Chapter 1: Introduction to Principles of Electric and Electronics

PRINCIPLES OF ELECTRIC &
ELECTRONICS
BEKG 1123
Semester 2, 2015/2016
9/19/2017
1

9/19/2017 2
Name : IR MOHAMMAD `AFIF BIN KASNO
Phone : 019-6481883
Email : mohammad.afif@utem.edu.my
Lecture/ Tutorial:
1 BEKM 2 : Tuesday, 8am – 10am (BK13)
Wednesday, 9am – 11am (BK1)

 ULEARN:
BEKG1123 PRINCIPLES OF ELECTRIC AND ELECTRONICS
(1BEKM S2)
Chapter 1 5

INTRODUCTION
1.1 Basic Electric System
1.2 Electrical Circuits
1.3 Electrical Charge
1.4 Electromotive Force (emf) and Potential Difference
1.5 Voltage and Current
1.6 Systems of Units: SI units in Electrical
1.7 Electrical Measurement & Instruments
1.8 Symbols of Electrical Sources & Components
1.9 Circuit Elements: Passive & Active
Chapter 2 : Direct Current (DC) Circuits
BEKG 1123
Principles of Electric and Electronics 6

At the end of this chapter, students should be able to:
 Describe basic electrical systems and the concept of electrical
charge
 Differentiate between EMF and Potential Differential
 Understand the systems of units
 Describe electrical measurement & instruments and the
symbol s of electrical sources & components
 Identify the circuit elements
Chapter 1 7

Fig. 1 Electrical system
Chapter 1 8
1.1 BASIC ELECTRIC SYSTEM
Source Control Load
Transmission
System
Electric system – deals with communication and transfer energy from
one point to another.
Basic electrical system consists of 4 elements: Source, Control, Load
and Transmission System (as shown in Fig. 1)
Transmission
System

ELECTRICAL SYSTEM CONTD.
 Source - Provide electrical energy to electrical system (i.e DC
or AC source). Can be obtain from battery, generator or socket
outlet.
 Control - Control the flow of electrical energy (i.e switch).
Permits the energy to flow or else interrupts the flow.
 Load - Absorb the electrical energy and perform a given
task/purpose/work. Most domestic electrical equipment
constitutes loads (i.e motor)
 Transmission system - Conduct and transfer electrical energy
from source to load (i.e insulated wire)
Chapter 1 9

Fig. 2 Torch Light system
Chapter 1 10
Example
ELECTRICAL SYSTEM contd.
Physical configuration Circuit diagram

Fig.3 Headlight system
Chapter 1 11
Example
ELECTRICAL SYSTEM contd.
Physical configuration Circuit diagram
Switch
Battery
Wires
Headlamps Voltage source
Switch
Conductors/Wires
Resistance

Chapter 1 12
1.2 ELECTRICAL CIRCUITS
Electrical Circuit – consists of various types of circuit elements connected
in closed paths by conductor (refer Figure 1.4).
Voltage sources create forces that cause charge to flow through the conductors
and other circuit elements, so energy transferred between the circuit elements.
**Circuit elements – resistances,
inductances, capacitances and
voltage/current sources.
Fig. 4 Electrical circuit

Chapter 1 13
1.3 ELECTRICAL CHARGE
Electrical Charge – also known electricity.
The elementary physics that all matter is made of atoms and each
atoms consists of electrons, protons and neutrons.

Chapter 1 14
ELECTRIC CHARGE contd.
 The presence of equal numbers of protons and electrons leaves an
atom neutrally charged.
 Some atoms hold their electrons loosely (when force is applied)
especially electrons that are located at valence shell (outermost
shell).

 The loose electrons (free electron) can be transferred into another
atoms.
When an electron escapes from the atom – becomes positive ion.
When atom acquire an electron – becomes negative ion.
Chapter 1 15

A substance/materials that excess of electrons (negative ion) is said to have
negative charge.
Materials with deficiency of electrons (positive ion) is said to have positive
charge.
Electrical charge – an electrical property of matter that exists because of an
excess or defiance of electrons.
Charges can be measured in coulomb
1 Coulomb (C) = 6.24 x 1018 electrons
1 electron = 1.602 x 10 -19 C
Materials with charges of opposite polarity attracted.
Materials with charges of same polarity are repelled.
Chapter 1 16

Chapter 1 17
1.4 ELECTROMOTIVE FORCE (emf)
VS. POTENTIAL DIFFERENCE
emf Potential difference
Emf is the electrical
potential difference
provided by an energy
source like battery.
Varying magnetic fields also
can generate an emf
according to the Faraday’s
law.
Although EMF is also a
voltage and measured in
Volts (V), it is all about the
generation of a potential
difference.
Potential is a function of the
location, and potential
difference between point A
and point B is calculated by
subtracting the potential of
A from potential of B.
In an electric field, it is the
amount work to be done to
move a unit charge (+1
Coulomb) from B to A.
Electric potential difference
is measured in V (Volts). In
an electrical circuit, current
flows from the higher
potential to lower potential.

