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ELECTRICALAND

ELECTRONICSENGINEERING

SANJEEV GUPTA B.E., M.B.A.

(Strictly as per latest RGPV Syllabus)

Price : Rs. 195.00

First Edition : 2011

© Author

Published by:Ish Kapurfor Dhanpat Rai Publications (P) Ltd.,Typeset by Phoenix Computer Centre, andPrinted at Taj Press, New Delhi.

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PREFACE TO THE FIRST EDITION

The book “Electrical and Electronics Engineering” has been written for the first yearEngineering Students according to the latest RGPV Syllabus. The aim of writing this book is toprovide the students with a clear and logical presentation of the subject, basic concepts,principles and their link with physical phenomena. The book is written in a very simple wayand every effort has been made to make the treatments simple, comprehensive and complete.The subject matter has been developed in a step by step way for easy understanding.Throughout the book, the stress has been given on fundamental concepts through illustrativeexamples and figures. To clarify the concepts and making the topics interesting, a number ofsolved examples are incorporated at appropriate places. Practical exercises, problems and anumber of objective type questions with their answers are given at the end of each chapter.

The book is divided into five units. The first unit is devoted to the basic ideas of ElectricalCircuit Analysis including the different theorems used for Circuit Analysis. The second unitemphasises on the Basic Concepts of Transformers. The constructional details, workingprinciples and explanations of D.C. Machine, Induction Machine and Synchronous Machineare discussed in the third unit under the head of Rotating Electric Machines. Unit fourthexplains the different number systems, theorems and different gates under Digital Electronics.The last unit fifth throws light on the Electronic Components and Circuits which are the basisof Electronic Engineering.

Inspite of my best efforts, it is possible that some unintentional errors might have crept in. Ishall acknowledge with gratitude any such errors brought to my notice. Suggestions fromstudents and Professors for improvement of the book would be thankfully acknowleged.

I hope that the book will be useful for the readers.

DELHI Sanjeev Gupta

SYLLABUS(RGPV Syllabus)

ELECTRICAL AND ELECTRONICS ENGINEERINGB.E. - 104

UNIT - I

Electrical Circuit Analysis: Voltage and current sources, dependent and independent sources,source conversion, DC circuits analysis using mesh and nodal method, Thevenin’s andsuperposition theorem, star-delta transformation. 1-phase AC circuits under sinusoidal steadystate, active, reactive and apparent power, physical meaning of reactive power, power factor,3-phase balanced and unbalanced supply, star and delta connections.

UNIT - II

Transformers: Review of laws of electromagnetism, mmf, flux, and their relation, analysis ofmagnetic circuits. Single-phase transformer, basic concepts and construction features, voltage,current and impedance transformation, equivalent circuits, phasor diagram, voltageregulation, losses and efficiency, OC and SC test.

UNIT - III

Rotating Electric Machines: Constructional details of DC machine, induction machine andsynchronous machine, working principle of 3-Phase induction motor, EMF equation of 3-Phaseinduction motor, concept of slip in 3-Phase induction motor, explanation of Torque-slipcharacteristics of 3-Phase induction motor, classification of self excited DC motor andgenerator.

UNIT - IV

Digital Electronics: Number systems used in digital electronics, decimal, binary, octal,hexadecimal, their complements, operation and conversion, floating point and signednumbers, Demorgan’s theorem, AND, OR, NOT, NOR, NAND, EX-NOR, EX-OR gates and theirrepresentation, truth table, half and full adder circuits, R-S flip flop, J-K flip flop.

UNIT - V

Electronic Components and Circuits: Introduction to Semiconductors, Diodes, V-I charac-teristics, Bipolar junction transistors (BJT) and their working, introduction to CC, CB and CEtransistor configurations, different configurations and modes of operation of BJT,DC biasing of BJT.

