Basic Electrical Engineering - · PDF fileAs per new revised syllabus of SPPU w.e.f....

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

Published By –

Gigatech Publishing House

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Office No. 105, First Floor, Shan Bramha Complex, Pune – 411 002 .

Phone No. 952 952 0952

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All rights reserved. No part of this publication can be stored in any retrieval system or

reproduced in and form or by any means without prior permission of the Publisher.

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author and publisher make no warranty with regard to the program and documentation

contained in the book .

ISBN NO. : 978-81-934140-64

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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

F. E. (Basic Electrical Engineering) 2 Syllabus


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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

F. E. (Basic Electrical Engineering) 2 Contents


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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

F. E. (Basic Electrical Engineering) 1.2 Elementary Concepts


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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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