Basic Electrical Engineering
Semester I & II First Year Engineering Common to All Branches As per the new revised syllabus of SSPU. w.e.f. academic year 2012-2013
Dr. B. E. Kushare
B.E. (Electrical Engg.)
M.E. (Control System), Ph.D
Hod, and Prof. Electrical Engg. Deptt.
K. K. Wagh I.E.E. & R.
Nashik
Prof. Ashok M. Jain
M.E. (Control System)
Prof. Electrical Engg. Deptt.
K. K. Wagh I.E.E. & R.
Nashik
Ms. Aastha A. Jain
Assistant professor
M.E. (Power System)
JESITM & R Nashik
Gigatech Publishing House Igniting Minds
Basic Electrical Engineering
First Year Engineering Common to All Branches
As per new revised syllabus of SPPU w.e.f. academic year 2012-2013
Dr. B. E. Kushare, Prof. Ashok M. Jain, Ms. Aastha A. Jain
First Edition : 2017
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Preface
We are delighted to present this book to the students of First Year (all
branches) from all the engineering colleges affiliated to the Savitribai Phule Pune
University.
Electrical is a mandatory subject for first year engineering students, where
almost all the important engineering elements of the subject are covered. This book is
written according to the revised (2012) curriculum of 'Basic Electrical Engineering '.
The aim of writing this book has been to present the material in a concise and simple
way so that even weak students can grasp the fundamentals. Each Unit of the book
starts with simple introduction and then related topics are covered with required
description along with the help of figures. A large number MCQ's and solved
problems, properly graded have been added in all units to enable the students to
attempt different types of questions in the university examination without any difficulty.
This book has been written after understanding the exact requirement of F.E.
(all branches) students thoroughly. We are sure that it will satisfy all the needs of F.E.
students from the Savitribai Phule Pune University.
We express our sincere thank to Hon. Prof. M. N. Navale, Founder-President
STES, Hon. Dr. (Mrs.) Sunanda M. Navale, Founder- Secretary STES, Hon. Mr Rohit
Navale, Vice president (HR), STES and Hon. Mrs. Rachana Navale – Ashtekar, Vice
President (Admin), STES as they are constant source of inspiration to us right from
the first day of our teaching carrier. We would also like to thanks Principal SCOE,
SKNCOE, NBNSOE, SAE, SITS, RMDSOE, SIT, SKNSITS, K.K.W.I.E.E.& R Nasik &
Chairman Mr. Balasaheb D. Wagh , K.K. Wagh Education Society, Nashik for their co-
operation and support. We would also thank our department colleagues for their
suggestions and timely help.
Any suggestions for the improvement of this book will be sincerely
acknowledged and incorporated in the next edition.
We are thankful to Mr. Harshal J Potadar and Rohit K Dongare from Gigatech
Publishing House (GPH) for their continuous support and patience in preparing this
book.
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SYLLABUS
Unit - I : Elementary Concepts (06 Hrs.)
Prerequisite : Concepts of emf, potential difference, current and resistance. Ohm's law,
effect of temperature on resistance, resistance temperature coefficient, insulation
resistance. S.I. units of work, power and energy. Conversion of energy from one form to
another in electrical, mechanical and thermal systems.
Unit - II : Electromagnetism (06 Hrs.)
Magnetic effect of an electric current, cross and dot conventions, right hand thumb rule
and cork screw rule, nature of magnetic field of long straight conductor, solenoid and
toroid. Concept of m.m.f., flux, flux density, reluctance, permeability and field strength,
their units and relationship. Simple series and parallel magnetic circuits, comparison of
electrical and magnetic circuit, force on current carrying conductors placed in magnetic
field, Fleming's left hand rule.
Faraday's laws of electromagnetic induction, Fleming's right hand rule, statically and
dynamically induced e.m.f., self and mutual inductance, coefficient of coupling, energy
stored in magnetic field.
Unit – lll : Single phase Transformers and Electrostatics (06 Hrs.)
A) Single phase transformers : Construction, principle of working e.m.f. equation,
voltage and current ratios, losses, definition of regulation and efficiency,
determination of these by direct loading method. Descriptive treatment of
autotransformers.
B) Electrostatics : Electrostatic field, electric flux density, electric field strength,
absolute permittivity, relative permittivity and capacitance. Capacitor, composite
dielectric capacitors, capacitors in series and parallel, energy stored in capacitors,
charging and discharging of capacitors (no derivation) and time constant.
Unit – IV : AC fundamentals (06 Hrs.)
Sinusoidal voltages and currents, their mathematical and graphical representation,
concept of cycle, period, frequency, instantaneous, peak (maximum), average and r.m.s.
values, peak factor and form factor. Phase difference, lagging, leading and in phase
quantities and phasor representation. Rectangular and polar representation of phasors.