CONTENTS

Preface to the First Edition (iii)

UNIT - IELECTRICAL CIRCUIT ANALYSIS ____________________________________________1.1 - 1.66

1.1 Voltage and Current Sources 1.21.2 Independent and Dependent Sources 1.31.3 Source Conversion 1.41.4 Kirchoff’s Laws 1.61.5 D.C. Circuit Analysis using Mesh Method 1.7

Solved Examples 1.91.6 D.C. Circuit Analysis using Nodal Method 1.17

Solved Examples 1.221.7 Theorem 1.231.8 Superposition Theorem 1.23

Solved Examples 1.241.9 Thevenin’s Theorem 1.27

Solved Examples 1.291.10 Star-delta Transformation 1.35

Solved Examples 1.371.11 Terms Related to Sinusoidal Waveform 1.431.12 Active Power and its Value in Pure Resistive Circuit 1.441.13 Active and Reactive Power in Inductive Circuit 1.451.14 Active and Reactive Powers in Pure Capacitive Circuit 1.471.15 Power in General Series circuit 1.471.16 Physical Meaning of Reactive Power 1.491.17 Physical meaning of Power Factor 1.49

Solved Examples 1.501.18 Introduction to Three Phase Systems 1.511.19 Three-Phase Balanced and Unbalanced Supply 1.531.20 Star and Delta Connections 1.531.21 Three-Phase Circuit Voltages/Currents [Double Subscript Notation] 1.541.22 Star Connection (Voltage and Current Relations) 1.541.23 Delta Connection (Current Relationship) 1.571.24 Power Equations in Three-Phase Circuits 1.58

Solved Examples 1.591.25 Comparison Between Star and Delta Connections 1.60

Exercises and Problems 1.62

(vi) Contents

UNIT - IITRANSFORMERS __________________________________________________ 2.1 - 2.45

2.1 Electromagnetic Induction and Electromagnetism 2.12.2 Review of Laws of Electromagnetism 2.22.3 Few Definitions 2.32.4 Magentic Circuit 2.42.5 Comparison Between Magnetic and Electric Circuits 2.52.6 Magnetic Circuit with Air Gap 2.7

Solved Examples 2.82.7 Introduction to Transformer 2.112.8 Basic Principle and Operation 2.112.9 Construction of Transformer 2.12

2.10 Ideal Transformer 2.142.11 E.M.F. Equation of a Transformer 2.15

Solved Examples 2.162.12 Transformer on No-Load (Secondary Operation) 2.172.13 Transformer on Load 2.182.14 Phasor Diagram of a Loaded Transformer 2.20

Solved Examples 2.212.15 Equivalent Values Referred to Primary 2.222.16 Equivalent Circuit (Using Voltage, Current and Impedance Transformation) 2.23

Solved Examples 2.252.17 Losses in a Transformer 2.28

Solved Examples 2.292.18 Efficiency 2.30

2.18-1 Condition for Maximum Efficiency of a Transformer 2.31Solved Examples 2.31

2.19 Voltage Regulation 2.33Solved Examples 2.342.19-1 Condition for Maximum Regulation 2.36

2.20 Open Circuit or no Load Test (O.C. Test) 2.362.21 Short Circuit or Impedance Test (S.C. Test) 2.38

Solved Examples 2.38Exercises and Problems 2.43

UNIT - IIIROTATING ELECTRICAL MACHINES___________________________________ 3.1 - 3.28

3.1 Introduction to Electro-Mechanical Energy Conversion 3.13.2 Construction of A DC Machine 3.2

3.2-1 Types of Armature winding 3.43.3 Introduction to Synchronous Machine 3.53.4 Constructional Features of A Synchronous Machine 3.6

3.4-1 Synchronous Generator / Alternator 3.83.4-2 Synchronous Motor 3.8

3.5 Introduction to Induction Machine 3.93.6 Construction of 3-Phase Induction Motors 3.93.7 Working Principle of 3-Phase Induction Motor 3.113.8 Concept of Slip 3.12

Contents (vii)

