Lecture Noted - Electrical Technology

ELECTRICAL TECHNOLOGY

LECTURE NOTES

ELECTRICAL
TECHNOLOGY

AN AUGMENTED REALITY EXPERIENCED

PREPARED BY

AIZURA BINTI ABU BAKAR
HAZREEN BINTI OTHMAN

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LECTURE NOTES - ELECTRICAL TECHNOLOGY

TERBITAN EDISI 2020

BUKU “LECTURE NOTES - ELECTRICAL TECHNOLOGY” ADALAH
SEBAGAI RUJUKAN DA N BAC A A N U M U M T E RU TA M A K E PA DA
PENSYARAH DAN P E L A JA R POLITEKNIK DAN KOLEJ KOMUNITI
M A L AYS I A BAG I MENGAPLIKASIKAN AMALAN TERBAIK DALAM
PERLAKSANAAN KAEDAH P E N G A JA R A N DA N P E M B E L A JA R A N
BERKONSEPKAN TEKNOLOGI AUGMENTED REALITY.

EDITOR
MOHD ROZAIMIN ABDUL HAMID

PENULIS
AIZURA BINTI ABU BAKAR
HAZREEN BINTI OTHMAN

DITERBITKAN OLEH
UNIT PEMBELAJARAN DIGITAL
BAHAGIAN INSTRUKSIONAL DAN PEMBELAJARAN DIGITAL
JABATAN PENDIDIKAN POLITEKNIK DAN KOLEJ KOMUNITI ARAS 6, GALERIA PJH,
JALAN P4W, PERSIARAN PERDANA, PRESINT 4,
62100 PUTRAJAYA

Website : www.celt.edu.my
E- mail : [email protected]

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1 INTRODUCTION TO

ELECTRICAL CIRCUITS

1.1 INTRODUCTION

There are two types of electrical signals, alternating current (AC), and direct current
(DC). With alternating current, the direction electricity flows throughout the circuit is
constantly reversing. You may even say that it is alternating direction.

Electricity is typically defined as having a voltage and
a current rating. Voltage is obviously rated in Volts and
current is rated in Amps. Electricity can also be defined
in terms of resistance and watts. Most basic electronic
circuits use DC electricity.
This chapter explains about the basic principle of electric
circuits and its connections. The learning outcome for
this chapter are the students should be able to explain
clearly basic electrical quantities, types of electrical
circuits,
electrical power, electrical energy and solve related
problems related to electric circuits.

1.2 ELECTRIC

Electric is a type of energy that occurs due to the movement of electrons and protons
in an oscillating pattern. Electricity is a source of power that is often used to provide
light, heat buildings, or power on devices such as computers. Electric energy can be
created impact from action as friction, heat and electromagnetic field. Electric energy
can be change into other form of energy such as

a) Light energy – lamp
b) Heat energy – Iron
c) Sound energy – Radio
d) Kinetic energy - Motor

There are two types of electric which is the static electric and dynamic electric.
a) Static electricity – A situation where there is no electron movement in certain
direction.
b) Dynamic electricity – A situation where there is an electron movement in
certain direction

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1.2.1 ELECTRICAL QUANTITIES AND BASIC QUANTITIES

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1.2.2 ASIC QUANTITIES AND UNITS IN

ELECTRICAL Quantities
The table shows electrical quantities which are used in electronics. The relationship
between quantities can be written using words or symbols (letters), but symbols are
normally used because they are much shorter; for example, V is used for voltage, I for
current and R for resistance. As a word equation:
Voltage = current x resistance
The same equation using symbols: V =I x R

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1.2.3 RESISTANCE

The resistance of given material depends on the physical properties of the material.
There are 4 factors that influence the value of resistance:

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Example 1.2.3.1

Calculate the resistance of aluminium wire with length 60km and radius of the wire is
15cm. Given resistivity of aluminium is 0.3µΩm.

Example 1.2.3.2
Determine the resistivity value of the aluminium wire with 1.5Ω resistance. The
aluminium wire with length is 10km and diameter of the wire is 200mm.

