Basic electrical and electronic principles

b
B
Basic
Principles of Electrical and Electronic
Engineering
O
O
K
L
E
T©MDinesh2016
By: DineshMahadawoo
For Diploma Y1 in MechanicalEngineering
Users
Certificate / Diploma Level Engineering
ELEMENTS:
1. Basic Electricity
2. Demonstrate knowledgeandapplicationsof basicelectrical
quantitiesandunits.
3. Demonstrate knowledgeof simplecircuitsanalysis
4. Demonstrate knowledgeof ACcurrent.
5. Demonstrate the basicunderstandingof three phase AC.
6. Demonstrate the basicunderstanding anduse of basictools
and instrumentsusedinappliedelectricity.

BLANK PAGE
©MDinesh Mechanical Department [Turn Over]

Handout 1 Week 1
Pg 3
E.1 Basic Electricity
1.0.1 INTRODUCTION
Electricity is a form of energy called electrical energy. It cannot be seen, heard,
touch or smell.
However the effects of electricity can be seen, heard, touch or smell.
EFFECTS OF ELECTRICITY
SIGHT SOUND
SMELL
FEEL SMELL

Handout 1 Week 1
Pg 4
E.1 Basic Electricity
1.0.2 WHAT IS ELECTRICITY?
Energy caused by the flow of charge in a conductor, called as electricity or
electric current or simply current.
Explanation
We all know everything is made of matter. Therefore electricity is matter.
 Matter is made up of :
 ATOMS
Made up of tiny particles called electrons and protons.
These particles have charges.
 Electron (negative charge)
 Proton (positive charge)
Structure of atom
Atoms are usually balanced and stable.
 number of electrons = number of protons
Atoms can lose or gain electrons to become ions.
 Gain electrons to become negative ions
 Lose electrons to become positive ions
These charged ion particles are responsible for electron
flow (electricity).

Assignment 1 Week 1
Pg 24
E.1 Demonstrateknowledge of electricity as an energy source
Q1 (a) Define the following terms.
(i) Electricity
(ii) Atoms
(iii)
Q2 (a) Explain difference between a cell and a battery?
ANSWER
ANSWER

Assignment 1 Week 1
Pg 25
1.2.0 The difference between electricity generated chemically and electricity generated from
electro-mechanically is explained.
(b) Draw the symbol of a battery and a cell.
Q3 Explain how energy is produced electromechanically?
Q4 (a) Explain difference between chemically generated electricity and
electromechanically generated electricity?
ANSWER
ANSWER
ANSWER

Handout 3 Week 3
Pg 27
1.3.0 The difference between direct current (D.C.) and alternating current (A.C.) is explained.
1.3.1 DC AND AC CURRENT
There are two types of electric current:
1. direct current - DC
2. alternating current - AC
1.3.2 DC CURRENT
DC current means electric current flows in one direction only.
Explanation
DC source: Battery / cell
The diagram below shows flow of current.
There are two types
1. Flow of electron (from negative to positive terminal)
2. Convectional current (positive to negative terminal)
Note
We use convectional current i.e. the direction of flow is positive.

Handout 3 Week 3
Pg 28
DC current has polarity i.e. positive terminal and negative terminal.
For example
Batteries indicating 2 V, 1.5 V and 9 V
+
_
2 V, 1.5 V and 9 V indicate a constant value. I.e. a steady voltage.
A graph of Voltage against Time can be obtained from an oscilloscope.
The graph obtain from a 9 V battery is shown below.
2 V means + 2 Volts
1.5 V means + 1.5 Volts
9 V means + 9 Volts
Terminal of the battery must be connected to a positive value
Terminal of the battery must be connected to ground i.e. 0 V
Symbol for DC

Handout 3 Week 3
Pg 29
1.3.3 DC GENERATOR
A DC generator produces DC current.
It is an electrical machine which converts mechanical energy into direct
current electricity.
Some examples of DC generator are shown below.
`
Dynamo
Portable DC generator
Permanent magnet
alternator
Permanentmagnet DC generator

Handout 3 Week 3
Pg 30
1.3.4 AC CURRENT
AC current mean electric current in which the flow of electric charge
changes direction or polarity, respectively, over time.
Explanation
AC source: Alternator or AC generator
Alternator / AC generator is an electrical machine which converts
mechanical energy into alternating electric energy.
A simple diagram showing flow of electron in an AC generator.
Note
AC current does has a ‘no’ set polarity.

Handout 3 Week 3
Pg 31
Why AC current has a reverse polarity?
In a direct current (DC) circuit, one pole is always negative, the other
pole is always positive and the electrons flow in one direction only.
AC generator is also used as well as DC generator. Both have their
utility in specific task.
For example
A motor is connected to an alternator to produce AC current. Simply you
can call it as a generator.
Motor uses fuel or diesel for combustion, like a car engine, coupled with
the alternator. Thus converting mechanical energy to AC current.
Symbol for AC
In an alternating current (AC) circuit the two poles alternate between
negative and positive and the direction of the electron flow reverses
periodically.
A graph of Voltage against Time of an AC generator can be obtained
from an oscilloscope.