3.9 Rotor Current (or EMF) Frequency 3.13Solved Examples 3.13

3.10 EMF Induced in Rotor 3.153.11 Rotor Reactance, Current and Power Factor 3.16

Solved Examples 3.173.12 Rotor Torque τ 3.173.13 Torque Slip Characteristics 3.18

Solved Examples 3.203.14 Classification of Self-Excited D.C. Motors 3.203.15 Classification of Self Excited D.C. Generators 3.22

Exercises and Problems 3.23

UNIT - IVDIGITAL ELECTRONICS _____________________________________________________4.1 - 4.59

4.1 Introduction 4.14.2 The Decimal Number System 4.24.3 Binary Number System 4.34.4 Decimal to Binary Conversion 4.54.5 Binary to Decimal Conversion 4.64.6 The Octal Number System 4.74.7 Conversion of Octal Number into Decimal Number 4.84.8 Conversion of Decimal Number into Octal Number 4.84.9 Conversion of Octal Number into Binary Number 4.9

4.10 Conversion of Binary Number into Octal Number 4.94.11 Hexadecimal Number System 4.104.12 Conversion of Hexadecimal Number into Decimal Number 4.114.13 Conversion of Decimal Number into Hexadecimal Number 4.114.14 Conversion of Binary Number into Hexadecimal Number 4.124.15 Conversion of Hexadecimal into Binary Number 4.124.16 Binary Addition 4.134.17 Binary Substraction 4.144.18 Floating Point Numbers 4.154.19 Signed and Unsigned Number 1’s and 2’s Complements 4.164.20 1’s Complemental Subtraction 4.174.21 2’s Complemental Subtraction 4.184.22 9’s and 10’s Complements in Decimal Number System 4.194.23 Binary Multiplication and Division 4.204.24 Boolean Algebra 4.214.25 Laws of Boolean Algebra 4.224.26 Basic Logic Gates 4.274.27 OR Addition 4.284.28 AND Multiplication 4.304.29 The NOT Circuit 4.324.30 De-Morgan’s Theorem 4.364.31 NAND Gate 4.394.32 NAND Gate is a Universal Gate 4.404.33 NOT Gate 4.414.34 NOR Gate is a Universal Gate 4.42

(viii) Contents

4.35 Exclusive-or Gate (XOR Gate) 4.434.36 Exclusive-nor Gate (Ex-NOR Gate) 4.444.37 Logic Gates at a Glance 4.464.38 Half-Adder 4.464.39 Full Adder 4.474.40 Half Subtractor 4.494.41 Full Subtractor 4.504.42 Sequential Logic Circuits 4.504.43 Rs Flip-flop 4.51

Exercises and Problems 4.54

UNIT - VELECTRONIC COMPONENTS AND CIRCUITS __________________________________5.1 - 5.68

5.0 Introduction to Semiconductors 5.15.1 Chemical Bonds in Semiconductors like Germanium and Silicon 5.25.2 Effect of Temperature on Semiconductors 5.35.3 Mechanism of Conduction in Electrons and Holes 5.45.4 Pure or Intrinsic Semi-conductors and Impure or Extrinsic Semi-conductors 5.55.5 N-type Extrinsic Semiconductor 5.65.6 P-type Extrinsic Semiconductor 5.85.7 Majority and Minority Charge Carriers 5.95.8 Mobile Charge Carriers and Immobile Impure 5.95.9 P-N Junction Diode 5.10

5.10 Working of Diode 5.125.11 Volt-Ampere Characteristics of P-N Junction 5.145.12 Important Terms 5.155.13 The Bipolar Junction Transistor (BJT) 5.185.14 Transistor Biasing 5.205.15 Different Modes of Operation of a Transistor 5.215.16 Operation of PNP Transistor 5.225.17 Operation of NPN Transistor 5.235.18 Transistor Circuit Configurations 5.235.19 Common-Base (CB) Configuration 5.245.20 Common-Emitter (CE) Configuration 5.275.21 Common-Collector (CC) Configuration 5.295.22 Characteristics of Common Base Circuit 5.315.23 Characteristics of Common Emitter Circuit 5.335.24 D.C. Equivalent Circuit 5.36

