (zero volts) for a circuit.
Heat sink: A piece of metal that you attach securely to the component you want to protect.
The sink draws off heat and helps prevent the heat from destroying the component.
Hertz (Hz): The measurement of the number of cycles per second in alternat ing current.
High signal: In digital electronics, a signal at any value higher than zero (0) volts.
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I: The symbol for current.
IC: integrated circuit.
Impedance: The measure of opposition in an electrical circuit to a flow of alternating
current.
Inductance: The ability to store energy in a magnetic field (measured in Henries).
Inductors: Components that provide the property of inductance (the ability to store energy in
a magnetic field) to a circuit.
Infrared temperature sensors: A kind of temperature sensor that measures temperature
electrically.
Input/Output ports: (also called I/O ports) Connections on a microcontroller through which
signals are sent or received.
Insulator: A substance through which electrons are unable to move freely.
Integrated circuits (ICs): Components (often called a “chip”) that contain several small
components such as resistors or diodes.
Inverter: A type of logic gate that has only one input.
Inverting mode: A process by which an op amp flips an input signal to produce the output
signal.
Jack: A type of connector.
Joule: A unit of energy.
Lithium battery: A type of battery that generates higher voltage than other types, at about 3
volts. Lithium also has a higher capacity than alkaline batteries.
Live circuit: A circuit to which you’ve applied voltage.
Logic gate: An integrated circuit that takes input values and determines what output value to
use based on a set of rules.
Low signal: In digital electronics, a signal is at or near zero (0) volts.
Microcontroller: A programmable circuit.
Multimeter: A electronics testing device used to measure such things as voltage, resistance,
and amperage.
Negative Temperature Coefficient (NTC) thermistor: A resistor whose resistance
decreases with a rise in temperature.
Nickel-cadmium battery (NiCad): The most popular type of rechargeable battery.
Nickel-metal hydride battery (Ni-MH): A type of rechargeable battery.
N-type semiconductor: A semiconductor with contaminates added that causes it to have
more electrons than a pure semiconductor.
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OHM: A unit of resistance (the symbol for ohm is Ω).
OHM’s Law: An equation that allows you to calculate voltage, current, resistance, or power.
One-time programmable (OTP): OTP microcontrollers can only be programmed once.
Open circuit: A circuit where a wire is disconnected, and no current can flow.
Open position: The position of a switch that prevents current from flowing.
Operational amplifier: An integrated circuit used to boost an audio or other signal. An
operational amplifier performs much better than an amplifier made from a single transistor.
For example, an op amp can provide uniform amplification over a much wider range of
frequencies than can a single-transistor amplifier.
Oscilloscope: An electronic device that measures voltage, frequency, and various other
parameters for waveforms.
Oscillator: A circuit that generates waveforms.
Pad: Contact points on a printed circuit board used for connecting components.
Photoresist: (also called sensitizer or resist) A light-sensitive chemical layer used in making
circuit boards.
Piezoelectric effect: The ability of certain crystals — quartz and topaz are examples — to
expand or contract when you apply voltage to them.
PN junction: When regions containing boron and phosphorus are next to each other in a
semiconductor, a PN junction is created.
Positive temperature coefficient (PTC) thermistor: A device whose resistance increases
with a rise in temperature.
Potentiometer: A variable resistor that allows for continual adjustment of resistance from
virtually no ohms to some maximum value.
Power: The measure of the amount of work that electric current does while running through
an electrical component measured in Watts.
Precision resistors: A type of resistor with low tolerance.
Prescaler: A device that extends the useful operating frequency of a frequency counter.
Proton: A positively charged particle.
P-type semiconductor: A semiconductor with contaminates added that cause it to have fewer
electrons than a pure semiconductor.
Pulse: A signal that alternates between high and low very rapidly.
Pulse width modulation: A method of controlling the speed of a motor that turns voltage on
and off in quick pulses. The longer the “on” intervals, the faster the motor goes.
R: The symbol for resistance.
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RC time constant: A formula used to calculate the time it takes to fill a capacitor to twothirds or discharge it to one-third of its capacity.
Real current: The flow of electrons from a negative to a positive voltage.
Relay: A device that acts like a switch in that it closes or opens a circuit depending on the
voltage supplied to it.
Resistance: The measurement of the ability of electrons to move through a material.
Resistor: A component you add to a circuit to reduce the number of electrons flowing
through the circuit.
Schematic: A drawing showing how components in a circuit are connected by wires.
Semiconductor: A material, such as silicon, that has some of the properties of both
conductors and insulators.
Semiconductor temperature sensors: A kind of temperature sensor that varies the output
voltage depending on temperature.
Sensors: Electronic components that sense a condition or effect such as heat or light.
Series circuit: A circuit in which the current runs through each component sequentially.
Short circuit: Where two wires are accidentally connected together, and current goes through
them rather than completing the circuit as intended.
Sine wave: An output signal.
Single-pole switch: A type of switch that has one input wire.
Single-pole, double-throw switch (SPDT): A type of switch that has one wire coming into
the switch and two wires leaving the switch.
Slide switch: A type of switch you slide forward or backward to turn something (such as a
flashlight) on or off.
Solar cell: A type of semiconductor that generates a current when exposed to light.
Soldering: The method you use in your electronics projects to assemble components on a
circuit board to build a permanent electrical circuit; instead of using glue to hold things
together, you use small globs of molten metal called solder.
Soldering iron: A wand-like tool that consists of an insulating handle, a heating element, and
a polished metal tip used to apply solder.
Solid wire: A wire consisting of only a single strand.
Square wave: An output signal.
Static electricity: A form of current that remains trapped in an insulating body.
Stranded wire: Two or three small bundles of very fine wires, each wrapped in insulation.
Stray capacitance: A condition where electric fields occur between wires or leads in a circuit
that are placed too close together and electrons are stored unintentionally.
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Sweep generator: A device that produces signals that are somewhat different from the ones
that a standard generator puts out in that it sweeps the frequencies up and down.
Terminal: A piece of metal to which you hook up wires
Thermistor: A resistor whose resistance value changes with changes in temperature.
Thermocouple: A type of sensor that measures temperature electrically.
Tolerance: The allowed variation, expressed as a percentage, in the value of a component
due to the manufacturing process.
Traces: Wires on a circuit board that run between the pads to electrically connect the
components together.
Transistor: A device composed of semiconductor junctions to control the flow of electric
current.
V: The symbol for voltage; also commonly represented by E.
Variable capacitor: A capacitor that consists of two or more metal plates separated by air.
Turning the knob changes the capacitance of the device.
Variable coil: A coil of wire surrounding a movable metal slug. By moving the slug, you
change the inductance of the coil.