Handout 3 Week 3
Pg 32
1.3.5 AC GENERATOR
A diagram showing an AC generator set
Engine couple with an alternator.
This type of generator is used to produce single phase voltage for
homes, shops and offices.
Larger generators with greater capacity are used for buildings, factories,
and industries.
Advantages
 Stable voltage
 Speed can be controlled, fuel can be save
Disadvantages
 Noisy
 More energy is needed to run the engine

Handout 3 Week 3
Pg 33
Some examples of AC generator are shown below.
`
Alternator
Manual AC generator
Portable AC generator
Permanentmagnet AC generator

Assignment 3 Week 3
Pg 35
Q1 (a) What does AC and DC stand for?
Explain with an aid of a diagram the function of an AC and DC
generator?
(b)
(c) What is the symbol for AC and DC?
ANSWER
AC
DC
ANSWER
ANSWER

Assignment 3 Week 3
Pg 36
Q2 Briefly explain in the differences between DC and AC?
ANSWER

Handout 4 Week 4
Pg 37
1.4.0 Applications of D.C. in battery operated appliances and applications of A.C. are stated
1.4.1 APPLICATIONS OF D.C.
DC power is widely used in low voltage applications. Mostly in battery
operated appliances.
Some examples are given below.
Cordless battery operated appliances
Rechargeable
electronictoothbrush
Electricshavers
Cordlessscrewdriver
Cordlessdrill

Handout 4 Week 4
Pg 38
1.4.0 Applications of D.C. in battery operated appliances and applications of A.C. are stated..
1.4.2 APPLICATIONS OF A.C.
AC power is widely used in household applications, workshop
machineries
Some examples are given below.
Household applications
Power tools
Electricfan
Arc welding Bench grinder
Air Con Heater
Power drill

Assignment 4 Week 4
Pg 39
1.4.0 Applications of D.C. in battery operated appliances and applications of A.C. are stated.
Q1 Give some applications of D.C. in battery operated appliances use
in home.
Q2 Give some applications of A.C. use in workshop.
ANSWER
ANSWER

Handout 5 Week 5
Pg 41
E.2
Demonstratethe knowledgeand applications of basic electrical
quantities and units.
2.1.0 The definition of resistance, voltage and power are given.
2.1.1 TERMS OF ELECTRICITY
Electricity cannot be weighed on a scale or measured in a container,
but certain electrical “actions” can be measured.
These actions or “terms” are used to describe electricity, voltage,
current, resistance and power.
Voltage is pressure
Current is flow
Resistance opposes
Power is the amount of work performed. It depends on the
amount of pressure and volume of flow.
Consider the diagram below.
Water Analogy

Handout 5 Week 5
Pg 42
E.2
2.1.2 BASICS ELECTRICAL QUATITIES
1. Voltage
Table showing unit small units and large units for voltage.
Note
A Voltmeter measures the difference in electrical pressure between
to points in volt.
A Voltmeter is used in parallel in a circuit.
Voltage is an electrical pressure, a potential force or in electric
charge between two points. It can push electric current through a
wire, but not through its insulation.
SI Unit Voltage is Volt
Symbol
Instrument: Voltmeter
V

Handout 5 Week 5
Pg 43
E.2
2. Current
Table showing unit small units and large units for current.
Note
An Ammeter measures current flow in ampere or amps, for short.
It is inserted in the path of current flow
A Ammeter is used in series in a circuit.
Current is electrical flow / flow of charge moving through a wire.
Current flows in a wire pushed by voltage.
SI Unit Current is Ampere
Symbol
Instrument: Ammeter
A

Handout 5 Week 5
Pg 44
E.2
3. Resistance
Table showing unit small units and large units for resistance.
Note
A special meter called Ohmmeter can measure resistance of device
in ohms when no current is flowing.
An Ohmmeter is used in a circuit when no current is flowing.
Resistance opposes current flow. It is like electrical “friction”. This
resistance slows the flow of current. Every electrical component or
circuit has resistance. And this electrical resistance changes
electrical energy into another form of energy – heat, light, motion.
SI Unit Resistance is Ohm
Symbol
Instrument: Ohmmeter
Ω

Handout 5 Week 5
Pg 45
E.2
4. Power
Table showing unit small units and large units for power.
Note
A Wattmeter is used to measure power in watts.
An Energy meter is measured in watt-hour.
Voltage and current is not measurements of electrical power and
work. Power in watts is a measure of electrical energy.
Power is the rate of work done or energy converted with time.
SI Unit Power is Watt
Symbol
Instrument: Wattmeter
W
1W = 1J/S

Assignment 1 Week 5
Pg 47
E.2
Q1 Define the following terms and give its SI Unit
(a) Voltage
(b) Current
(c) Resistance
(d) Work
(e) Power
(f) Electrical energy

Handout 6 Week 6
Pg 49
E.2
2.2.0 The instruments used to measure resistance, voltage and power are stated.
2.2.1 METERS
There are different types of meters use to measure voltage, current,
resistance and power.
Voltmeter, Ammeter and Ohmmeter are combined into a single tester
called a “multimeter”. Nearly all technicians in electrical/mechanical
use multimeters.
Multimeter can also use as an “AVO” meter, usually called CLAMP
Meter. The clamp is used to measure current.
A multimeter can be one of two types.
1. Analogue
Displays use a needle point to measure value on scale.
2. Digital
Displays shows measured value in actual numbers (digits).
INSTRUMENT MEASUREMENT SI UNITS
VOLTMETER VOLT V
AMMETER AMP A
OHMMTER OHM Ω
WATTMETER WATT W

Handout 6 Week 6
Pg 50
E.2
2.2.2 METERING FUNCTIONS
Three metering functions are combined in a typical digital multimeter.