Chapter 1 18
So the important differences between emf and potential difference
are:
1. The term ‘potential difference’ is used in all energy fields (electric,
magnetic, gravitational), and ‘emf’ is only used in electric circuits.
2. Emf is the electrical potential difference generated by a source like
battery or generator.
3. We can measure potential difference between any two points, but
emf exists only between the two ends of a source.
4. Sum of ‘potential drops’ around a circuit is equal to total emf
according to Kirchhoff’s second law.

Chapter 1 19
1.5 VOLTAGE AND CURRENT

The force (pressure) that causes
current to flow
When the faucet (switch) is off, is there any pressure (voltage)?
YES – Pressure (voltage) is pushing against the pipe, tank, and
the faucet.
When the faucet (switch) is on, is there any pressure (voltage)?
YES – Pressure (voltage) pushes flow (current) through the
system.
Tank (Battery) Faucet (Switch)
Pipe (Wiring)
- measured in VOLTS (V)

The battery provides voltage that will push
current through the bulb when the switch is on.
off on
off on

VOLTAGE cont.
 To move an electron in a conductor in a particular direction
requires some work or energy transfer.
 This work can be performed by an external force or called as
electromotive force (emf).
 This emf also known as potential difference or voltage.
 Voltage (V) is the energy required to move a unit charge
through an element, measured in volts (V).
 Voltage is a measurement of potential difference between two
points.
Chapter 1 22

Chapter 1 23
 Vab – voltage between point a and b
 It is the energy (or work) needed to move a unit charge from a to b.
 plus (+) and minus (-) signs – voltage polarity or reference direction.
VOLTAGE cont.

 Voltage (V) is defined as energy/work per unit charge
V = W/Q
where V is voltage in volts(V), W is energy in joules (J) and Q
is charge in coulombs (C).
 A voltage source is an energy source that provides electrical
energy or voltage.
 Two types of voltage sources:
 dc voltage – a constant voltage with time. i.e. battery.
 ac voltage – a voltage that varies with time. i.e. electric
generator, socket outlet.
Chapter 1 24
VOLTAGE cont.

The flow of electric charge
When the faucet (switch) is off,
is there any flow (current)?
NO
When the faucet (switch) is on,
is there any flow (current)?
YES
Tank (Battery) Faucet (Switch)
Pipe (Wiring)
- measured in AMPERES (A)

When the switch is off, there is no current.
When the switch is on, there is current.
off on
off on

CURRENT contd.
 Voltage provides energy to electron, allowing them to move through a
circuit.
 This movement of electrons is the current, which result in work being
done in an electrical circuit.
 Consider the following:
 negative charges move from the negative terminal of battery towards
the positive terminal.
Chapter 1 27

 Flow of current in metallic conductors is due to movement of
electrons.
 However, it is universally accepted that current is the net flow of
positive charges.
 There are two accepted conventions for the direction of electrical
current:
1. Electron flow direction – current is out of the negative
terminal of a voltage source, through the circuit and into the
positive terminal of the source.
2. Conventional current direction – current is out of the
positive terminal of a voltage source, through the circuit and
into the negative terminal of the source.
Chapter 1 28
CURRENT contd.
Conventional
Current
Electron
Flow

 The direction that the current flows does not affect what the
current is doing; thus, it doesn’t make any difference which
convention is used as long as you are consistent.
 Both Conventional Current and Electron Flow are used. In
general, the science disciplines use Electron Flow, whereas
the engineering disciplines use Conventional Current.
 Since this is an engineering course, we will use
Conventional Current .
Electron
Flow
Conventional
Current

Chapter 1 30
 Electric current – the time rate of change of charge, measured in
amperes (A).
I = Q / t
where I is current in amperes(A), Q is charge in coulombs (C)
and t is time in seconds.
 Generally, have two types of current:
 direct current (dc) – a current that remains constant with time.
 alternating current (ac) – a current that varies with time.
CURRENT contd.

 Basic SI (International System of Units) units:
Quantity Unit Symbol
Charge (q) coulomb C
Energy (E) joule J
Power (P) watt W
Voltage (V) volt V
Current (I) ampere A
Resistance (R) ohm Ω
Induction (L) Henry H
Capacitance (C) farad F
Chapter 1 31
1.6 SYSTEMS OF UNITS

Chapter 1 32
Unit Name Unit Symbol
Volt
• Volt is the electrical unit of voltage.
One volt is the energy of 1 joule that is
consumed when electric charge of 1
coulomb flows in the circuit.
(V)
1V = 1J / 1C
Ampere
• Ampere is the electrical unit of
electrical current. It measures the
amount of electrical charge that flows
in an electrical circuit per 1 second.
(A)
1A = 1C / 1s
Ohm
• Ohm is the electrical unit of
resistance.
(Ω)
1Ω = 1V / 1A
Watt
• Watt is the electrical unit of electric
power. It measures the rate of
consumed energy.
(W)
1W = 1J / 1s
1W = 1V · 1A
Farad
• Farad is the unit of capacitance. It
represents the amount of electric
charge in coulombs that is stored per
1 volt.
(F)
1F = 1C / 1V
Henry
• Henry is the unit of inductance.
(H)
1H = 1Wb / 1A