Voltage: An attractive force between positive and negative charges.
Voltage divider: A circuit that uses voltage drops to produce voltage lower than the supply
voltage at specific points in the circuit.
Voltage drops: The resulting lowering of voltage when voltage pulls electrons through
resistors (or any other component), and the resistor uses up some of the voltage.
Voltage spike: A momentary rise in voltage.
Watt hour: A unit of measure of energy; the ability of a device or circuit to do work.
Waveform: Voltage fluctuations such as seen in a sine wave or square wave.
Wire: A long strand of metal, usually made of copper, that you use in electronics projects.
Electrons travel through the wire to conduct electricity.
Wire gauge: A measurement of the diameter of a wire.
Zinc-carbon batteries: A low quality, non-rechargeable battery.
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4. Types of Electronic Components
There are many various electronic components, and it is difficult to be covered in one
manual, so we will examine the most important, common, and widely used components in
electronics.
Electronic components are divided into groups:
 Passive components - Very important and essential parts but they can’t amplify the
voltage.
 Electromechanical components - Contains moving parts.
 Active components - Used to amplify the voltage. They are also called
semiconductors.
 Optoelectronics components - Emit or receives light, IC integrated circuits
electronic chips that contains complete circuits manufactured by high techniques.
With this manual we will only investigate the basics of components. Its operation depends on
simple electrical and magnetic properties, these elements are essential in any electronic
circuit.
You need to know about the essential electrical components and how they work together to
create incredible modern electrical systems.
The Basic Electrical Components are:
Resistors
Capacitors
Light Emitting Diode (LED)
Transistors
Inductors
Integrated Circuit (IC)
Circuit Breaker
Fuse
Switch
Transformer
Electrical Wires & Power Cables
Battery
Relay
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Motor
5. Resistors
I didn’t understand the resistor in the beginning. It seemed like it didn’t do anything! It was
just there, consuming power. But eventually, I learned that the resistor is extremely useful.
You’ll see resistors everywhere. And as the name suggests, they resist the current. But you
are probably wondering: “What do I use it for?“ You use the resistor to control the voltages
and the currents in your circuit.
Let’s say you have a 9V battery and you want to turn on an LED. If you connect the battery
directly to the LED, lots of current will flow through the LED! Much more than the LED can
handle. So, the LED will become very hot and burn out after a short amount of time. But – if
you put a resistor in series with the LED, you can control how much current is going through
the LED.
A standard LED can only handle up to around 20-30 mA. If the current it much bigger than
that, the LED will quickly die. Let’s say the LED in the circuit above needs 15 mA to give a
good light, and it has a voltage drop of 2 volts. (These values should be specified by the
supplier when you buy an LED.) If you have a 9 V battery that you would like to power it
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with, which resistor value do you need? The voltage specified for the LED is the voltage drop
the LED will have under normal conditions. That means you know you will have 2V over the
LED.
To find the resistor value, we start by finding the voltage drop over the resistor. Since there is
a 2-volt drop over the LED, there will be a 7V drop over the resistor (9V - 2V equals 7V).
You have 7V over the resistor, and whatever number of current flows through it will also
flow through the LED. So, by setting the resistor value to a value that gives you 15 mA,
you’ll also get 15 mA through the LED. To find the necessary resistor value we use Ohm’s
law. By placing your hand over the R in the Ohm’s law triangle, you get that Resistance.
(R) equals voltage (V) divided by current (I).
This means you get: R = 7V / 0.015 A = 467Ω470Ω is a standard value close enough, so by
choosing this resistor value you decide that the current flowing in your circuit is 15 mA. It is
easy to assume that a resistor, as the name suggests, will resist electricity that flows through
it, and you would be correct in that assumption too! Any situation that demands the flow of
current to be controlled at the desired level will require a resistor.
Here are two scenarios that better explain what a resistor does. In both cases, we will be
turning on a LED:
Scenario 1 – Without Resistor
You have the power supply on one side. You connect the LED on the other end. The full
force of the electricity hits the bulb. This overloads the LED, eventually burning it out
completely.
Scenario 2 – With Resistor
You have the power supply on one side. You connect this to a resistor. The resistor, in turn,
connects to the LED bulb. Electricity flows through the resistor and into the bulb. You can
control the amount of electricity that needs to flow to the bulb. As a result, the LED won’t be
overloaded and won’t burn out.
 Function: Resistors are used to reduce current flow in certain percentages according to
the resistance value.
 Unit of measurement: Resistance is measured by ohm Ω.
 Features: Resistors vary depending on the value of the resistance (Ohms) and power
(watts), size and percentage error
 Damage signs: Burning, Breaking, Color change.
 Test Method: The multimeter is used to read the resistance value. We set the
multimeter to the ohm position and connect the multimeter’s terminals with the
resistor’s ones. Read the displayed value.
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Color code in resistors: Resistance manufacturers rely on the color method to determine the
value of resistance. See figure 1 below for the colour chart of resistors.
Types of resistors:
Potentiometer (Variable Resistor)
Reduce current’s flow (as usual resistors), except we can change its value manually.
Memristor
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This element changes its resistance according to the value of the voltage directed to it, this is
a new technology that may change the electronics industry considerably in the future, except
that this element is not used in the known devices we have so far.
6. Capacitors
You can think of a capacitor as a battery with very low capacity. You can charge and
discharge it, just like a battery. The capacitor is often used to introduce a time-delay in a
circuit. For example, to blink a light. But it’s also useful for removing noise in an audio signal
or make the power supply of a circuit more stable. Capacitors come as polarized and nonpolarized capacitors. The biggest difference is that with the polarized capacitor, you have a
positive and a negative pin and you need to make sure to connect them correctly. You can
connect non-polarized capacitors any way you want.
So, which one to choose?
You never need your capacitor to be polarized. But for larger values, the capacitors are made
with a material that makes them polarized. So, sometimes you don't have any choice but to
use a polarized one. For example, by connecting a capacitor in parallel with a resistor and an
LED, the capacitor can store energy and use the energy after the battery is disconnected. This
creates a “fading out” effect of the LED.
If a resistor is like a cushion, that is used to control the flow of electricity, then capacitors are
like small rechargeable batteries that store small amounts of charge in them. Capacitors do
two things at the same time:
They allow AC, or Alternating Current, to flow through them.
They resist the flow of DC, or Direct Current, through them.
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By doing so, they can stabilize almost any circuit.
There are four types of capacitors that are primarily used:




Polarized capacitors – these have a positive and negative terminal.
Non-polarized capacitors – these do not have any positive or negative terminals.
Electrolytic capacitor - that has polarity (+/-).
Ceramic capacitor - does not have polarity.