Handout 6 Week 6
Pg 51
E.2
A Typical Analog Multimeter
Analog meters used a mechanical movement and are not suitable for
measurements in circuits with sensitive electronic components.

Handout 6 Week 6
Pg 52
E.2
A Typical Digital Multimeter (DMM)
Digital multimeters display the actual measured value and are
suitable for measurements in circuits with sensitive electronic
components.

Handout 6 Week 6
Pg 53
E.2
DDM Components
The main components are found in the front panel.
 Digital display
 Range selector
 Mode selector
 Input jacks

Handout 6 Week 6
Pg 54
E.2
DDM Mode selector

Handout 6 Week 6
Pg 55
E.2
DDM Display

Handout 6 Week 6
Pg 56
E.2
UNITS Modifier

Handout 6 Week 6
Pg 57
E.2
DDM Auto ranging

Handout 6 Week 6
Pg 58
E.2
DDM Auto ranging

Handout 6 Week 6
Pg 59
E.2
DDM Test leads and input jacks

Handout 6 Week 6
Pg 60
E.2
EXAMPLE

Assignment 2 Week 6
Pg 62
E.2
Q1 Name the following types of instruments and its use.
NAME
USE
NAME
USE
NAME
USE
NAME
USE

Assignment 2 Week 6
Pg 63
E.2
Demonstratethe knowledge and applications of basic electrical
Q2 What is the reading of the following meters below?
ANSWER
ANSWER
ANSWER

Handout 7 Week 7
Pg 65
E.2
2.3.0 Demonstrate the knowledge of current measuring units, measuring instrument and its
circuit connection.
2.3.1 MEASURING ELECTRICAL QUANTITIES
Voltmeter connected is always connected in parallel in an electrical
circuit.
A circuit diagram below shows how voltage is measured.
Connecting one lead of the voltmeter to the input side of a globe and the
other lead to earth results in a reading of the voltage present at the globe.

Handout 7 Week 7
Pg 66
E.2
circuit connection.
Ammeter connected is always connected in series in an electrical
circuit.
A circuit diagram below shows how current is measured.
To connect an ammeter, the circuit needs to be disconnected (broken) and
the ammeter placed in series with the circuit

Handout 7 Week 7
Pg 67
E.2
circuit connection.
Ohmmeter is used when there is no current flowing in the circuit.
When using an ohmmeter:
 isolate the component or circuit section that requires measurement
to ensure a correct reading occurs
 avoid touching the metal probes of the ohmmeter as this may lead
to a false reading.
Warning
Failure to disconnect or isolate the component being measured from the
power supply will cause damage to the ohmmeter.

Handout 7 Week 7
Pg 68
E.2
circuit connection.
2.3.1 ELECTRICAL SYMBOLS
Standard symbols
These symbols are used so that everyone worldwide can understand
a circuit diagram when they see it.
Some are shown below.

Handout 7 Week 7
Pg 69
E.2
circuit connection.
2.3.2 CIRCUIT DIAGRAM
The circuit shown can be represented by the circuit diagram.
PICTORIAL CIRCUIT DIAGRAM CIRCUIT DIAGRAM
Circuit diagrams are usually drawn with straight lines at right angles to
each other.

Assignment 3 Week 7
Pg 71
E.2
circuit connection.
Q1 Draw the flowing circuit diagram show below. Give an explanation for each.
ANSWER
ANSWER

Handout 8 Week 8
Pg 73
E.2
2.4.0 State Ohm’s law.
2.4.1 OHM’S LAW
Ohm’s Law states that
The current passing through a conductor is proportional to the voltage
over the resistance, provided temperature remains constant.
A graph of current (I) against voltage (V) is obtain
The equation below shows the relationship between voltage, current and
resistance:
Potential difference (volt, V) = Current (ampere, A) × Resistance (ohm, Ω)
V = IR

Handout 8 Week 8
Pg 74
E.2
2.4.2 OHM’S LAW TRIANGLE
Transposing the standard Ohms Law equation above will give us the
following combinations of the same equation:

Assignment 4 Week 8
Pg 76
E.2
Q1 (a) State Ohm’s law.
(b) Sketch the graph of ohm’s law.
Q2 Write the formula for ohm’s law
Use voltage triangle to make to find I and V
ANSWER
ANSWER
ANSWER