Example 1.2.3.3
An aluminium wire has a length of 2 km and a radius of 5 mm. If the 5V voltage is
supply tothe circuit, and the resistivity of the wire is 0.28µΩm, calculate the amount
of the currentflows through the aluminium.

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1.3 ELECTRIC CIRCUIT

An electric circuit is an interconnection of electric components such that electric
charge (current) ismade to flow along a circuit, usually to perform some useful task.
The components in an electriccircuit can take many forms, which can include elements
such as resistors, capacitors, switches,transformers and electronics. The resistoris
the simplest of passive circuit elements. Electric circuitis a combination of conductor
or cable which allows current to flow from voltagesources toelectrical components or
load such as resistance. There are two types of electric circuit:
i. Complete circuit
ii. Incomplete circuit

1.3.1 COMPLETE CIRCUIT

It is called as a basic circuit or simple circuit. It is closed end connection that allows
currentto flow through from the source and back to sources again. The circuits must
have voltage supply (V), electric current (I) and resistance (R).

1.3.1 INCOMPLETE ELECTRIC CIRCUIT

Circuit without one of three components either voltage sources or load resistance. The
current flow will never happen with perfect in incomplete circuit. There are two types of
incomplete circuit: Open circuit and Short circuit.
i . Openci rc u i t
Circuit without the load, so there will be no current flow. Value of resistant in this
circuit is a higher.

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ii. Short circuit
A short circuit is an abnormal connection between two nodes of an electric
circuit intendedto be at different voltages. In circuit analysis, a short circuit is a
connection between twonodes that forces them to be at the same voltage. In an
ideal short circuit, this means thereis no resistance and no voltage drop across
the short.

1.4 OHM’S LAW

Ohm’s law states that the current through a conductor between two points is directly
proportionalto the potential difference across the two points. If the value of resistance
is constant andvalue of voltage increase so the value of current can be increase.
Mathematically the equationfor Ohm’s law is as equation below.

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The relationship between current and voltage is as shown using the graph at Figure
1.4.1. This is the situation for constant value of resistance and temperature.

For the inconstant or changing value of resistance, the relationship between voltage
and current are nonlinear as graph shown in Figure 1.4.2 below.

The ohm’s Law formula can be interpret into another form to help students remember.

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Example 1.4

Calculate the value of the current flows in the circuit if the given resistance is 25kΩ
and the supply voltage is 9V. If the resistance value is increase to 50kΩ, calculate
the new amount of current flows in the circuit.

1.5 ELECTRIC POWER

Electric power is define as work done in one unit of time. Resistor dissipates energy in
the form of heat. So power absorbed by the resistor is given by equation below.

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Electric power can also be measured in
horse power.(h.p)

1.6 ELECTRICAL ENERGY

Electrical energy is energy that is caused by moving electric charges. Since the electric
charges aremoving, this is a form of kinetic energy. The faster the electric charges are
moving the moreelectrical energy they carry. Meter kilowatt-hour is used to measure
the total of electrical energy.

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The unit for electric energy is Kilowatt hour (kWh) or Joule (J). When the current flow,
electron inthe conductor will repel each other and it will produce heat and thus causing
the cable that is used heating up.
Work is the energy absorbed to supply load 1 kW for 1 hour. Watt is the power
used when 1Acurrent flows between two points that have 1 volt potential. A unit for
work is Joule. This is equal to the energy produced to 1 Coulomb charge flows by 1
ohm resistance. Total energyused to flow 1A current for 1 second by 1 ohm resistant
is called 1 Joule. It is can be calledas 1 watt second, which is 1 watt power used for 1
second.
Example 1.6
A toaster use 5A current from 240 V supply for 15 minutes. Calculate:
i. Power used
ii. Energy absorbed in kJ

1.7 ESISTOR CIRCUIT ANALYSIS

Resistor can be connected in three different types. There are series, parallel and
combination of series and parallel.

