ESO 210/ESO203A
Introduction to Electrical Engineering
(Units 3-1-2-13)
(2014-15, First Semester)
Lecture-1
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Introduction to Electrical Engineering
(Units 3-1-2-13)
(2014-15, First Semester)
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Instructor: N K Verma (nishchal@iitk.ac.in)
Office: 107 ACES
Tel: 6524
Lecture: Monday, Wednesday and Friday (from 10am to 11am)
Lecture Venue: L-8
Tutorial: Thursday(from 10am to 11am)
Tutorial Venue: T203/T204/T205/T206
Lab: Monday and Wednesday (from 2pm to 5pm)
Lab Venue: WLE 313
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Syllabus:
• DC and AC sources, Concept of phasors, Single phase circuits, KCL and KVL, Thevenin
and Norton Theorems, Nodal and mesh equations, Y-Δ conversion, power calculations.
• Three phase circuits, Power calculation in three phase circuits.
• Magnetic Circuits, Mutually coupled circuits
• Transformers, Equivalent circuit and performance
• Direct Current Machines (DC Machines):
Constructional details, Separately excited and shunt excited DC motors/ generator, Series
DC motors, torque speed characteristics, Compound machines, Application of DC motors &
generators.
• Induction Machine (3-ph):
Constructional details, equivalent Circuit, Torque- speed characteristics, speed
control,starting and applications.
• Synchronous Machines:
Constructional details, Equivalent circuit, Generator and Motor operation, Power angle
characteristics.
• Single phase induction motors, Stepper motors and their control
• Principles of industrial power distribution
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Suggested readings/reference books
• Electrical Engineering Fundamentals, V. Del
Toro
• Engineering Circuit Analysis: Hayt, Kemmerly,
and Durbin
• Basic Electrical Engineering, Nagrath & Kothari.
• Principles of Electrical Machine and Power
Electronics, P.C. Sen.
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Distribution of Marks
• Mid –I 20 %
• Quiz
10 %
• Tutorial 10 %
• Lab
15 %
• Class performance 10%
• End Sem 35 %
Total
100 %
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Brief History of Electrical Engineering
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William Gilbert (1540-1603), English physician, founder of magnetic science.
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Charles A. Coulomb (1736-1806), French engineer and physicist, published the laws of electrostatics in seven
memories to the French Academy of Science between 1785 and 1791. His name is associated with the unit of
charge.
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James Watt (1736- 1819), English inventor, developed the steam engine. His name is used to represent the unit
of power.
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Alessandro Volta (1745-1827), Italian physicist, discovered the electrical pile. The unit of electrical potential
and the alternative name of this quantity (voltage) and named after him.
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Hans Christian Oersted (1777-1851), Danish physicist, discovered the connection between electricity and
magnetism in 1820. The unit of magnetic field strength, Oersted (Oe) is named after him.
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Ander Marie Ampere (1775-1836), French mathematician, chemist, and physicist, experimentally quantified
the relationship between electric current and the magnetic field. The unit of electrical current is named after him.
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Georg Simon Ohm (1789- 1854), Germen mathematician, investigated the relationship between voltage and
current and quantified the phenomenon of resistance. His name is used to represent the unit of resistance.
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Michael Faraday (1791-1867), English Experimenter, demonstrated electromagnetic induction in 1831. His
electric transformer and electromagnetic generator marked the beginning of the age of electric power. His name
is associated with the unit of capacitance.
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Brief History of Electrical Engineering
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Joseph Henry (1797-1878), U.S. physicist, discovered self induction around 1831, and his name been designated
to represent the unit of inductance.
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Carl Friedrich Gauss (1777-1855) , Germen mathematician, and Wilhelm Eduard Weber (1831-1891),
Germen physicist, published a treatise in 1831 describing the measurement of earth’s magnetic field. The gauss is a
unit of magnetic field strength, while the weber is the unit of magnetic flux.
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James Clerk Maxwell (1831-1879), Scottish physicist, discovered the electromagnetic theory of light and the
law of electrodynamics. The modern theory of electromagnetics is entirely founded upon Maxwell’s equations.
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Ernst Werner Siemens (1816-1892) and Wilhelm Siemens (1823-1883), Germen inventors and engineers,
contributed to the invention and development of electrical machine, as well as to perfecting electrical science. The
modern unit of conductance is named after them.