Handout 9 Week 9
Pg 78
E.2
2.5.0 Demonstrate the application of Ohm’s law.
2.5.1 USING OHM’S LAW EQUATION
Find Voltage
If you know current and resistance, you can find voltage from V = I R.
For example, if the current I = 0.2 A and the resistance R = 1000 ohms,
then
Find Current
If you know voltage and resistance, you can use algebra to change
the equation to I = V / R to find the current. For example, if V = 110 V
and R = 22000 ohms, then
Find resistance
If you know voltage and current, you can use algebra to change the
equation to R = V / I to find the resistance. If V = 220 V and I = 5 A, then
ANSWER
V = IR
V = 0.2 A x 1000 Ω = 200 V
ANSWER
I = V/R
I = 110 V / 22000 Ω = 0.005 A
ANSWER
R = V/I
R = 220 V / 5 A = 44 Ω

Assignment 5 Week 9
Pg 80
E.2
Q1 An alarm clock draws 0.5 A of current when connected to a 120 volt circuit.
Calculate its resistance.
Q2 A circuit contains a 1.5 volt battery and a bulb with a resistance of 3 ohms.
Calculate the current.
Q3 How much voltage would be necessary to generate 10 amps of current in a
circuit that has 5 ohms of resistance?
Q4 A subwoofer needs a household voltage of 110 V to push a current of 5.5
A through its coil. What is the resistance of the subwoofer?
ANSWER
ANSWER
ANSWER
ANSWER

Assignment 5 Week 9
Pg 81
E.2
Q5 What happens to the current in a circuit if a 1.5-volt battery is removed and
is replaced by a 3-volt battery?
Q6 What happens to the current in a circuit if a 10Ω resistor is removed and
replaced by a 20Ω resistor?
ANSWER
ANSWER

Handout 10 Week 10
Pg 83
E.3 Demonstratethe knowledgeof simple circuit analysis
3.1.0 State Kirchhoff’s laws
3.1.1 KIRCHOFF’S LAWS
Kirchoff’s Law have two laws:-
1. Kirchoff’s Current Law (KCL)
States that
Water Analogy
Total current entering a point in circuit is equal total current
leaving that point in the circuit.
Water entering at point A = Water leaving at point B, C and D

Handout 10 Week 10
Pg 84
For Example
Determine IX shown in the
diagram.
0.2 + IX = 0.3 + 0.15 A
IX = 0.3 + 0.15 - 0.2
IX = 0.25 A
I1 = I2 + I3 + I4
Current entering = Current leaving

Handout 10 Week 10
Pg 85
2. Kirchoff’s Voltage Law (KVL)
States that
Sum of all voltage drop around the loop is equal to zero.
Consider the circuit diagrams below.
Pictorial circuit diagram Circuit diagram

Handout 10 Week 10
Pg 86
For Example
Use KVL to show that
Sum of all voltage drop around the loop is equal to zero.

Assignment 1 Week 10
Pg 88
Q1 State and explain Kirchoff’s current law.
Q2 State and explain Kirchoff’s voltage law.
ANSWER
ANSWER

Handout 11 Week 11
Pg 90
3.2.0 Demonstrate the knowledge of Kirchhoff’s laws.
3.2.1 GETTING MORE COMPLEX (KVL)
The Rules - Cells

Handout 11 Week 11
Pg 91
3.2.0 Demonstrate the knowledge of Kirchhoff’s laws
The Rules - Components
Putting it altogether
For Example
Working anticlockwise around the loop ABCDA

Handout 11 Week 11
Pg 92
Now try other direction
Working anticlockwise around the loop BADCB
Try this
BA = -15 V
DC = - 5 V - (4x3) V
CB = + (11x2) V
SO:
- 15 + 5 - 12 + 22 = 0
ANSWER
Workinganticlowisearound
the loopABCDA

Pg 94
Q1 Determine the currents IAB and Ix by using KCL in the figure shown below.
Q2 Determine the value of current flowing between A and B, and the value of
I3.
ANSWER
KCL at pointA
IAB= 0.5 – 0.3
IAB= 0.2 A
KCL at pointB
IAB= 0.1 + Ix
0.2 = 0.1 + Ix
Ix = 0.2 – 0.1 = 0.1 A
ANSWER

Pg 95
Q3 Determine the value I1 and R1 using KCL and KVL in the figure shown
below.
Q4 Determine the value of voltage.
ANSWER
Workingclockwise aroundthe loop
ABCDA
ANSWER
Workingclockwise aroundthe loop
ABCDA

Handout 12 Week 12
Pg 97
3.3.0 Draw and understand simple D.C. circuits
3.3.1 DRAWING CIRCUIT DIAGRAMS
Circuit diagrams show how circuit components are connected together.
Each component is represented by a symbol and a few are shown
below.
Steps to draw circuit diagrams:-
 Use the correct symbol for each component.
 Draw wires as straight lines (use a ruler).
 Put a 'blob' ( ) at junctions.
 Label components such as resistors and capacitors with their
values.
 The positive (+) supply should be at the top and the negative (-)
supply at the bottom. The negative supply is usually labelled 0V,
zero volts.
For Example

Handout 12 Week 12
Pg 98
NOTE
The standard wire crossover wire symbols used for circuit diagram.
Old style
Recommended style

Handout 12 Week 12
Pg 99
3.3.2 UNDESTANDING D.C. CIRCUITS
Below shows the difference between an incomplete circuit and complete
circuit.
The bulb will only light if there is a battery and a complete circuit.
Draw the circuit diagram for the pictorial circuit below.