Features of Capacitor to take note:
 Signs of damage: swelling from top or explosion, wax release, dehydration, strong
odor.
 Test method: Most modern multimeters have a capacitor measurement option, and it
is an easy way to test. We put the cursor on fµ, put Multimeter’s ends on the
capacitor’s ends and read the result. The proper capacitor will give a close reading of
the one that is written on it.
Note: Capacitors are sometimes highly charged. The charge should be discharged by
resistance.
Voltage-stabilizing integrated circuits stabilize the voltage at a given value and these circuits
are way much better than Zener diodes in maintaining the voltage at a specified level.
Most voltage stabilizers are connected to capacitors to improve output stability.
Properties: Voltage stabilizers usually overheat during operation, so they must be attached to
the heat-dissipation metal/Aluminum piece.
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7. Light Emitting Diode (LED)
A Light Emitting Diode – or LED for short – is a small component that lights up when
current flows through it. Sometimes you use it for simple tasks like indicating that your
circuit has power, that the circuit is working or that the circuit has failed. But you can also
combine several LEDs to create simple 7-segment displays that can display numbers or use
them to make cool light decorations. If you combine enough LEDs in a square, you can even
use them to show images.
The LED exist in many different colors; Red, green, blue and many more. There is also a
special type of LED called RGB. This is an LED where a red, green, and blue LED has been
combined into one package. The colors mix, so by controlling the intensity of each of the
three colors you can create a wide spectrum of different colors.
To use an LED, you need to connect it in a circuit with a resistor. The reason you need the
resistor is to make sure the LED does not burn up. A common LED can only handle a very
low current. If you don’t use a resistor to control the current, your LED will quickly die and
become unusable.
LEDs were briefly mentioned while describing “Resistors.” LEDs are just like bulbs, except
that they are extremely reliable. You can find them on practically every appliance in your
home that features some kind of indicator light. A typical LED bulb can last decades with no
sign of dying.
Since they are so reliable, they are used to indicate the state of current at any point in a
circuit. An important task like checking the output voltage or current on a circuit becomes
simpler with these light-based indicators.
 Work: What distinguishes LED from other diodes Is the release of the light when the
current passes through it, this happens when the diode is in the forward bias.
 Characteristics: LEDs vary in size, shape, capacity and operating voltage, if you want
to operate them with a higher voltage than the operating voltage, then you need to
know the value of the appropriate resistance that must be connected with the LED to
protect it from over-voltage.
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8. Diodes
Diodes allow the current to pass through one way if it is forward biased (the
anode with the positive terminal and the cathode with the negative one), and it prevents it
from passing when it is reverse biased. Diodes are used in voltage and converting it from AC
to DC. Diodes differ by its power, how much current it can handle and what will it do.
Test method:
There is a diode testing option with a multimeter. Connect the anode to the positive terminal,
and the cathode to the negative terminal of the multimeter. It will show you value. If you
connect them vice versa it will show you a zero or OL (open loop). If we connect the anode
with the positive side of the power and the cathode with the negative side, the similar charges
will repel, which makes the resistance of the diode small, and lets the current pass through it.
And that is called the forward bias. If we connect the cathode with the positive side of the
power, and the anode with the negative side, similar charges will attract, which makes the
resistance of the diode very high and doesn’t allow the current to pass through it. And that is
called the reverse bias.
Characteristics curve:
We must understand the working of the active components using the curves. This helps the
circuits’ designers a lot when they design a new electric circuit. Curves explains the relation
between the voltage and the current at the ends of the component. The right side of the curve
presents the forward bias region.
The bridge converts the AC voltages to DC voltages. Rectifying Bridge consist of 4 diodes
connected with each other in a specific way (as in the following
figure). Each bridge has its own current that it can handle.
Test method: if you imagine the bridge as 4 diodes, it will be easy to test.
Follow the terminals and test them with the diodes test method.
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Types of Diodes
Schottky diode
Function: Schottky diode works at voltages less than 200 volt and current reaches 300
amperes. So, it is suitable for the high current low voltage applications.
Zener Diode
Function: Zener Diode cuts off excess voltage (specified by the manufacturer) and is usually
used to stabilize the voltage at a particular point in the circuit at a certain value which is
written on the Zener diode.
Photodiode
Work: it allows current to pass in the opposite direction only when it’s directed to its
light-sensitive area.
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9. Transistors
The Transistor
This is the component that seems to be the hardest to understand when starting out. At least it
was for me. But don’t worry, it’s not that hard. A transistor is like a switch that is controlled
by an electrical signal. It has three pins named (B)ase, (C)ollector, and (E)mitter. If you have
a small current lowing from base to emitter, you turn it on. With no current, it is off. To get
current flowing you need about 0.7V from base to emitter. Unlike a normal switch that only
has two states (ON or OFF), the transistor can also be “partly on” by controlling the current
that goes through its base. A bit of current on the base produces a current of maybe 100 times
more (depending on the transistor) through the Collector and Emitter. You can use this effect
to build an amplifier.
A simple way to understand transistors is to think of a switch. A basic switch has an “on” and
an “off” state. These are controlled by the position of the switch, which is changed manually.
A transistor is a more advanced switch that has multiple output states. Unlike a switch, you
cannot change these states manually. The only way to switch the transistor between various
states is to run current through it. By controlling the current that flows through the transistor,
you can control the output state to achieve your desired results. Transistors can be tested by a
multimeter, which is a fairly easy way and can be relied upon if we suppose that the transistor
is bipolar junction consists of 2 diodes.
 Important note: The resistance between B and E is slightly larger than the resistance
between B and C.
Types of Transistors
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BJT
BJT Transistor is the most important invention of the last century, its invention led to the
advancement of electronics in a large and amazing way.
 Function: The transistor amplifies, connects, and disconnects electrical signals (acts as
an electronic switch).
The terminals of the BJT bipolar transistor are:
B: Base
C: Collector
E: Emitter
 Features: In the bipolar transistor, the conductivity between the C and E terminals
depends on the current passes through B. If the current passing in B is zero, the
resistance of the transistor is very high between C and E. When the IB current reaches
a certain value, the resistance of the transistor becomes very small. The BJT transistor
resistance changes linearly, so it is suitable for enlarging analog signals.
The transistor works at one of three operating situations:
The cut-off region in which the resistance between C and E is very high (as if it is an open
switch). The saturation region where the resistance between C and E is very low (as if the
switch is closed ON)
The active region in which the resistance between C and E is an average value.
 Disadvantages: One of the drawbacks of BJT is that it does not withstand high
voltages or high temperatures. It also consumes a higher amount of energy than other
types of transistors.