Solved Examples 5.375.25 Transistor Biasing 5.405.26 Different Methods for Transistor Biasing 5.425.27 Base Resistor Method 5.425.28 Collector to Base Bias 5.455.29 Base Bias with Collector and Emitter Feedbacks 5.485.30 Self Bias or Emitter Bias (Voltage Divider Bias) 5.515.31 Transistor Biasing 5.40

Solved Examples 5.54Exercises and Problems 5.62

UNIT-1

ELECTRICALCIRCUIT ANALYSIS

INTRODUCTIONElectricity is modern society’s most convenient, useful and popular form of energy. It hasnumerous applications such as lighting, heating, cooling, transportation, entertainment and soon. Modern human being is totally dependent on electricity and we cannot even think of a lifewithout it. In short, electricity has now become the universal medium for transmission andutilization of energy.

The subject of Electrical Engineering forms a basic course for all Engineering graduates asit provides a foundation for all branches of engineering. In one way or the other electricity andin turn laws of electrical engineering provide a base for all branches of engineering. This chapteris devoted to Electrical Circuit Analysis. The following electric circuit terminology are used:

(i) Circuit. It is a conducting path through which an electric current either actually flowsor is intended to flow.

(ii) Parameters. The various elements such as resistance, inductance, capacitance, etc of anelectric circuit are called as parameters.

(iii) In terms of circuit parameters, a circuit may be: (a) Linear circuit, (b) Non-linear circuit(c) Bilateral circuit (d) Unilateral circuit(a) Linear circuit. If the circuit parameters do not change with voltage or current, the

circuit is called as linear circuit. (b) Non-linear circuit. When the circuit parameters change with voltage or current, the

circuit is called as non-linear circuit. (c) Bilateral circuit. When the properties or characteristics of a circuit are same in either

direction, it is called bilateral circuit. Transmission lines are the example of bilateralcircuit.

(d) Unilateral circuit. When the properties or characteristics are not same in eitherdirection, the circuit is called as unilateral circuit. Diode is an example of unilateralcircuit.

(iv) Electric network. When various electrical elements (resistance, inductance, capacitanceetc) are connected in a circuit in any manner (in series or parallel), it is called as electricnetwork. The electric network may be:

(a) Passive network (b) Active network (a) Passive network. When a network does not contain any source of e.m.f in it, it is

called as passive network. (b) Active network. When a network contains at least one source of e.m.f. in it, it is called

as active network.

(v) Active element. The element which supplies energy to the circuit is called as activeelement. For example, a battery connected in the circuit is an active element.

(vi) Passive element. The element which receives energy in a circuit is called as passiveelement (such as resistor, inductor and capacitor).

(vii) Node. A point in the network where two or more circuit elements are joined is called anode.

(viii) Branch. The part of the network that lies between the two junctions is called as branch.

1⋅1 VOLTAGE AND CURRENT SOURCES

Source

A Source is a device which converts mechanical, chemical, thermal or some other form of energyinto electrical energy. Hence, we can say that source is an active network element meant forgenerating electrical energy. The different types of sources available are voltage sources andcurrent sources. A voltage source has the forcing function of e.m.f. whereas the current source hasthe forcing function of current. Example of voltage sources are batteries and alternators. Exampleof current sources are photo electric cells, collector current of transistors etc. These sources arefurther categorised as ideal source or practical source.

Voltage Source A voltage source is a two terminal device whose voltage at any instant of time is constant andis independent of the current drawn from it. Such a voltage source is called as ideal voltage sourceand have zero internal resistance. In practice, such an ideal voltage source cannot be obtained.However, smaller is the internal resistance r of a voltage source, closer it is to an ideal source.Fig. 1⋅1 shows an ideal voltage source and a practical voltage source.