Handout 12 Week 12
Pg 100
3.3.3 SERIES AND PARALLEL CIRCUITS
The components in a circuit are joined by wires.
 if there are no branches then it's a series circuit
 if there are branches it's a parallel circuit
Series circuit
A series circuit has a single circuit or pathway. IT may have one or more
power sources, and one or more loads, but only ONE pathway.
Below shows two lamps connected in series. Draw a circuit diagram for the
pictorial circuit.
Why each lamp has the same brightness?
Adding more light bulbs increase the resistance (less current) & dims all
the bulbs equally.

Handout 12 Week 12
Pg 101
What if a lamp breaks or a component is disconnected?
Parallel circuit
Parallel circuits have more than one pathway. Current leaving the power
source may follow 2 or more pathways before returning to the source.
Below shows two lamps connected in series. Draw a circuit diagram for
the pictorial circuit.
The circuit is said to be broken and all
the components stop working.
The circuit is incomplete.

Handout 12 Week 12
Pg 102
Why the bulbs in parallel bur more brightly than the same number of
bulbs in series.
The more pathways, the less the resistance, the greater the current.
Parallel circuits provide the same voltage for each load,
What if a lamp breaks or a component is disconnected from one
parallel wire?
The circuit is said to be broken and
all the components keep working.
Parallel circuits are useful in homes
or other places where one load
needs to be turned on while another
load is turned off.

Pg 104
Q1 Draw the circuit diagram of the following pictorial circuit diagram
below.
(a)
(b)
ANSWER
ANSWER

Pg 105
Q2 Draw the circuit diagram of the pictorial circuit diagram below.
Explain the connection.
ANSWER
EXPLANATION

Pg 106
Q3 Draw the circuit diagram of the pictorial circuit diagram below.
Explain its connection.
ANSWER
EXPLANATION

Handout 13 Week 13
Pg 108
3.4.0 Understand series and parallel resistor connections
3.4.1 RESISTOR IN SERIES AND PARALLEL
In this section we deal with the mathematics of more than one resistor in a
series or parallel circuit.
How to calculate total resistors connected in series?
Below shows two resistors connected in series with a battery.
Total Resistance, RT
RT = R1 + R2 + ... Rn
In a series circuit
 SAME CURRENT (I)
 DIFFERENT VOLTAGE (V)
Total IENTERING = Total ILEAVING
Rn = R1 + R2
V = V1 + V2
Therefore
V = IR = IR1 + IR2
Where R is the effective series resistance of the two resistors.

Handout 13 Week 13
Pg 109
How to calculate total resistors connected in parallel?
Below shows two resistors connected in parallel with a battery.
In a series circuit
 SAME VOLTAGE (V)
 DIFFERENT CURRENT (I)
V = V1 = V2
RT = R1R2/(R1+ R2 )
I = I1 + I2
Since
V = I1R1 = I2R2, I = V/R = V/R1 + V/R
Where R is the effective series resistance of the two resistors.
Total Resistance, RT
𝟏
𝐑𝐓
=
𝟏
𝐑𝟏
+
𝟏
𝐑𝟐
+ ⋯
𝟏
𝐑𝐧
𝐑𝐓 =
𝐑𝟏𝐑𝟐
𝐑𝟏 + 𝐑𝟐

Handout 13 Week 13
Pg 110
3.4.2 POWER DISSIPATED IN RESISTORS
When a current flows through a resistor, a voltage drop across it dissipates
electrical power. This electrical power is converted into heat energy
By definition,
Power is rate of energy converted.
Electrical Power depends on both voltage and current.
For Example
The diagram below will explain why bulbs in series are dimmer because of
changes to both current and voltage.
𝐏𝐎𝐖𝐄𝐑 =
𝐄𝐍𝐄𝐑𝐆𝐘
𝐓𝐈𝐌𝐄
SI UNIT: Watt (W)
1W = 1J/1S

Handout 13 Week 13
Pg 111
Explanation
Brightness depends on power. And power depends on both current and
voltage.
To control brightness, a variable resistance is connected in series.
By varying the resistance from LOW to HIGH
 BRIGHTNESS CHANGES
see next page
Two bulbs in series
Ohm’s Law V = IR
Current SAME
Resistance HIGH
Voltage LOW P.D =
1
2
V
Bulbs DIMMER
One bulb
Ohm’s Law V = IR
Current SAME
Resistance LOW
Voltage HIGHER
Bulbs BRIGHTER

Handout 13 Week 13
Pg 112
Power dissipated depends also on resistance, R of the wire.
By definition,
Electrical Power, P = IV and ohm’s law states that V = IR
Therefore using
V = IR
Power is dissipated as heat.
P = IV
when, V = IR , P = I2R
I = V/R , P = V2/R

Pg 114
Q1 Calculate the total in each of the following combinations resistors.
a)
b)
c)
d)
ANSWER
ANSWER
ANSWER
ANSWER

Pg 115
Q2 For each of the following circuits complete the readings on the voltmeters.
a)
b)
c)
9V
3V
ANSWER
ANSWER
ANSWER