FET
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 Function: The FET transistor works like a normal transistor (BJT) except that its
conductivity depends on the voltage value at the G (end) and not on the base current
as in the BJT transistor. The FET transistor species are various and widely studied.
We can’t study all of them.
The terminals of the FET transistor are:
G: Gate
D: Drain
S: Source
 Features: Easily manufactured in integrated circuits. Input resistance is very high,
therefore consumes less power and emits less heat. Withstands higher temperatures
than BJT. It can work with digital signals faster than the BJT and emits less noise.
 Disadvantages: it does not enlarge linearly (in other words it is not suitable for analog
signal amplification).
UJT
 Function: it is like the JFET transistor except it differs in size and the manufacturing
material. It is easy to manufacture oscillators’ circuits using this type of transistor.
 Features: it cannot amplify an analog signal because it is not constant. It is suitable to
generate pulses with low or medium frequencies. The UJT transistor is rarely used
nowadays.
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10. Inductors/Coils
An inductor is just a coil of wire. If you take a wire and wind, it up into a coil, you have
created an inductor. When you apply a current through the coil, a magnetic field is created
around it, and this field stores energy. When the current through the inductor stays the same,
the inductor does nothing. It just lets the current pass through, just like it was a normal wire.
But when the current through the inductor changes, the built-up energy in the magnetic field
will resist this change by changing the resistance of the inductor.
Resistance to change is a good thing, for example to create a filter to reduce noise.
If the wire is wound around a magnetic core (for example iron), the magnetic field becomes
much stronger. A transformer is a component made up of two inductors wound around the
same magnetic core.
The transformer is a classical component used to reduce the voltage in power supplies. If you
constantly change the current through one inductor (the input), the change in magnetic field is
picked up by the other inductor (the output).
If the input inductor has 1000 windings, and the other inductor has only 100, then the
resulting voltage on the output inductor is ten times less than the input voltage.
Inductors are just as complicated as transistors. Like transistors, inductors are used to build
complex electrical systems. Unlike transistors, though, inductors are essentially coils of
wire that are wound around other components. They are used as filters.
Of all the electrical components mentioned on this page, you will most likely not use
inductors for basic circuit designs. Nonetheless, depending on the project you are working on,
inductors might appear in the circuit’s design.
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 Function: The coils generate a magnetic field when an electric current passes through
it.
 Features: coils are rarely used in electronic circuits but frequently used in
communications circuits, frequencies and transmitting and receiving operations. Each
coil has its own number of twists and type of material the rings wrapped around it.
There are coils with air heart, metallic heart, or paper heart.
 Test Method: coils have very small resistance. The multimeter can, therefore, be used
and the coil's resistance can be measured from both ends. Some of the coils are
damaged by cutting and their resistance would be very high.
 Damage: Some other coils have interruptions between their twists and this type of
damage is difficult to detect by multimeter, so we use other devices like LCR meter
and Ring Tester.
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11. Integrated Circuit (IC)
An integrated circuit is any kind of circuit that is integrated onto a chip. It can be a radio
transmitter, a microcontroller, an audio amplifier, or any other circuit you can think of. By
making a circuit on a small chip, it’s much easier to make advanced projects. Let’s say you
want to make a tracking device for your car. You can find a GPS chip for positioning, a GSM
chip to send text messages, and a microcontroller chip to control everything. To figure out
exactly what a specific IC does, you need to check its datasheet. The datasheet is a document
that comes with every IC. You can find the datasheet for almost any IC by just searching for
the chip name + “datasheet” in Google. The datasheet explains what each of the pins does,
how much voltage it needs, and often contains an example circuit to show you how to
connect it.
The 555 timer is a very useful and popular Integrated Circuit. You can use it to blink a light,
to create sound, to create a clock signal, add a countdown timer and a lot of other things. A
simple example is to blink an LED. By carefully selecting the values of the capacitor and
resistors on the input side, you can control how fast the light should blink.
Timer 555 is an integrated circuit that can be used in many digital applications. It has two
main uses.
 Non-stable Circuit: The timer generates pulses (square) at a frequency determined by
the elements connected with it. These pulses are used to adjust synchronization in
digital circuits.
 Monostable Circuit: The timer adjusts the width of pulses.
With rapid advances in electronic circuits installing circuits with separated elements isn’t
feasible anymore in terms size, time, price and functionality, which results in an idea to
manufacture full circuit consisting of tens of thousands of elements in single chip (IC
Integrated Circuit), each chip has number and specification sheet explaining how to Connect
and operate the integrated circuit, the number of integrated circuits is very large and we will
only cover the most common types of integrated circuits.
Integrated circuits are electrical components that combine or integrate numerous electrical
components, including the previously mentioned ones. One IC can act like a transistor, while
another IC can act like a resistor.
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An IC is like a ready-made chip that you can use to complete the project you want to build
without having to use lots of single transistors or capacitors. As you upgrade from using basic
components to integrated circuits, you will find that it is almost always easier to use ICs for
your entire project than using individual components.
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12. Circuit Breaker
A circuit breaker is a vital mechanical switching device that protects your electrical
equipment from short circuit and power surges. It automatically detects a faulty condition and
interrupts the harmful current flow from reaching the sockets. Every circuit breaker has 2
coils; a closing coil that closes the circuit and a tripping coil to trip the circuit.
There are 2 types of contacts in a circuit breaker. One is a moving connection that uses stored
energies to make and break the circuit. Another one is fixed contact, comprising a spring that
holds the moving contact after closing.
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13. Fuses
Fuse is a friend of the circuit breaker as it helps the breaker in protecting the electric
equipment from power overload. Fuse is the wire that gets heated up and damaged when the
circuit encounters a power surge. In this way, the current stops flowing.
It comes in different varieties to sustain the different amounts of currents. The main
components of a standard fuse are metal-fuse elements, support body, contacts, and
connection. The metal-fuse elements can be made from alloy, copper, aluminum, zinc, silver,
etc.
 Function: The fuse protects electronic circuits and devices from overcurrent. It




contains a sensitive wire that melts if the current exceeds the specified amount of the
fuse.
Unit of measurement: The fuse is measured in ampere A, the maximum current that a
fuse can withstand before it breaks.
Features: Fuses are easily damaged. There are different shapes and sizes, and some
are slow to cut.
Damage signs: internal burning, discoloration, wire cut.
Test Method: The multimeter is used to test the fuse, and the easy way is to set the
multimeter to the ring out position or the resistance position by connecting the
multimeter terminals to the fuse. The fuse is damaged if the multimeter shows an OL
sign.
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14. Switch
The switch is a component that connects one pin to another. For current to flow through a
circuit, there needs to be a path from the positive of the battery to the minus of the battery. If
you build a simple circuit with an LED and a resistor and connect this to a battery, your LED
will light up. If you disconnect the positive of the battery from the circuit, the LED turns off.