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Gustav Robert Kirchhoff (1824-1887), German Scientist, gave two fundamental laws of circuit analysis.
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Heinrich Rudolph Hertz (1857-1894), German scientist and experimenter, discovered the nature of
electromagnetic waves and published his findings in 1888. His name is associated with the unit of frequency.
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Nikola Tesla (1856-1943), Croatian inventor, Immigrated to the United Sates in 1884. He invented poly phase
electrical power systems and the induction motor and pioneered modern AC electrical power systems. His name is
used to represent the unit of magnetic flux density.
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Some Important Electrical Quantities
Charge:
Electric charge is a physical
property of matter which causes it to
experience a force when near other
electrically charged matter.
Classically, electric charge comes in
two types. These are
called positive and negative.
Two positively charged substances, or
objects, experience a mutual repulsive
force, as do two negatively charged
objects. Positively charged objects and
negatively charged objects experience
an attractive force. The SI unit of
electric charge is the coulomb (C).
Current:
Electric current means, depending
on the context, a flow of electric
charge (a phenomenon) or the rate of
flow of electric charge (a quantity).
This flowing electric charge is typically
carried by moving electrons, in
a conductor such as wire; in
an electrolyte, it is instead carried
by ions, and in a plasma by both.
The SI unit for measuring the rate of
flow of electric charge is the ampere,
which is charge flowing through some
surface at the rate of one coulomb per
second. Electric current is measured
using an ammeter.
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Some Important Electrical Quantities
Voltage:
Electric potential is the energy required to move a
unit electric charge to a particular place in a
static electric field.
Voltage can be measured by a voltmeter.
The unit of measurement is the volt.
The voltage between two ends of a path is the
total energy required to move a small electric
charge along that path, divided by the
magnitude of the charge.
Mathematically this is expressed as the line
integral of the electric field and the time rate of
change of magnetic field along that path.
Historically this quantity has also been called
"tension” and "pressure". Pressure is now
obsolete but tension is still used, for example
within the phrase "high tension" (HT) which is
commonly used in thermionic valve (vacuum
tube) based electronics.
Power:
Electric Power consumed is defined as the
multiplication of voltage deference in the
medium and current flowing though it.
The unit of power is watt
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Electrical Network: A combination of various electric elements
(Resistor, Inductor, Capacitor, Voltage source, Current source)
connected in any manner what so ever is called an electrical
network. We may classify circuit elements in two categories,
passive and active elements.
Passive Element: The element which receives energy (or
absorbs energy) and then either converts it into heat (R) or
store it in an electric (C) or magnetic (L ) field is called passive
element.
Active Element: The elements that supply energy to the circuit
is called active element. Examples of active elements include
voltage and current sources, generators, and electronic devices
that act as power supplies.
A transistor is an active circuit element, meaning that it can
amplify power of a signal. On the other hand, transformer is
not an active element because it does not amplify the power
level and power remains same both in primary and secondary
sides. Transformer is an example of passive element.
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Bilateral Element: Conduction of current in both directions in an
element (example: Resistance; Inductance; Capacitance) with same
magnitude is termed as bilateral element.
Unilateral Element: Conduction of current in one direction is
termed as unilateral (example: Diode, Transistor) element.
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Source of Electrical Energy:
There are two possible types of
Energy sources used
studies: a voltage
in network
source and a
current source (fig 1.1) and they are
represented as shown
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(a) Voltage Source
+
(b) Current Source
i(t)
(t)
-
(b)
(a)
Fig 1.1
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The
sources can again
be
classified as independent and
dependent types;
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Independent voltage source:
An ideal independent voltage source is one
which maintains a constant (specified)
voltage across the terminals irrespective of
the current it supplies or receives.
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In reality even the best possible
source will have some voltage
drop with the increasing current
due to its internal resistance; for
an
ideal
source
the
v-i
characteristics will be as shown in
Fig 1.2.
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Ideal
V
Real