Pg 116
Q3 For the circuit below, calculate the power dissipated in the resistor.
Q4 For the circuit below, calculate the value of the resistor.
ANSWER
ANSWER

Handout 14 Week 14
Pg 118
E.4 Demonstratethe knowledgeof AC current
4.1.0 The definition of alternating current is given.
4.1.1 ALTERNATING CURRENT (AC)
AC current is a sinusoidal waveform or simply a sine wave. The current
reverses polarity over time.
The diagram below show the production of sine wave.
AC Sources
A simplified AC generator is connected with an oscilloscope.
AC Generator Simplified Model

Handout 15 Week 14
Pg 120
4.2.0 Demonstrate the knowledge of circuit representation of alternating current
4.2.1 CIRCUIT REPRESANTATION OF AN AC CURRENT
Symbol for an AC source
The diagram below shows an AC source connected to an electrical load.
Electrical Load
The term ‘load’ is an electrical component that consumes electric power.
The load will convert electricity into light, heat or mechanical motion.
Examples of loads are light bulb, resistors or motor.
Similar discussion can be applied in alternating current circuits using
resistive, capacitive and inductive elements.
The symbol for an AC source is represented
by a sine wave.
AC always changes direction of current and
voltage over a time.

Handout 16 Week 14
Pg 122
4.3.0 Draw and describe sinusoidal waveform
4.3.1 ESSENTIAL FEATURES OF A SINUSOIDAL WAVEFORM
Below shows the characteristics of a sine wave.
An AC waveform is usually describe as the graph of :-
 Voltage (V/V) against Time (t/s)
 Current (I/A) against Time (t/s)
DEFINITIONS
A sinusoidal AC waveform
1 = peak, also amplitude,
2 = peak-to-peak,
3 = effective value,
4 = Period
1. Waveform - Graphical representation of a wave
2. Peak Value - Max value from its zero reference level
3. Peak to Peak Value - Measurement from one peak to the other.
4. Effect Value/RMS - Root mean square value, which is the equivalent
heating effect of direct current.
5. Period (T) - Time taken to complete one cycle of a waveform.
Measured in seconds, milliseconds or microseconds.
6. Frequency(f) - Number of cycles of waveforms which in one second of
time. Measured in hertz (Hz). f = 1/T.

Pg 124
Q1 a) What does AC stands for?
b) Define AC Current?
c) Draw the symbol for AC.
Q2 a) Draw a simple AC generator circuit diagram.
b) Draw a simple DC generator circuit diagram.

Pg 125
Q3 a) What is an electrical load?
b) Give four example of an electrical load
Q4 Draw the following circuit diagram connected with an AC source.
a) Resistive load
Capacitive loadb)
c) Inductive load
1.
2.
3.
4.

Pg 126
Q5 a) The mains supply is alternating current (ac).
What does this means?
b) The AC mains has a supply of 230V/50Hz.
What does this means?
c) Sketch the voltage-time graph showing the various properties of
the AC main supply of 230V/50Hz.
Where,
This means that the current from a mains supply constantly changes
direction in a circuit.
Mains electricity is the term used to refer to the electricity supply from
power stations to households.
Mains voltage or line voltage is 230V.
50Hz is the frequency of the a.c. supply is 50 cycles per second.
VP VRMS VP-P
T
VP - Peak voltage
VRMS - Root mean square value of voltage
VP-P - Peak to peak voltage
T - Period, T = 1/f = 1/50 = 20ms

Handout 17 Week 15
Pg 128
E.5 Demonstratethe basic understandingof three phase AC
5.1.0 Demonstrate the difference between single and three phase current.
5.1.1 SINGLE PHASE POWER
Single Phase power is a two wire Alternating Current (AC) power circuit.
It consists of :-
1. One power wire, i.e. the line wire or hot wire or live wire
2. One neutral wire
Neutral is a circuit conductor that normally carries current back to the
source, and is connected to ground (earth) at the main electrical panel.
Power flows between the power wire (through the load) and the neutral
wire.
Single phase powers are mostly used in residential areas, to power their
lights, TV, household appliances, pump, water heater ...ect.
In Seychelles, 230V is the standard single phase voltage with one 230V
power wire and one neutral wire.
Below shows a circuit diagram of a single phase supply.

Handout 17 Week 15
Pg 129
E.5 Demonstratethe basic understandingof three AC
5.1.2 STANDARD SINGLE PHASE POWER PLUGS AND ADAPTERS
A device that lets you insert a plug into a different socket is an adapter.
There are many different plugs in the world.
1. The "American" plug, with two vertical pins
2. The "European" plug, with two round pins
3. The "British" plug, with three rectangular pins
Seychelles uses the ‘British plug’ – 3 pin plug, i.e. Live, Neutral and Earth
wires connections.
Plugs types around the world
Universal AC adapter plug
The Universal Adapter Plug allows you to
plug your small appliance or computer
into outlets around the world. It can
modify electrical outlet, does not change
the voltage, and supports universal
voltage 110V-240V.