The switch is nothing more than a way to connect and disconnect two or more things. For
example, to make a light-switch or a keyboard.
Yes! We all know what a switch is! Let’s get to its technical definition. The primary purpose
of a switch as a device is to break the current, interrupt the current, and supply current from
one conductor to another. The “On and off” mechanism is used to perform this task. There are
4 main classifications of a switch:  Single Pole Single Throw (SPST)
 Single Pole Double Throw (SPDT)
 Double Pole Single Throw (DPST)
 Double Pole Double Throw (DPDT)
Various operative technologies are used in a switch, such as:




Rocker switches
Slide switches
Pushbutton switches
Rotary switches
 Test method: it is easy if you know its internal connection. You will need a
multimeter in the ring out mode (sound only).
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15. Transformer
It is an electric device that changes the levels of AC current. It consists of 2 coils of wire
connected by an iron core. The transformer uses mutual induction of two windings to convert
the electric energy from one circuit to another. It also converts the power between circuits
with different voltage levels without altering the frequency.
You can find both small and large transformers in the market. There are basically 2 types of
transformers:  Step-up transformer – its secondary coil has more winding than the primary coil
 Step-down transformer – You guessed it right! Its primary coil has more winding than
the secondary coil.
 Unit of measurement: The transformer does not have a unit of measurement. But its
function can be determined by knowing the appropriate input voltage and output
voltage when operating the transformer in volts or by measuring the resistance of both
primary and secondary coils.
 Test Method: The resistance of the two inductors (input inductor and output one) can
first be measured using a multimeter. They both have a small resistance. Noticing that
the value of the primary inductor is higher than the value of the secondary inductor. It
is advisable to try the transformer by connecting a suitable input voltage to it and then
measuring the output voltage on both ends of the secondary coil.
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16. Electrical Wires & Power Cables
It’s almost impossible to make an electrical structure without electrical wires and cables.
Electrical wires do the work of connecting a device to the power source through cables. You
need wires to install every device, be it switches, sockets, LEDs, or anything else.
When multiple electrical wires are bundled or run side by side for transmission and
distribution of electrical current, it is known as an electrical power cable. When you can’t use
overhead lines, electrical cables come in handy to transmit high voltage current. A cable has
3 primary components:
 conductor,
 sheath, and
 dielectric.
Silicon is found in nature and in sand in large quantities. Scientists have noted that silicon
electrical resistance is high so, they added other materials to silicon to control its resistance.
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17. Battery
Batteries act as a source of electric power through the electrochemical cells. Each cell
consists of an anode (-), cathode (+), and electrolyte. It works on the principle of
electrochemical reaction as the cells create the flow of electrons through a chemical reaction.
In layman’s terms, batteries are portable containers that store electrical potential energy.
There are two types of cells in a battery:
 primary rechargeable cells and
 secondary non-rechargeable cells.
Solar Cell
 Work: The solar cell generates a continuous DC (voltage, current, and power) when
directed toward sunlight (it uses Sunlight)
 Measurement unit: Volt and its power is usually measured in watts.
 Characteristics: The solar cell is a low-efficiency element in energy conversion. The
solar cell's efficiency doesn’t exceed 25% while the highest efficiency ever achieved
in a solar cell is 45%.
 Test Method: Place the solar cell under bright light and measure its voltage by using a
multimeter.
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18. Relays
Earlier relays were used as amplifiers in the long-distance telegraph circuits. Relays evolved
to solve more purposes in the technology sector and telephone exchange. They are
electromechanical switches that use low-power signals to control the circuit. Its essential
components are an armature, a spring, an electromagnet, and a series of electrical contacts.
The circuit inside a relay uses magnetic connections instead of electric ones.
 Function: Relay controls a switch in a Magnetic way. When an electric current passes
through a coil, the adjacent switch changes its state from disconnection to connection




or vice versa, making it very useful for control.
Unit of measurement: The voltage of the coil is measured in Volt while the maximum
current passing through the switch is measured in Ampere.
Features: The relays vary in the number and quality of the switches inside. The
common type of relay has 5 ends: two ends of the coil. One common end of the
switch is called C, a connected end with C (without applying voltage called NC), and
disconnected end from C (without applying voltage called ON).
Disadvantages: relay is a large element, makes a noise when changing its status, and
consumes a certain amount of energy, and generates a large magnetic field.
Test: Relay testing is an easy process. You will need a multimeter on the beep mode.
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19. Electric motor
Motors convert electrical energy into mechanical energy. It comprises of a stator, conduit
box, eye bolt, rotor, enclosure, and bearings. Motors are more efficient in energy supply than
their pneumatic and hydraulic counterparts. Therefore, it is the most common part amongst
all the electrical machinery.
There are different types of motors available in the market. They are:





AC inductance motors
Brushless permanent magnet synchronous motor
Stepper motor
DC motors
Switched reluctance motor.
 Function: The motor converts electric power into a rotational motion.
 Types: There are three main types of small electric motors used in electronics and
robots.
o The DC motor is the simplest type, and the rotation direction can be
changed by changing the polarity of the feeder, and it has only two ends.
o Stepper motor: Its speed and angle of rotation can be accurately controlled,
and usually it has five ends.
o Servo motor: is a developed version of the DC motor. It has a sensor and
gears and usually has three ends.
 Test Method: Test the internal coils using a multimeter or connect the appropriate
voltage and see the motor rotation.
 Features: motor speed is measured by several cycles per minute rpm. Motor power
can be increased using gears gearbox, but rotation speed will decrease a lot.
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20. Amplifier
Work: The operational amplifier can be used to perform many tasks in electronic circuits.
such as:
 Inverting amplifier: Amplifying signal and reversing its polarity.
 Non-inverting Amplifier: Amplifying signal without reversing polarity.
 Isolation Amplifier: Connecting two circuits and isolating power transitions between
them.
 Summing Amplifier: Summing multiple voltage input and output them on one
terminal.
 Oscillator: oscillator circuit to generate a sinusoidal signal
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21. Understanding circuit diagrams
Below is the simplest of a circuit diagram and Schematic symbols.