Study of A.C. circuits consisting of pure resistance, pure inductance, pure capacitance
and corresponding voltage-current phasor diagrams, voltage-current and power
waveforms.
Unit - V : Single Phase A.C. Circuits and Polyphase A.C. Circuits (06 Hrs.)
A) Single phase A.C. Circuits : Study of series and parallel R-L, R-C, R-L-C circuits,
concept of impedance, admittance in case of above combinations, wave form and
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relevant voltage current phasor diagrams, concept of active, reactive, apparent,
complex power and power factor, resonance in series RLC circuit.
B) Polyphase A.C. Circuits : Concept of three-phase supply and phase sequence,
balanced and unbalanced load, voltage, currents and power relations in three phase
balanced star-connected loads and delta-connected loads along with phasor
diagrams.
Unit - VI : D.C. Circuits (06 Hrs.)
Classification of electrical networks. Kirchhoff's laws and their applications for network
solutions using loop analysis. Simplifications of networks using series and parallel
combinations and star-delta conversions. Energy sources - iedal and practical voltage and
current sources. Superposition theorem, Thevenin's theorem.
Recommended by SPPU Text Books and Reference Books
Text Books :
1. Principles of Electrical Engineering by Del. Toro, PHI Learning Pvt. Ltd.
2. Theory and Problems of Basic Electrical Engineering – I. J. Nagrath and Kothari, PHI
Learning Pvt. Ltd.
3. Basic Electrical Engineering, V.K.Mchta, S. Chand and Company Ltd., New Delhi.
Reference Books :
1. Electrical Technology – H. Cotton, C.B.S. Publications.
2. A Textbook of Electrical Technology : Volume – I – B. L. Theraja, S. Chand and
Comp[any Ltd, New Delhi.
3. Basic Electrical & Electronics Engg. By S. K. Bhattacharya, Pearson.
4. Basic Electrical Engineering. By D. C. Kulshreshtha, Tata Mc Graw Hill.
5. Electrical Technology – Edward Hughes, Pearson.
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CONTENTS
1. Elementary Concepts 1.1 – 1.29
1.1 The Atomic Structure
1.1.1 Electron Energy Levels and Shells
1.1.2 Valance Electrons
1.1.3 Free Electrons
1.1.4 Electricity in Motion
1.1.5 Current
1.1.5.1 Direct current
1.1.5.2 Alternating current
1.2 Potential
1.3 emf
1.4 Resistance
1.4.1 Definition of Specific Resistance or Resistivity (p)
1.4.2 Conductivity
1.4.3 Water System Analogy
1.5 Conductors, Insulators And Semi-Conductors
1.6 Ohm's law
1.7 Effect of Temperature on Resistance
1.8 Temperature Coefficient of Resistance
1.8.1 Value of temperature co-efficient at different temperature
1.9 Insulation Resistance (Rin)
1.10 Work power and energy
1.11 Joules law of electric heating
1.12 Thermal Efficiency
2. Electromagnetism 2.1 – 2.58
2.1 Magnetism and its effect
2.1.1 Laws of Magnetic Force
2.1.2 Magnetic Field
2.2 Magnetic field due to straight conductor
2.3 Cross and dot convention of current
2.4 Force on a current carrying conductor in a magnetic field
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2.5 Permeability
2.5.1 Definition of relative permeability
2.6 Solenoid
2.6.1 Magnetic field due to long solenoid
2.7 Force between two parallel current carrying conductor
2.8 Magnetic circuit
2.9 Comparison between electric and magnetic circuit
2.10 Types of Magnetic Circuit
2.11 Magnetic leakage and fringing
2.11.1 B-H Curve and Hysteresis
2.11.2 Core Losses
2.12 Faraday's law of electromagnetic induction
2.12.1 Direction of induced emf and current
2.12.2 Nature of inducted EMF
2.13 Statically induce emf
2.13.1 Self Induced emf
2.13.2 Self Inductance
2.14 Mutual Induced Emf
2.14.1 Mutual Inductance
2.15 Inductances in series
2.16 Energy stored in magnetic field
2.17 Step Response of R – L Series Circuit
2.17.1 Rise of Current in R – L Circuit
2.17.2 Decay of Current in R – L Circuit
3. Single phase Transformers and Electrostatics 3.1 – 3.44
3.1 Construction of Transformer
3.2 Principle of Transformer Action
3.3 E.M.F. Equation
3.4 Phasor Diagram of Ideal Transformer
3.5 Transformer Losses
3.6 Efficiency and Voltage Regulation
3.6.1 Determination of the Efficiency and Regulation by Direct Loading Method
3.7 Auto Transformer