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1.7.1 Series Circuit

Series circuit is referring to the connection of the resistor in the circuit. The resistors
are connected from end to end as in Figure 1.7.1.1.

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Example 1.7.1

1.7.2 PARALLEL CIRCUIT

The parallel circuit is a connection of resistor which is against between each other.
The resistors connected in parallel are shown in Figure 1.7.2.1.

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1.7.3 COMBINE CIRCUIT

Most of electric circuits are the combination of series and parallel circuit. Both formula
of series and parallel circuit will be used to determine the value of current, voltage and
total resistance. Figure shown below is the example for combination circuit.

Example 1.7.3

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1.8 KIRCHOFF’S LAW

Kirchoff’s law is used to solve more difficult electric circuit, for example the circuit
whichhaving more than one power supply. Two types of Kirchoff’s Law there are
K i r ch o f f’s cu r r e n t l a w a n d K i r ch o f f ’ s v o l t a g e l a w .

1.8.1 KIRCHOFF’S CURRENT LAW

Kirchoff’s current law is also known as the first law of Kirchoff’s law. Kirchoff’s current
law stated that the algebraic sum of all the currents entering and leaving a same node
is equal.Therefore, the sum of the current into a node total current in is equal to the
sum of the currents out of the node (total current out) as shown in figure below.

In mathematic expression its can be stated as equation below.

1.8.2 KIRCHOFF’S VOLTAGE LAW

Kirchoff’s voltage law also known as the second order of Kirchoff’s law. This law stated
that the sum of the voltage drop and voltage source around a closed path is equal to
zero.

In mathematic expression its can be stated as equation below.

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Example 1.8

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TUTORIAL

1. Calculate the resistance of the aluminium bar with 10m length, cross section
area 8cm x 1cm and 0.0269 µΩm resistivity.

2. A copper base conductor with 2500cm length and 1.75 µΩm resistivity. Calculate
the diameter of the conductor when the resistor is 3.5 kΩ.

3. The heating element with 150Ω resistance, 250 cm length and 0.7 mm. Calculate
the resistivity.

4. The resistivity of the cylinder aluminium conductor is 280 µΩmm, 1 mm radius and
30Ω resistance. Calculate the length.

5. Referring to the figure below, determine the current flow in the conductor.

6. What is the voltage in the circuit if current flows in the circuit is 0.5 A and resistance
is 0.8Ω

7. What is the current of a circuit if resistance is 3 Ω and voltage is 15V.
8. Calculate the energy in Joule and Kilowatt hour for:
a. A 60W lamp switched on for 8 hours
b. A 3kW kettle switched on for 5 minutes
9. Calculate the current flow in the circuit with 10 Ω resistance and 15V voltage supply.

Then, calculate the current if the resistance is increasing to 10 kΩ
10. Calculate the power losses when the current is 5mA through resistance 6kΩ.
11. A kettle with resistance 40 Ω and current 2.4 A. Calculate the power.
12. A toaster with 5A current and 240 V supply was on for 15 minutes. Calculate ,
i.Powerused
ii. En e r g y i n k J
1 3. A rice cooker with 3.45 kW power, 230 V voltage. Calculate:
i.Current
ii. R e s i s t a n c e
iii. Energy if the rice cooker is switch on for half an hour

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14. Calculate the amount of voltage supplied by a battery in a circuit given below.

15. Calculate the:

i. Potential difference, V
ii. Power, P
iii. Electrical energy if the circuit switch on for

2 hours
16. Based on the circuit diagram, calculate;

i. Total resistance.
ii. Total voltage, VT
iii. Voltage drop in the resistance R3, the voltage

divider law.
17. Based on the figure, find;
i. Total Resistance.
ii. Voltage, R2.
iii. Current R2 and R3.
iv. Total power and power dissipated in R1.