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Power Supply Schematic Symbols
Schematic
Symbol
Symbol Identification
Description of Symbol
Single Cell
A single DC battery cell of 0.5V
DC Battery Supply
A collection of single cells forming a
DC battery supply
DC Voltage Source
A constant DC voltage supply of a
fixed value
DC Current Source
A constant DC current supply of a
fixed value
Controlled Voltage Source
A dependent voltage source
controlled by an external voltage or
current
Controlled Current Source
A dependent current source
controlled by an external voltage or
current
AC Voltage Source
A sinusoidal voltage source or
generator
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Electrical Grounding Schematic Symbols
Schematic
Symbol
Symbol Identification
Description of Symbol
Earth Ground
Earth ground referencing a common
zero potential point
Chassis Ground
Chassis ground connected to the
power supplies earthing pin
Digital Ground
A common digital logic circuit
ground line
Resistor Schematic Symbols
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Schematic
Symbol
Symbol Identification
Description of Symbol
Fixed Resistor (IEEE Design)
A fixed value resistor whose resistive
value is indicated next to its
schematic symbol
Fixed Resistor (IEC Design)
Potentiometer (IEEE Design)
Three terminal variable resistance
whose resistive value is adjustable
from zero to its maximum value
Potentiometer (IEC Design)
Rheostat (IEEE Design)
Two terminal fully adjustable
rheostat whose resistive value varies
from zero to a maximum value
Rheostat (IEC Design)
Small variable resistors for mounting
onto PCB’s
Trimmer Resistor
Thermistor (IEEE Design)
Thermal resistor whose resistive
value changes with changes in
surrounding temperature
Thermistor (IEC Design)
Capacitor Schematic Symbols
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Schematic
Symbol
Symbol Identification
Fixed Value Capacitor
Fixed Value Capacitor
Description of Symbol
A fixed value parallel plate nonpolarized AC capacitor whose
capacitive value is indicated next to
its schematic symbol
Polarized Capacitor
A fixed value polarized DC capacitor
usually an electrolytic capacitor
which must be connected to the
supply as indicated
Variable Capacitor
An adjustable capacitor whose
capacitance value can be varied by
means of adjustable plates
Inductor and Coil Schematic Symbols
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Schematic
Symbol
Symbol Identification
Description of Symbol
Open Inductor
An open inductor, coil or solenoid
that generates a magnetic field
around itself when energized
Iron Core Inductor
An inductor formed by winding the
coil around a solid laminated iron
core indicated by solid lines
Ferrite Core Inductor
An inductor formed by winding the
coil around a non-solid ferrite core
indicated by dashed lines
Switch and Contact Symbols
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Schematic
Symbol
Symbol Identification
Description of Symbol
SPST Toggle Switch
Single-pole single-throw toggle
switch used for making (ON) or
breaking (OFF) a circuit current
SPDT Changeover Switch
Single-pole double-throw
changeover switch used for changing
the direction of current flow from
one terminal to another
Pushbutton Switch (N.O)
Normally open contacts pushbutton
switch – push to close, release to
open
Pushbutton Switch (N.C)
Normally closed contacts pushbutton
switch – push to open, release to
close
SPST Relay Contacts
Electromechanical relay with internal
single-pole single-throw toggle
contacts
SPDT Relay Contacts
Electromechanical relay with internal
single-pole double-throw changeover
contacts
DPST Relay Contacts
Electromechanical relay with internal
double-pole single-throw toggle
contacts
DPDT Relay Contacts
Electromechanical relay with internal
double-pole double-throw
changeover contacts
DIP Switch Assembly
PCB mounted DIP switch with 1-to10 toggle switches either single-pole,
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double-pole, rotary or with a
common terminal
Semiconductor Diode Symbols
Schematic
Symbol
Symbol Identification
Description of Symbol
Semiconductor Diode
Semiconductor PN-junction diode
used for rectification and high
current applications
Zener Diode
Zener diode used in its reverse
voltage breakdown region for voltage
limiting and regulation applications
Schottky Diode
Schottky diode consisting of an ntype semiconductor and metal
electrode junction for low voltage
applications
Transistor Symbols
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Schematic
Symbol
Symbol Identification
Description of Symbol
NPN Bipolar Transistor
Characterized as being a lightly
doped p-type base region between
two n-type emitter and collector
regions with the arrow indicating
direction of conventional current
flow out.
PNP Bipolar Transistor
Characterized as being a lightly
doped n-type base region between
two p-type emitter and collector
regions. Arrow indicates direction of
conventional current flow in.
Darlington Pair Transistor
Two bipolar transistor NPN or PNP
connected in a series common
collector configuration to increase
current gain
N-JFET Transistor
N-channel junction field effect
transistor having an n-type
semiconductive channel between
source and drain with the arrow
indicating direction of conventional
current flow
P-JFET Transistor
P-channel junction field effect
transistor having a p-type
semiconductive channel between
source and drain with the arrow
indicating direction of conventional
current flow
N-MOSFET Transistor
N-channel metal-oxide
semiconductor field effect transistor
with an insulated gate terminal which
can be operated in depletion or
enhancement mode
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P-MOSFET Transistor
P-channel metal-oxide
semiconductor field effect transistor
with an insulated gate terminal which
can be operated in depletion or
enhancement mode
Photodevice Schematic Symbols
Schematic
Symbol
Symbol Identification
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Light Emitting Diode (LED)
A semiconductor diode which emits
coloured light from its junction when
forward biased
7-segment Display
A 7-segment display used common
cathode (CC) or common anode
(CA) for displaying single numbers
and letters
Photodiode
A semiconductor device which
allows current to flow when exposed
to incident light energy
Solar Cell
P–N junction photovoltaic cell
transducer which converts light
intensity directly into electrical
energy
Photoresistor
Light dependent resistor (LDR)
which changes its resistive value
with changes in light intensity
Indicator Lamp or Light Bulb
A filament lamp, indicator or other
which emits visible light when a
current flows through it
Opto-isolator or Optocoupler
An Opto-isolator or Optocoupler
which uses photo-sensitive devices to
isolate its input and output
connections
Digital Logic Symbols
Schematic
Symbol
Symbol Identification
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NOT Gate
Logic gate with only one input and
one output and outputs a logic 1
(HIGH) when input is 0 (LOW) and
outputs a 0 when input is 1
(Inverter)
AND Gate
Logic gate with two or more inputs
which outputs a logic 1 (HIGH)
when ALL of its inputs are at logic 1
(HIGH)
NAND Gate
Logic gate with two or more inputs
that outputs a logic 0 (LOW) when
ALL of its inputs are HIGH at logic
1 (Equivalent to NOT + AND)
OR Gate
Logic gate with two or more inputs
which outputs a logic 1 (HIGH)
when ANY (or both) of its inputs are
at logic 1 (HIGH)
NOR Gate
Logic gate with two or more inputs
that outputs a logic 0 (LOW) when
ANY (or both) of its inputs are
HIGH at logic 1 (Equivalent to NOT