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3.8 Introduction
3.9 Coulomb’s Law of Electrostatic
3.9.1 Coulombs First Law
3.9.2 Coulombs Second Law
3.10 Absolute and Relative Permittivity
3.11 Electric Field
3.12 Properties of Electric Lines of force
3.13 Electric Field Strength (E)
3.14 Electric Flux
3.15 Electric Flux Density
3.16 Relation between D and E
3.17 Electric Potential
3.18 Volt
3.18.1 Electrical Potential Difference
3.18.2 Potential Gradient
3.19 Introduction to Capacitor
3.20 Dielectric Materials used in Capacitor
3.21 Factors Affecting Capacitance
3.22 Expression for Parallel Plate Capacitor
3.22.1 Expression for parallel Plate Capacitor when Uniform Dielectric Medium
3.22.2 Medium Partly Air
3.22.3 Composite Mediums
3.23 Capacitors Connected in Series
3.23.1 Capacitors are in Parallel
3.23.2 Series Parallel Capacitor Combination
3.24 Energy Stored in a Capacitor
3.25 Charging of Capacitor Through a Resistor
3.25.1 Time Constant
3.25.2 Discharging of capacitor through Resistance
4. AC fundamentals 4.1 – 4.15
4.1 Alternating quantity
4.2 Generation of the alternating quantity
4.3 Root mean square (RMS) or Effective value
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4.4 Derivation of RMS value of full wave sinusoidal current
4.5 Average Value
4.6 Methods of phasor representation
5. Single Phase A.C. Circuits and Polyphase A.C. Circuits 5.1 – 5.59
5.1 A.C. Through Resistance
5.2 A.C. Through Pure Inductance
5.3 A.C. Through Pure Capacitance Only
5.4 A.C. Through Resistance and Inductance or Series R.L. Circuit
5.6 A.C. through Series R-L-C circuit
5.7 Parallel Connected A.C. Circuit
5.8 Poly-Phase A.C.
5.8.1 Introduction
5.9 How Voltage Generate in Three Phase ?
5.10 Advantage of Polyphase system over single phase system
5.11 Phase Sequence
5.12 Star Connection
5.13 Delta Connection
5.14 Balance system
5.15 Line and phase quantities in star connected circuit
5.16 Line and phase Quantities in Delta Connected System
6. D.C. Circuits 6.1 – 6.61
6.1 Energy Sources
6.2 Arrangement of Resistances
6.3 Necessity of star – Delta Transformation
6.4 Kirchhoff's Voltage Law
6.5 Superposition Theorem and Explanation
6.5.1 Procedure of Application of Superposition Theorem
6.6 Thevenin’s and Norton’s Theorems
6.7 Thevenin’s Theorem
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SOLVED QUESTION PAPER DEC. 2015 Q.1-Q.10
SOLVED QUESTION PAPER DEC. 2016 Q.1-Q.11
SOLVED QUESTION PAPER MAY 2016 Q.1-Q.11
SOLVED QUESTION PAPER MAY 2017 Q.1-Q.10
MCQ’S 1-92
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Syllabus
Prerequisite : Concepts of emf, potential difference, current and resistance. Ohm's law, effect
of temperature on resistance, resistance temperature coefficient, insulation resistance. S.I.
units of work, power and energy. Conversion of energy from one form to another in electrical,
mechanical and thermal systems.
1.1. The Atomic Structure :
All matters are composed of atoms. Matter composed of single type of element is called
an element. When different kinds of atoms are combined chemically they form compounds.
The atom consists of mainly two parts 1) Nucleus: The centre of the atom called as nucleus,
contains protons having positive charges and neutrons which are electrically neutral. Proton
has 1837 times as much mass as electrons. 2) The electrons which rotates in orbit around
nucleus of the atom in the same manner as the
earth rotates around the sun. Electrons have
negative charges and no. of electrons are equal
to the number of protons in an atom. Therefore,
total negative charges. Hence atom is electrically
neutral. The electron spins around the nucleus in
an elliptical path. As there is a force of attraction
between oppositely charged protons & electrons,
electron in motion remains associated with
nucleus and thus the electrons in motion have
kinetic energy.
Unit
1
Elementary Concepts
Fig. : 1.1
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1.1.1 Electron Energy Levels and Shells :
Electrons associated with nucleus possess two kinds of energy.
1) Each electron is constantly in motion about the nucleus; hence it has energy of motion or
kinetic energy.