Handout 17 Week 15
Pg 130
5.1.3 WIRING OF A 3-PLUG DIAGRAM
Colour code for 3 core wire cable
E

Handout 17 Week 15
Pg 131
5.1.4 THREE PHASE POWER
Three-phase electric power is a 3-wire alternating current.
It consists of :-
1. Three wire, i.e. 3 power line
2. One neutral wire
Below shows a simple diagram of a three phase generator.
Three Phase supply is generated when three similar coils are placed
120° apart. An E.m.f. is induced when rotated within the magnetic field.

Handout 17 Week 15
Pg 132
5.1.5 BS COLOUR CODE FOR THREE PHASE WIRE
Seychelles wiring system is according to British Standard (BS) Code.
Three phase wires have changed from old to new colour codes.
Old colour code: RED, YELLOW and BLUE, BLACK for neutral (RYB).
New colour code: BROWN, BLACK and GREY, BLUE for neutral (BBG).
A 3-phrase 4-wire supply carrying 240V in each wire
4-wire supplies are normally used to distribute domestic supplies since
they can provide an earthed neutral.
The three phase wires together give a 3-phase 3-wire supply suitable for
heavy machinery such as 3-phase motors.
Three single-phase 240V supplies are available between each phase
line and the neutral wire.
The three phase single-phase 415V supplies are available between any
of the three phases.

Pg 134
Q1 Figure below shows a 3 – Pin Plug
a) What does the following letters stands for?
E
L
N
b) What is the colour for E, L and N
E
L
N
c) What is the function of the fuse?
What is the function of the cable grip?d)

Pg 135
Q2 Draw a single phase circuit diagram
Showing the importance of earth wire connected to ground.
Q3 What are the differences between a single phase power and three
phase power?

Handout 18 Week 16
Pg 137
5.2.0 Demonstrate the knowledge of major applications in three phase current in the context of
Mechanical engineering
5.2.1 APPLICATIONS OF THREE PHASE CURRENT
In Mechanical Engineering three phase current have various applications.
Some of the major applications are describe below:-
1. Manufacturing
2. Industrial Maintenance
Arc Welding Milling Machine Lathe Machine
Air Compressor Electric Motor
Pump
3 Phase Generator

Pg 139
5.2.0 Demonstrate the knowledge of major applications in three phase current in the context of
Mechanical engineering
Q1 What are the major industries in Seychelles related in Mechanical
Engineering?
Q2 Give some applications of three phase current in the context of
mechanical engineering.

Handout 19 Week 17
Pg 141
5.3.0 Describe wiring arrangement related to three phase current supply
5.3.1 THREE PHASE WIRRING ARRANGEMENT
In three phase circuit, connections can be given in two types:
1. STAR OR WYE CONNECTION
2. DELTAOR MESH CONNECTION

Handout 19 Week 17
Pg 142
5.3.2 THREE PHASE MOTOR CONNECTION
For both star and delta,
The motor can use both 230V and 415V.
The winding is delta connected at 230 V and if the main voltage is 400 V,
the star connection is used.
When changing the main voltage it is important to remember that for the
same power rating the rated motor current will change depending on the
voltage level.
The method for connecting the motor to the terminal blocks for star or delta
connection is shown in the picture below.
For Delta Connection
For Star Connection

Handout 19 Week 17
Pg 143
For star delta,
The motor connection must have 6 terminals at induction motor
U1,U2,V1,V2,W1,W3
For Star Connection
Consider the diagram below
For Delta Connection
Consider the diagram below

Pg 145
Q1 Draw a circuit diagram star connected 3ϕ supply feeding a balanced
star connected load.
Q2 Draw a circuit diagram delta connected 3ϕ supply feeding a balanced
delta connected load.

Pg 146
Q3 Draw a diagram for a 3 phase generator connecting a 3 phase load.
Q4 Explain a three phase 4 wire wye system?

Pg 147
5.3.0 Describe wiring arrangement related to three phase current supply.
Q5 Explain the star motor connection?
Q6 Explain the delta motor connection?

Handout 20
Pg 149
E.6
Demonstratethe basic understandingand use of basic tools and
instruments used in applied electricity
6.1.0 Demonstrate the basic circuit preparation components and tools.
6.1.1 ELECTRICAL SPECIFIC TOOLS
In Mechanical Engineering, electrical tools are needed to perform a
particular job in maintenance section. Proper use of tools is needed to
ensure safety.
Basic electrical hand tools
1. ELECTRICAL SCREWDRIVERS
FLAT SCREWDRIVER
PHILIPS SCREW DRIVER
Properties: Insulated, 230V/415V
Function: Use to drive screws with a
single slot heads.
Properties: Insulated, 230V/415V
Function: Use to drive screws with
cross slot heads.

Handout 20
Pg 150
E.6
2. ELECTRICAL PLIERS
LONG NOSE PLIERS
Properties: Insulated, cutting and
holding
Function: Use to cut and hold wires.
Properties: Insulated, wire cutter –
blades
Function: Use to cut fine, medium and
big wires and cables.
CUTTING PLIERS
CUTTING PLIERS
Properties: Insulated, gripping, holding
and cutting
Function: Use to grip, cut and hold
wires.