+ OR)
XOR Gate
Exclusive-OR gate with two inputs
that outputs a logic 1 (HIGH)
whenever its two inputs are
DIFFERENT
XNOR Gate
Exclusive-NOR gate with two inputs
that outputs a logic 1 (HIGH)
whenever its two inputs are the
SAME (NOT + XOR)
SR Flip-Flop
Set-Reset Flip-flop is a bistable
device used to store one bit of data
on its two complementary outputs
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JK Flip-Flop
JK (Jack Kilby) Flip-flop has the
letter J for Set and the letter K for
Reset (Clear) with internal feedback
D-type Flip-Flop
D (Delay or Data) Flip-flop is a
single input flip-flop which toggles
between its two complementary
outputs
Data Latch
Data latch stores one data bit on its
single input when EN enable pin is
LOW and outputs the data bit
transparently when the EN enable
pin is HIGH
4-to-1 Multiplexer
A Multiplexer passes the data on one
of its inputs pins to a single output
line
1-to-4 Demultiplexer
A Demultiplexer passes the data on
its single input pin to one of several
output lines
Schematic Symbols for Inductors
Schematic
Symbol
Symbol Identification
A fixed value air-core inductor, coil,
solenoid or choke which uses either a
self-supporting form or a solid or
hollow ceramic, plastic, or some
other form of non-magnetic material
Air-core Inductor
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as its inner core for high frequency
applications
Iron-core Inductor
A fixed value solid iron-core
inductor formed by winding the coil
around a solid laminated iron core,
indicated by the symbols two solid
lines, to concentrate the magnetic
field generated around itself when
energized
Ferrite Core Inductor
A fixed value inductor formed by
winding the coil around a non-solid
compressed powdered ferrite core or
bead indicated by the symbols two
dashed lines
Tapped Inductor
An inductor coil with either one or
more fixed value connections called,
taps, along its length for impedance
matching and tank circuits
Adjustable Inductor
An adjustable or continuously
adjustable inductor whose selfinductance value can be varied from
some minimum value to a maximum
value when adjusted
Schematic Transformer Symbols
Schematic
Symbol
Symbol Identification
Air-core Transformer
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Single-phase air-core voltage
transformer with two inductive coils
wrapped closely together around a
solid or hollow plastic non-magnetic
core for radio frequency applications
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Iron-core Transformer
Single-phase iron-core voltage
transformer (VT) formed by winding
the two coils around a solid
laminated iron core, indicated by the
symbols two solid lines, for the
transfer of electrical energy from one
winding to the other changing an AC
voltage from high to low or low to
high
Power Transformer
Single-phase power transformer (PT)
shown as two interconnecting circles
for the transmission and distribution
of electrical power from high to low
or low to high
Ferrite-core Transformer
Single-phase transformer formed by
winding the two coils around a nonsolid compressed ferrite core to
decrease eddy current losses, hum
and increase the magnetizing flux.
Used mainly in toroidal transformers
Step-down Transformer
Single-phase step-down isolation
transformer which converts a higher
primary winding voltage into a lower
secondary winding voltage by an
amount determined by the turns
ratios of the transformer
Step-up Transformer
Single-phase step-up isolation
transformer which converts a lower
primary winding voltage into a
higher secondary winding voltage by
an amount determined by the turns
ratios of the transformer
0o Phase Shift
Inline dot orientation used to indicate
the 0o phase-shift between the
primary and secondary windings
used to correctly parallel connect
transformers together
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180o Phase Shift
Diagonal and opposite dot
orientation used to indicate the
180o phase-shift between the primary
and secondary windings resulting in
voltage and current inversion
Center-tapped Transformer
Single-phase center-tapped voltage
transformer with either primary,
secondary or both sides divided into
two windings allowing for multiple
voltage points. Primary center tap
allows for dual supplies, while
secondary center tap is useful in
rectifier circuits
Multi-tapped Transformer
Single-phase Multi-tapped voltage
transformer either primary,
secondary or both allowing for
multiple voltage connection and
take-off points
Multi-load Transformer
Single-phase voltage transformer
with one or more magnetically
coupled secondary windings to
supply individual loads, or the
secondary windings may be
connected in parallel for a greater
current, or in series for a higher
voltage
Dual-winding Transformer
Single-phase voltage transformer
consisting of two transformers on the
same core, with the primary and
secondary windings of each
transformer wound on the same
magnetic core. For use in both low
and high voltage supplies and psu
applications
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Iron-core Autotransformer
Single-phase step-down
autotransformer with one single coil
for both the primary and the
secondary windings wrapped around
a magnetic iron-core and one or more
fixed tapping points giving a
secondary voltage equal to or less
than the primary voltage
Iron-core Autotransformer
Single-phase step-up autotransformer
with one single coil for both the
primary and the secondary windings
wrapped around a magnetic iron-core
and one or more fixed tapping points
giving a secondary voltage equal to
or more than the primary voltage
Variac
Single-phase variable
autotransformer called a variac with
one single tapping point which can
be adjusted to produce a variable
secondary voltage. Does not provide
isolation
Current Transformer
Step-down current transformers (CT)
wound, toroidal or bar type which
provides electrical isolation between
the high-current carrying conductor
and metering device
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22. Electronics Formulas You Should Know
Ohm’s Law and Joule’s Law are commonly used in calculations dealing with electronic
circuits. These laws are straightforward, but when you’re trying to solve for one variable or
another, it is easy to get them confused. The following table presents some common
calculations using Ohm’s Law and Joule’s Law. In these calculations:
V = voltage (in volts)
I = current (in amps)
R = resistance (in ohms)
P = power (in watts)
Ohm’s Law
Unknown Value
Formula
Voltage
V=IxR
Current
I = V/R
Resistance
R = V/I
Power
P = V x I or P = V2/R or P = I2R
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Joule’s Law
Quantity
Formula
Unit
Q=C
Charge
×
Coulomb (C)
V
𝑄
Capacitance
C =𝑉
Inductance
VL𝑑𝑡 = – L
Henry (L or H)
Voltage
V=IR
Volt (V)
Current
I =𝑅
Resistance
R =𝐼
ohm (𝜔)
Power
P = VI
Watt (W)
𝑑𝑖
𝑉
Farad (F)
Ampere (A)
𝑉
1
Conductance
G=𝑅
Z2 = R2 + (xL – xc)2
Impedance
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ohm (𝜔)
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Resonant Frequency
1
f = 2𝜋√𝐿𝐶
Hertz (Hz)
Understanding Ohm’s Law
Say that you’re wiring a circuit. You know the amount of current that the component can
withstand without blowing up and how much voltage the power source applies. In order you
have to come up with an amount of resistance that keeps the current below the blowing-up
level.
In the early 1800s, George Ohm published an equation called Ohm’s Law that allows you to
make this calculation. Ohm’s Law states that the voltage equals current multiplied by
resistance, or in standard mathematical notation.