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18. Based on the figure, find;
i. Total Resistance.
ii. Voltage, R3 using Voltage divider law.
iii. Current R2 and R3.
iv. Total power
v. Powerdissipated in R4.
19. Based on the figure, determine the

value of:
i. Total Resistance.
ii. Current R2 and R3
iii. Voltage, R4.
iv. Total power
v. Power dissipated in R1
20. Based on figure below, calculate total resistance, RT

21. Based on figure below, the voltage across R1 = 72 V. Specify the following values:
i. The current flow for each resistor

R1,R2,R3 an R4
ii. The voltage across each resistor R2,R3

and R4
iii. Supply Voltage, V

22. Define the First and second order of Kirchoff’s Law.
23. Based on Figure below, calculate the current value of each branch and voltage

drop in each resistor using Kirchoff’s Law

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2 INDUCTOR, CAPACITOR,

ALTERNATING CURRENT CIRCUITS
AND THREE PHASE SYSTEM

2.1 INTRODUCTION

This chapter explains about the inductors, capacitors and AC circuits. The learning
outcome for these chapters are, the students should be able to apply correctly the
basicprinciples of inductors, capacitors and AC circuits that contains R, L and C. And
be able tosolve problems related to inductors, capacitors and AC circuit.

2.1.1 INDUCTOR

An inductoris a component designed to store electrical energy in the form of an
electromagnetic field. Inductors will oppose changes in current, both in direction and
amplitude. Energy is stored in a magnetic field in the coil as long as current flows.
Applications for inductor are mostly in wave shaping devices, frequency filters and
current regulator. Basic construction of inductors is a wire wrapped around a core
material

Inductor is a spiral structure coil of wire which creates a magnetic field when current
passes through it. The magnetic field through the middle of the coil is directed from
left to right,and is highly intensified.

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2.1.2 PRINCIPLES OF ELECTROMAGNETIC INDUCTION

Electromagnetic Induction – The creation of an electromotive force and current within
a conductorby varying the magnetic field affecting the conductor. There are three
conditions necessary for induction:
1. A Conductor (Coil)
2. A Magnetic Field
3. Relative Motion (Expanding or Collapsing field)
If a conductor is passed through (relative motion) a magnetic field, current will be
induced into the conductor. Or if an expanding or collapsing magnetic field (relative
motion) cuts across a conductor, current will also be induced.

2.1.3 INDUCTANCE

Inductance is the physical property of a circuit that opposes any change in current
flow.There are two types of inductances there are self-Inductance (L) and mutual-
Inductance (M)

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2.1.3.1 SELF INDUCTANCE (L)

Self-inductance is a phenomenon in which a change in electric current in a coil
produces an induced emf in the coil itself. It will occur when a current flow in the coil
causing the changing of flux in the winding. The electromotive force (emf) produced
is opposite direction with the direction of the applied voltage.

2.1.3.2 MUTUAL INDUCTANCE (M)

Mutual inductance is the changing current through one coil will produces emf in
another coil is called mutual induction

When current flow in the first loop, flux will be produce in the first coil. The continuous
current causes flux flow to the next coil and then generate emf in the second coil. Emf
produced in second coil will cut the conductor and produce the emf in second loop

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2.2 INDUCTOR CIRCUIT ANALYSIS

Inductors can be connected in two different ways, series and parallel.

2.2.1 SERIES INDUCTORS

Inductors are said to be connected in series when they are chained together in a
straight line, end to end as shown in figure 2.2.1.
To calculate the total inductance using this formula:

2.2.2 PARALLEL INDUCTORS

Inductors connected in parallel are opposite to each other as shown in figure 2.2.2.
The same voltage is applied to each component but the total current will split into
each branches. To calculate the total inductance:

Example 2.2.2
Calculate the total inductance (LT) for the three coil when the value of each inductor is
0.1H, 10mH, 100µH if the connection is in:
a ) Series
b ) Parallel

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2.2.3 INDUCTANCE REACTANCE, XL

The alternating current (AC) is changing continuously which in turn produced
continuous opposed induces emf as well. The opposition to the current flow is called
inductance reactance. The symbol for inductance reactance is XL and the unit is Ohm
(Ω).The Inductance Reactance can be calculate using:

Example 2.2.3
A coil with 0.2H connected with AC 200V, 50Hz. Calculate the inductance reactance
in the circuit

2.2.4 ENERGY IN INDUCTOR

Energy in the inductor can be calculated using the equation below. The unit for energy
is Joule (J)

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2.3 CAPACITOR

Capacitor is an electronic device, which is used to store electric charge or electrical
energy. A system of two conductors separated by air or any insulating material forms
a capacitor as shown below:

The principle of capacitor is based on the fact that the potential of a conductor is

greatly reduced and its capacity is increased without affecting the electric charge in it

by placing another earth connectedconductor or an oppositely charged conductor in its

neighbourhood. This arrangement is therefore ableto store electric charge. Capacitor

are designed to have large capacity of storing electric chargewithout having large

dimensions. Symbols: Unit: Farad (F)

There are many types of capacitor which is Dielectric Air Convertible Capacitor, Paper
Capacitor, Polyester Capacitor, Mica Capacitor, Ceramic Capacitor, Electrolytic
Capacitor and Tantalum Capacitor

The effects of capacitor as the electrical device in the circuit are to:

1. Increasing the circuit power factor.
2. Reducing the fireworks during the switch is on inside the circuit.
3. Reduce radio interference test in the starter circuit pendaflour light.
4. Strengthen the electric current.
5. Store electrical charges.

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2.3. CAPACITANCE

Capacitance is a characteristic of a capacitor to store electrical energy. It is define
as thequantity or amount of electric charge needed to make a difference between
the two plates.Capacitance of 1 Farad means a capacitor can store 1 coulomb of
electrical charge when voltage is applied to the capacitor is 1V. This can be simplified
in a formula.
Typically the unit use for capacitor is microfarad (µF) or pikofarad (pF). Table 2.6
show the equivalent value and unit for capacitor.

Three (3) factors affecting the value of the capacitance of a capacitor:

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2.4 CAPACITOR CIRCUIT ANALYSIS

The method of the capacitor circuit analysis is different with the method of circuit
analysis
for inductance. There are 3 types of circuit analysis in capacitor:
i. Series connection
ii. Parallel Connection
iii.Combination of series and parallel connection

2.4.1 SERIES CAPACITORS

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2.4.2 PARALLEL CAPACITORS

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2.4.3 CAPACITANCE REACTANCE, XC

2.4.4 ENERGY IN CAPACITOR

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2.5 ALTERNATING CURRENT (AC)

Ohm’s Law can also be applied to AC circuits. However, alternating currents and
voltages arecontinually changing. At the beginning of the cycle the voltage and current
are zero, building to peak positive values at 90°, before declining back to zero, and
then repeated in a negative direction.
It is therefore only possible to calculate instantaneous values of V or I throughout the
cycle. Peak or RMS values are normally used.
Alternating voltage can be generated in 2 ways:
1. Conductors cut the magnetic flux which is the conductor is moving and the magnetic

flux is stationary.
2. Magnetic flux cut the conductor where the flux is moving and conductor is stationary

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2.6 TYPES OF AC WAVEFORM

There are 3 types of waveforms in AC:
1. In Phase Waveform
Where two waveform are in the same phase but have different values of maximum
voltage(Vm)

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2.7 VECTOR/PHASOR DIAGRAM

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2.8 BASIC TYPES OF AC CIRCUIT

There are 3 basic types of AC circuit purely resistance, purely inductance and purely
capacitance.
1. Purely Resistance

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2.9 AC CIRCUIT ANALYSIS

2.9.1 SERIES RESISTANCE AND INDUCTANCE (RL)

The RL circuit is the combination between resistor and inductor in series.
-Current value is the same for each load

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2.9.3 SERIES RESISTANCE, INDUCTANCE AND CAPACITANCE (RLC)

The RLC circuit is the combination of resistor, indictor and capacitor in series with
AC supply. The current value is the same for each load. Thus, the current (I) be-
come the reference factor in the vector diagram.

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