2) Because of force of attraction between negatively charged electrons and positively
charged protons in nucleus, hence electrons posses potential energy. If an electron is
nearer to nucleus the greater kinetic energy it possesses. If it is far away from the
nucleus the greater potential energy it possesses. Kinetic energy develops force that
pulls the electrons away from nucleus and potential energy arises from charge attraction
that pulls towards the nucleus. At certain energy level equilibrium is established and the
electron goes into the orbit. The atoms of different elements have different number of
electrons and protons. As the number of electrons and protons increases their
arrangement around the nucleus follow a known pattern with each energy level able to
hold only definite maximum electrons. These energy level groups are called as shells,
labelled as K, L, M, N, O, P, Q reading from nucleus outwards, each shell (orbit) has a
fixed capacity to accommodate electrons. If the number of electrons exceeds the
capacity of a particular shell the next shell is occupied. The following relation is valid for
determining the number of electrons in first four shells of an atom, but is not generally
applicable for atoms containing additional shells N = 2n2 where n is the shell number.
Table 1.1 gives maximum number of electrons in a shell.
Shell Max. Electrons (N)
K 2(1)2 = 2
L 2(2)2 = 8
M 2(3)2 = 18
N 2(4)2 = 32
O 18
P 18
Q 2
Fig. : 1.2 Diagram of Copper Atom
The outermost shell of an atom is known as valance shell, in case of copper atom, the
electrons in valance shell is one, though it has a capacity to accommodate 32 electrons.
1.1.2 Valance Electrons :
The electrons in the outermost shell of an atom are called as valance electrons
which are involved in chemical reaction and electric current. The force of attraction between
nucleus and electrons decreases as the electrons situated away from nucleus. Thus valance
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electrons are held to the nucleus with less force of attraction than the inner shell electrons.
Hence valance electrons can be easily removed from the parent atom than the electrons in the
inner shells. In general the farther the electrons from the nucleus, the more energy it
possesses. Hence valance electrons posses more energy than the inner shell electrons.
1.1.3 Free Electrons :
As we known that valance electrons are associated with parent atom with less force of
attraction, and it is at maximum energy level than inner shell electrons. Once valance electrons
gain additional external energy sufficient to overcome the force of attraction towards nucleus, it
gets temporarily separated from parent atom. The valance electrons separated from parent
atoms are free to wander in a space around the atom, hence are called as free electrons.
Only the valance electrons are capable of becoming free electrons. One way to provide
additional energy to free an electron is to heat the atom. The other way is the atom is
subjected to an electronic field. In an copper atom the external energy is in the form of heat at
room temperature which is sufficient to detach the valance electrons from copper atom. Hence
in case of copper material at room temperature large number of free electrons is available
which are drifting in random way.
1.1.4 Electricity in Motion :
As from the previous section it is clear that the valance electrons are held with less force
of attraction. Whenever the valance electrons will gain additional energy sufficient to overcome
the force of attraction towards nucleus, the valance electrons will get separated from parent
atom and become free electrons. In case of copper atom, the external energy required to
detach the valance electrons from parent atom is available at room temperature. Hence in
case of copper at room temperature large number of free electrons are available, moving in a
copper material in a random way. Hence in case of isolated copper conductor though large
number of free electrons is available at room temperature, but because of their random motion
there is no resultant motion of electrons in a specified direction as shown in fig. 1.3. Hence
there is no net transfer of charge. Hence to direct the free electrons moving in a random
direction some external force is needed. Let us consider a simple arrangement as shown in fig.
1.4. As long as the switch is open there is no resultant motion of electrons in a specified
direction. As soon as the switch is closed, the positive terminal (which has deficiency of
electrons) of a cell attracts free electrons of copper wire, because of dissimilar charges attract
each other. The –ve terminal of the cell has excess of electrons. Hence free electrons in
copper wire connected to –ve terminal will experience force of repulsion tending to move the
free electrons from –ve terminal of battery through copper wire towards the positive terminal of
batter. At the same time equal number of electrons travel within the cell from +ve to –ve
terminal of the cell. Thus from the above simple experiment, it is clear that when we connect
the cell and complete the circuit the electrons are set in motion. As we know that the electrons
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have negative charges, hence motion of electrons within copper conductor are nothing but a
transfer of charge (i.e. negative charge) from one point to another point in a circuit. This
continuous stream of electrons in a specified direction constitutes electric current. The
direction of flow of electrons is from –ve to +ve terminal, but the conventional direction
of current is always considered as being from +ve to –ve terminal. (Outside the battery as
shown in fig. 1.4)
Fig. 1.3 : at room temp. before switching on
free electrons moves in a random fashion.
Fig. : 1.4
1.1.5 Current :
It is defined as the rate of flow of charged particles in a specified direction. The
charged particles may be an electron, a positive ion or a negative ion. In a solid the charged
particle is electron.
Electric current exists in a material when there is a net transfer of charge through the
material from one region to another region and is measured in terms of the rate at which the
charge is transferred past a point per unit time.
i = dq
dt
Basic Electrical Engineering Semester IAnd II (Common for all branches)
Publisher : Gigatech PublishingHouse
ISBN : 9788193414064Author : B E Kushare,Ashok M Jain And Aastha AJain
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