V=IxR
Taking Ohm’s Law farther
Remember your high school algebra? Remember how if you know two things (such as x and
y) in an equation of three variables, you can calculate that third thing? Ohm’s Law works that
way; you can rearrange its elements so that if you know any two of the three values in the
equation, you can calculate the third. So, here’s how you calculate current: current equals
voltage divided by resistance, or
IR
V=
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You can also rearrange Ohm’s Law so that you can calculate resistance if you know voltage
and current. So, resistance equals voltage divided by current, or
RI
V=
So far, so good. Now, take a specific example using a circuit with a 12-volt battery and a light
bulb (basically, a big flashlight). Before installing the battery, you measure the resistance of
the circuit with a multimeter and find that it’s 9 ohms. Here’s the formula to calculate the
current:
IR
V
9 ohms
12 volts == = 1.3 amps
The power of Ohm’s Law
also expressed that power is related to voltage and current using this equation:
P = V x I; or power = voltage x current
What if you don’t know the voltage?) Because V = I x R, you can substitute I x R into this
equation, giving you P = I2 x R; or power = current squared x resistance
You’re probably happy to hear that online calculators can make these calculations much
easier. Try searching on www.google.com using the keyword phrase “Ohm’s Law Calculator”
to find them.
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23. The Sixth Sense of Electronics
Respect for the power of electricity is necessary when working with electronics. In this
section, we look at keeping yourself, and your electronic projects, safe. This is the one
section that you really should read from start to finish, even if you already have some
experience in electronics.
The sixth sense of electronics isn’t about seeing dead people. In this case, the sixth sense is
common sense, the smart way that helps you stay among the living. Common sense is that
voice inside you that tells you not to stick your fingers in an empty lamp socket without first
unplugging the lamp. No book can ever teach you common sense. You must cultivate it like
an exotic flower. But a few words from the wise may help get you started in your quest for
electronics common sense.
For starters:
Never assume. Always double-check.
If you’re not sure about how to do something, read up on it first.
Don’t take chances.
Never let your guard down.
By far, the single most dangerous aspect of working with electronics is the possibility of
electrocution. Electrical shock results when the body reacts to an electrical current — this
reaction can include an intense contraction of muscles (namely, the heart) and extremely high
heat at the point of contact between your skin and the electrical current. The heat leads to
burns that can cause death or disfigurement. Even small currents can disrupt your heartbeat.
The degree to which electrical shock can harm you depends on a lot of factors, including your
age, your general health, the voltage, and the current. But no matter how young and healthy
you may be, voltage and current can be deadly, so it’s important that you understand how
much they can harm you.
Electricity = voltage + current
To fully understand the dangers of electrical shock, you need to know the basics of what
makes up electricity. Electricity is made up of two elements: voltage and current. Voltage and
current work together and in ways that directly influence the severity of electrical shock.
Is it AC or DC?
You can describe electrical current as being either of the following Direct (DC): The electrons
flow one way through a wire or circuit. Alternating (AC): The electrons flow one way, then
another, in a continuing cycle.
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If this stuff is new to you, you may want to go back to the beginning of this manual for a
more detailed discussion.
Household electrical systems in South Africa operate at between 220 – 240 volts AC. This
significantly high voltage can, and does, kill. You must exercise extreme caution whenever
you work with it. Until you become experienced working with electronics, you’re better off
avoiding circuits that run directly off household current. Stay with circuits that run off
standard-size batteries, or those small plug-in wall transformers.
The main danger of household current is the effect it can have on the heart muscle. High AC
current can cause severe muscle contraction, serious burns, or both. Many electrocution
accidents occur when no one is around to help the victim.
Burns are the most common form of injury caused by high DC current. For example, don’t be
lulled into thinking that because a transistor battery delivers only nine volts, it’s harmless. If
you short the terminals of the battery with a piece of wire or a metal coin, the battery may
overheat and can even explode! In the explosion, tiny battery pieces can fly out at high
velocity, burning skin or injuring eyes. Trying to not get electrocuted. Most electrocution
accidents happen because of carelessness. Be smart about what you’re doing, and you will
significantly reduce the risk of being hurt by electricity.
Here are a few handy electrocution prevention tips:
Avoid working with open AC-operated circuits.
Physically separate the AC and DC portions of your circuits.
Make sure you secure all wiring inside your project.
Ground AC-operated circuits.
Be serious and focused while you’re working around electricity.
Don’t work where it’s wet.
Practice the buddy system.
Getting a first aid chart
Helping someone who has been electrocuted may require cardio-pulmonary resuscitation,
otherwise known as CPR. Be sure that you’re properly trained before you administer CPR on
anyone. Otherwise, you may cause more harm than good.
One type of everyday electricity that is dangerous to both people and electronic gizmos is
static electricity. They call it static because it’s a form of current that remains trapped in some
insulating body, even after you remove the power source. With conventional AC and DC
current, static electricity disappears when you turn off the power source.
Static electricity of just a few thousand volts, a mere tingle to you (because the current is so
very, very low), can cause great harm to sensitive electronic components. Static electricity
hangs around until it dissipates in some way. Most static dissipates slowly over time, but in
some cases, it gets released all at once.
Lightning is one of the most common forms of static electricity.
24. Two most important tools to use with Electricity.
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Soldering is the method you use in your electronics projects to assemble components on a
circuit board to build a permanent electrical circuit. Instead of using glue to hold things
together, you use small globs of molten metal called solder. The metal not only provides a
physical joint between the wires and components of your circuit, but it also supplies the
circuit with the conductivity it needs to work.
The multimeter is the basic tool for anyone working in electronics. You use a multimeter to
take a variety of electrical measurements — hence the term “multi.” With this one tool, you
can measure:






AC voltages
DC voltages
resistance
current going through a circuit.
continuity (whether a circuit is broken or not)
Depending on the model, you may also be able to test the operation of diodes,
capacitors, and transistors to see if they’re good.
All multimeters come with a pair of test leads, one black and one red (black is for the ground
connection; red is for the positive connection). Each test lead comes equipped with a metal
probe. For small, pocket units the test leads come permanently attached to the meter.
25. Conclusion
Electronics is a renewed and accelerated beautiful science, an applied science in which ideas
turn into reality. Knowing electronic elements and their work is an important step in the field.
Electronics are divided into many specializations such as analog circuits, digital circuits,
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control, communications, sensors industry, integrated circuits, small computer systems, and
with the great development of science, electronics can be used in every home. Starting with
the simplest things that everyone uses to the end of the most complex, such as television,
radio, digital cameras, cars, aircraft, medical devices, computers, and many other devices that
cannot be counted.
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