i
Fig 1.2
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We can see that an ideal voltage
source with a perfect short circuit
at
the
terminals
impossibility
and
is
an
is
a
contradiction of terms (Fig. 1.3).
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a
+
Shorted
_
b
Fig 1.3
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An ideal current source is an
element that will maintain a
specific rate of flow of charge
regardless of the voltage that
appears across its terminals.
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The v-i characteristics is as
shown in Fig. 1.4.
a
i(t)=I

i
b
 
Fig.1.4
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A current source can never be an
open circuit – it must have a
path for the current to return.
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Thus a real voltage source
will be represented by a source
voltage V along with an internal
resistance Ri ( 0, for network
computation in many situations)
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and a real current source by a
source current along with a
shunted internal resistance (of
appreciable value)
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Dependent
Sources
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If the voltage of a voltage source
and the current through a current
source depend on some other variable
(say a voltage or current) in some part
of the network, then such sources are
dependent sources.
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There are four types of dependent sources (fig 1.5)
as shown.
+
K(t)=ij(t)
+
-
Current controlled Voltage
Source (CCVS)
iK(t)=A ij(t)
Current Controlled Current
Source (CCCS)
Fig. 1.5
-
K(t)=j(t)
Voltage Controlled Voltage
Source (VCVS)
ij=Current through jth
element in the network
iK(t)=j(t)
Vj=Voltage across an
element j of the network
Voltage Controlled Current Source(VCCS)
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(i) Current controlled voltage
source (CCVS)
(ii) Voltage controlled voltage
source (VCVS)
(iii) Current controlled current
source (CCCS) and
(iv) Voltage controlled current
source (VCCS)
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Ex 1.1:
If Vc = -10v and I1= 3A Calculate
I2 through R2 and voltage of the VCVS
I1
R1
VS
R2
+
+
Vc
-
-
0.1Vc
50I1
I2
Solution
50 I1= 50  3A = 150A= I2
/VCVS = 0.1Vc = -1V
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Series
and
parallel
connections of sources
i)
Series connections of voltage
sources
+
-
1(t)
n(t)
+
-
2(t)
vt  
+
-
3(t)
+
-

+
-
(t)
n
 v t 
i 1
i
Fig1.6
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Parallel
connections
of
ideal
voltage sources, is not defined,
except when they have identical
voltages.
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ii) Parallel connection of current
sources
i1(t)
i2(t)
i3(t)
in(t)
i(t)
n
i(t )   ik (t )
k 1
Fig. 1.7
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iii) Replacing parallel / series
connections of a set of ideal
voltage/current sources.
+
-
(t)

+
-
1(t)
+
+
- 2(t)
-
+
3(t)
- n(t)
1(t) = 2(t) = --- = n(t) = (t)
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
i(t)
i1(t)
i2(t)
i3(t)
Fig. 1.8
i1(t) = i2(t) = i3(t) = i4(t) = i(t)
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iv) Voltage and current sources
in series and parallel
+
-
+
-
(t)
i(t)

+
-
(t)
(t)
i(t)

i(t)
Fig. 1.9a
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Ex 1.2 : Calculate x, iy, iz and
the power supplied by the two
sources in Fig. 1.10.
x
iz
2V
3
+
-
iy
4
x= -2  3V = -6V
iy= 2/4 A = 0.5A
iz = -(2-0.5) A = -1.5A
2A
Fig. 1.10
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Power supplied by voltage source
= 2  -1.5 W = -3 W
Voltage across the current source
= (2 + 6) V = 8 V
Power supplied by current source
= 8  2 W = 16 W