The SI prefixes:
Power of 10 Prefix Symbol
+18 Exa E
+15 Peta P
+12 Tera T
+9 Giga G
+6 mega M
+3 kilo k
+2 hecto h
+1 deka D
- 1 deci d
- 2 centi c
- 3 mili m
- 6 micro µ
- 9 nano n
- 12 pico p
- 15 femto f
- 18 atto a
Chapter 1 33
SYSTEMS OF UNITS contd.

 Multimeter
Digital Multimeters (DMM)
Analog Multimeter
1.7 ELECTRICAL MEASUREMENT
INSTRUMENTS

Chapter 1: Introduction to Principles of Electric and Electronics

Most analog ammeters have a number of
possible settings for the maximum possible
current that can be measured; for example: 2 A,
200 mA, 20 mA, 2 mA.You should always start by
turning the setting to the highest possible rating
(for example, 2 A). If the ammeter reading is too
small from the selected scale, then you can
reduce the scale to get the reading. It is
important not to overshoot the maximum value
that can be read.
For example, if the current is about 75 mA, then
the ammeter would be set to the 200 mA scale
for the most accurate reading. Setting to the
20 mA scale would overload the ammeter and
most likely open its internal fuse.

 Error :The difference between the true value and the measured
value
• Accuracy :The degree to which a measured value represents the
true or accepted value of a quantity. A measurement is said to be
accurate if the error is small.
• Precision :The repeatability or consistency of a measurement

41
 Resolution
 The smallest increment of quantity that the meter can measure. The
smaller the increment, the better the resolution.
0.001V
0.01V

1.8
SYMBOLS
OF
ELECTRICAL
SOURCE
AND
COMPONENTS
Chapter 1 42
Symbol Component Name Meaning
SPST Toggle Switch Disconnects current when open
Earth Ground
Used for zero potential reference
and electrical shock protection.
Chassis Ground
Connected to the chassis of the
circuit
Resistor (IEEE) Resistor reduces the current flow.
Variable Resistor / Rheostat
(IEEE)
Adjustable resistor - has 2
terminals
Capacitor
Capacitor is used to store electric
charge. It acts as short circuit
with AC and open circuit with DC.
Battery Generates constant voltage
AC Voltage Source AC voltage source
Diode
Diode allows current flow in
one direction only (left to
right).

43
 Element – basic building block of a circuit or electrical
components of an electrical circuit.
 Electric circuit – an interconnection of electrical elements.
 Circuit analysis – process of determining voltages across (or
the currents through) the elements of the circuit.
 Two types of elements in electrical circuits:
Active elements
Passive elements
1.9 CIRCUIT ELEMENTS

44
 Passive components: Components
that do not supply voltage or
current.
 Examples
 Resistors
 Capacitors
 Inductor
 Transformer
Color bands
Resistance material
(carbon composition)
Insulation coating
Leads
Mica
Foil
Foil
Mica
Foil
Foil
Mica
Foil
Tantalum electrolytic
capacitor (polarized)
Mica capacitor_

 The components that have their own power source.
 Passive components are used in conjunction with active components to form an
electronic system.
 Examples
 Voltage and current sources
 Battery, Generator, Fuel cell
 Transistor
 Integrated Circuit (IC)

46
• Active elements – elements capable of generating
electrical energy i.e. voltage source & current source.
• Passive elements – elements not capable of
generating electrical energy i.e. resistor, capacitor and
inductors.
 Voltage & current source deliver power to the
electrical circuit.
 Two kinds of sources:
 Independent sources.
 Dependent sources.
CIRCUIT ELEMENTS contd.

Chapter 1 47
 Ideal independent source – an active elements that provides a
specified voltage or current that is completely independent of
other circuit elements.

Chapter 1 48
Ideal independent voltage source delivers to
the circuit whatever current is necessary to
maintain its terminal voltage.

Chapter 1 49
Ideal independent current source delivers to
the circuit whatever voltage is necessary to
maintain the designated current.

Chapter 1 50
 Ideal dependent (or controlled) source – an active
element in which the source quantity is controlled by
another voltage or current.
 Four types of dependent source:
 A voltage-controlled voltage source (VCVS)
 A current-controlled voltage source (CCVS)
 A voltage-controlled current source (VCCS)
 A current-controlled current source (CCCS)

51
 Consider the following:
 The CCVS is depends on i.
 Value = 10i V

Chapter 1: Introduction to Principles of Electric and Electronics

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