Let the ideal voltage of the voltage source is 12 V (No load current). If its internal resistanceis 0.01 Ω and the load current increases to 100 A, then

voltage of ideal voltage source, V0 = 12 volt .

and voltage of practical voltage source V0′ = 12 − 1 = 11 volt.

Figure 1⋅2 shows the symbol and characteristics of an ideal voltage source and practicalsource.

Fig. 1⋅1

1.2 Electrical and Electronics Engineering

Current source An ideal current source is a two terminal circuit element which supplies the same current to anyload resistance connected across its terminals. It is important to mention here that currentsupplied by the current source is independent of the voltage of source terminals.

Figure 1⋅3 shows the symbol and characteristics of an ideal and practical current source.

1⋅2 INDEPENDENT AND DEPENDENT SOURCES

Independent Sources The ideal voltage source and ideal current source discussed in previous article come under thecategory of independent sources.

The independent source is one which does not depend on any other quantity in the circuit.It has a constant value i.e., the strength of voltage or current is not changed by any variation inthe connected circuit. Thus, the voltage or current is fixed and is not adjustable.

Dependent Sources The source whose output voltage or current is not fixed but depends on the voltage or currentin another part of the circuit is called as dependent or controlled source.

The dependent source is basically a three terminal device. The three terminals are pairedwith one common terminal. One pair is referred as input while the other pair as output. Forexample, in a transistor, the output voltage depends upon the input voltage.

The dependent sources are represented by diamond shaped box as shown in Fig. 1⋅4.

The dependent sources can be categorised as:

1. Voltage dependent voltage source Fig. 1⋅4 (a). 2. Current dependent voltage source Fig. 1⋅4 (b).

Fig. 1⋅3

Fig. 1⋅2

Electrical Circuit Analysis 1.3

3. Voltage dependent current source Fig. 1⋅4 (c). 4. Current dependent current source Fig. 1⋅4 (d).

Classification of Sources The classification of sources is shown in Fig. 1⋅5.

1⋅3 SOURCE CONVERSIONIt is most important part of the circuit analysis. To simplify the circuit, certain rules have beenframed which are given below:

(a) A voltage source having some resistance can be replaced by the current source in parallelwith the resistance as shown in Fig. 1⋅6.

Fig. 1⋅5

Fig. 1⋅6

Fig. 1⋅4

1.4 Electrical and Electronics Engineering

The direction of current source is in the direction of voltage rise.

(b) A current source in parallel with some resistance can be replaced by a voltage source inseries with the same resistance as shown in Fig. 1⋅7.

(c) Voltage sources in series are transformed, as in Fig. 1⋅8.

(d) Voltage sources in parallel must have same value as in Fig. 1⋅9.

(e) Current sources in parallel are transformed as shown in Fig. 1⋅10.

(f) Current shift property is as shown in Fig. 1⋅11.

Fig. 1⋅10

Fig. 1⋅9

Fig. 1⋅8

Fig. 1⋅7

Electrical Circuit Analysis 1.5

(i) Voltage shift property is as shown in Fig. 1⋅12.

The above mentioned rules are very helpful in circuit analysis for simplifying the circuit.

Example 1. Convert the voltage source of Fig. 1⋅13 (a) into a current source.

Solution. Given V = 20 V and Rx = 1 k Ω = 1 × 103 Ω

Now I = VRx

= 201 × 103 = 20 × 10− 3 = 20 mA

The equivalent circuit is shown in Fig. 1⋅13 (b).

1⋅4 KIRCHOFF’S LAWSOhm’s law is unable to give current in complicated circuits. Kirchoff in 1842, gave two generallaws which are extremely useful in electrical circuits. These are :

(i) The algebraic sum of the currents at any junction in a circuit is zero, i.e.,

Σ i = 0 …(1)

Fig. 1⋅13

Fig. 1⋅12

Fig. 1⋅11

1.6 Electrical and Electronics Engineering

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