Handout 20
Pg 151
E.6
3. WIRE REMOVALS
4. ELECTRICAL HAMMER
Properties: Insulated, wire cutting
teeth – various sizes
Function: Use to cut the insulation off
of the wire.
WIRE STRIPPER
CABLE KNIFE
Properties: Insulated, insulation
removal
Function: Use to remove the insulation
of cables in low or high voltage.
Properties: Insulated, diving or pulling
nails
Function: Use for pounding nails into,
or extracting nails from.
CLAW HAMMER

Handout 20
Pg 152
E.6
6.1.2 ELECTRICAL LINE TESTER
Basic understanding of use of Electrical line tester
Function
The Line Tester is tool used to identify the Phase or Live Wire.
Working of the line tester
Precautions
Main parts of the line
tester
 The Line Tester or Neon
Screwdriver is tools specified for
electrical works.
 Screwdriver in special case.
 The main parts are shown on the
left hand side.
The user is required to be on the floor
while using the tester so that he can serve
as ground when current flows.
In order to test the live wire, the user’s
body must be in contact with the metal cap on the top of the screwdriver
when the tester is put in contact with the wire. This completes a genuine
electrical circuit and the bulb will light up once the tester senses voltage.
Ensure that the tester is working properly. Ensure that the tester is not
broken. Don’t touches the open wire even tester shows absence of phase
or hot supply. Never try to test the presence of phase or hot wire of any
high voltage supply source the flow of current can be lethal.

Handout 20
Pg 153
E.6
6.1.3 ELECTRICAL WIRE CONNECTORS
Types of electrical wire connectors
There are different types of wire connectors. Some are shown below.
Examples: Showing Terminal block connection
BLOCK TERMINALS
TWIST WIRE TYPES

Handout 20
Pg 154
E.6
6.1.4 APPLICATIONS OF INSULATION TAPES
Insulation tape / Electrical tape
It is a type of pressure-sensitive tape used to insulate electrical wires and
other materials that conduct electricity.
It is made up of many plastics.
Standard Insulation tape
A selection of color-coded electrical tapes.
Electricians generally use only black tape for insulation purposes. The
other colors are used to indicate the voltage level and phase of the wire.
TAPE COLOUR INTERNATIONAL USAGE
BLACK - Low voltage, phase B
RED - Sheath, 415 V 3 phase
BLUE - Low voltage, neutral
Sheath, 230 V
YELLOW/GREEN - Earth
BROWN - Low voltage, phase A
GREY - Low voltage, phase C

Handout 20
Pg 155
E.6
Common Example
Electrical tape is used
 for insulating electrical wires to prevent short circuits and
electrocution
 to connect feeder cables to motor leads
 on bus bar connections
 for low- to high-voltage electrical connections

Handout 20
Pg 156
E.6
6.1.5 EDGE PREPARATION TOOLS AND METHODS
Task 1: Removing insulation of a wire with different tools.
Tools
1. Combination plier
2. Side cutting plier
3. Long nose plier
4. Wire stripper
5. Electrician plier
Materials: solid and stranded copper wire of different sizes
Tasks Pictures of tasks
1. Skin a wire a using an
electrician’s knife, about 1 to
1
1
2
inches long.
2. Skin a wire a using a
combination wire and side
cutting plier, about 1 to 11/2
inches long.
3. Remove insulators using wire
stripper, about 1 to 11/2
inches long.

Handout 20
Pg 157
E.6
Task 2: Wirring of a 3-pins plug with different tools.
Tools
1. Combination plier
2. Side cutting plier
3. Long nose plier
4. Wire stripper
5. Electrician plier
6. Philips screw driver
Materials: 3 core – 1 mm stranded copper cable
1. Strip the ends of the three
wires inside the electrical cord
for about 1 to 1
1
2
inches long,
by cutting away the plastic
insulation, with a side cutting
or wire stripper.
2. Gently twist the strands of
copper wire with your fingers
until each strand is tight. Fold
over the twisted strands.
3. Remove the plug cover by
with a Philips screw driver in
the center of the plug, on the
side with the three pins poking
out.

Handout 20
Pg 158
E.6
4. Unscrew the little screws on
each of the plug's pins.
5. Insert the twisted copper wires
into the holes in the pins. The
brown wire is inserted into the
right pin (the pin is marked
with a brown spot or the letter
L)
6. Tighten the little screw on
each of the plug's pins.
7. Make sure the electrical cord
is firmly gripped by the
arrestor clips. The green and
yellow wire must always be
inserted into the top pin. The
blue wire is inserted into the
left pin (the pin is marked with
a blue spot or the letter N).

Handout 20
Pg 159
E.6
8. Put the back of the plug back
on once all the wires are in
and tight, and all the screws
are securely done up.

Handout 20
Pg 160
E.6
6.1.6 STUDENT PROJECT WORK
Project around: Making an extension cable.
Objective:
a. Demonstrate how to make an extension cord.
b. Observe safety measures while doing the project.
Sketch / drawing
Materials needed:
Name 1.
2.
3.
Batch …..
Date starting …../……/2017
Date starting …../……/2017
RESULTS
………

Handout 20
Pg 161
E.6
Tools:
Procedure:

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