Gateway to...psus (Synopsis, ultiple Choice Questions and their Explanatory Notes) For Electronics & Telecommunication Engineering (ETE), Electronics & Communication Engineering (ECE), Electrical & Electronics Engineering (EEE), Electronics & Instrumentation Engineering (EIE) Useful for Bharat Electronics Limited (BEL). Bharat Heavy Electronics Limited (BHEL). Steel Authority India Limited (SAIL). Hindustan Aeronautics Limited (HAL). Indian Oil Corporation Limited (IOCL). National Thermal Power Corporation Limited (NTPC). National Fertilizers Limited (NFL). Centre for Development of Telematics (C-DOT). Power Grid Corporation of India Limited (PGCIL). Hindustan Petroleum Corporation Limited (HPCL). Larsen & Tubro Limited (L & T). Indian Farmers Fertilizers Corporation Limited (IFFCO). Bhabha Atomic Research Centre (BARC). Indian Space Research Organization (ISRO). Defence Research Development Organization (DRDO), etc. By Ashish Dixit Phd. Persuing.Tech. (.L.S.I. Design) C-DAC, ohali (Punjab) B.Tech. (HONs E & T) Sr. Lecturer (EC Deptt.) AITY UNIERSITY Lucknow Seccond Revised Edition Upkar Prakashan, AGRA-
Authors Publishers UPKAR PRAKASHAN (An ISO 900 : 000 Company) /A, Swadeshi Bima Nagar, AGRA8 00 Phone : 05, 50966, 50 Fax : (056) 050, 0570 E-mail : care@upkar.in, Website : www.upkar.in Branch Offices : 85, Ansari Road, Daryaganj, New Delhi 0 00 Phone : 058/66 8, Chowdhury Lane, Shyam Bazar, Near etro Station, Gate No. Kolkata 70000 (W.B.) Phone : 055550 Pirmohani Chowk, Kadamkuan, Patna 800 00 Phone : 06670 B-, Blunt Square, Kanpur Taxi Stand Lane, awaiya, Lucknow 6 00 (U.P.) Phone : 0509080-8-/B, R.R. Complex (Near Sundaraiah Park, Adjacent to anasa Enclave Gate), Bagh Lingampally, Hyderabad 500 0 (A.P.) Phone : 0066750 The publishers have taken all possible precautions in publishing this book, yet if any mistake has crept in, the publishers shall not be responsible for the same. This book or any part thereof may not be reproduced in any form by Photographic, echanical, or any other method, for any use, without written permission from the Publishers. Only the courts at Agra shall have the jurisdiction for any legal dispute. ISBN : 978-8-78-9-9 Price : 850 00 (Rs. Eight Hundred Fifty Only) Code No. 657 Printed at : UPKAR PRAKASHAN (Printing Unit) Bye-pass, AGRA
Heartiest Thanks To r. Aseem Kumar Chauhan Additional President (Ritnand Balved Education Foundation) AITY UNIERSITY Uttar Pradesh & aj. Gen. K. K. Ohri AS Retd. Director General AITY UNIERSITY Lucknow Campus
Dedicated to Grandfather Late r. Ram Prasad Dixit Father r. Uidya Dhar Dixit & other Smt. ithlesh Dixit
PREFACE It is a matter of great pleasure to present this book Gateway to PSUs. Getting a job in the PSUs like BSNL & SNL and other PSUs like, DRDO, ISRO, NTPC, GAIL, BHEL, BARC, NHPC, SAIL, IOCL etc. has always been an aspiration of engineering graduates. Although a number of books are available for entrance examinations for these jobs, the present book makes a significant departure from its predecessors because of its encyclopaedic subject matter and its innovative and lucid presentation. I am sure that this book will provide complete satisfaction to the readers. Presently the market scenario is confusing and it is hard to find the optimum quality books. While preparing this manuscript, I continuously kept in mind the requirements of the aspirants regarding the latest trends of these entrance examinations as well as the most intricate concepts involved. This book is divided into twenty units. Each unit begins with a synopsis and ends with multiple choice questions and their explanatory notes. The variety and quality of problems also makes this book unique and an asset for the aforementioned examinations. Salient Features of the Book Synopsis has been given in the beginning of each topic for a quick and easy review just before the examination. ore than 500 objective solved problems. Special tricks are given to solve the objective problems in order to save the time during examination. It covers many objective problems frequently asked in various competitive examinations. For a better understanding many problems have been solved graphically. Previous years question papers fully solved. This work has come into being only because of the unparallel help and support that came from r. Ankit Singh, r. Ankit Jain, r. ayank Srivastava, r. Kranti Kumar, r. Dheeraj Shukla, r. Pawan Kumar Saini. Their contribution to this work is second to none. No words are sufficient to express my gratitude to Sri idya Dhar Dixit, Avatar Singh, rs. ithlesh Dixit, r. Radhesyam Dixit, r. Prakash Dixit, Paramjit Kaur, Uday Shanker Trivedi, Anita Trivedi, Archana and Amita, Sukhwinder Kaur, Jasvinder Kaur and elder brother Suresh Kumar Tripathi and wife Annapurna, for their cooperation, patience and support during the preparation of the manuscript. We would like to thank all our friends like Akhilesh Shukla, Satish Shukla, Ankit Kumar Singh, Dheeraj Shukla, ayank Srivastava, Pawan Saini, Sarika ishra, Abhishek Dwivedi, Anand Singh Chauhan, Rohit Singh, Rajeev Singh, Ganga Raju, Talvinder Kaur, Umesh Pandey rs. ehga Singhla and Shivendra Singh Chauhan for their encouragement during the preparation of the book. We would also like to thank all our parents like r. ohan Chandra Tripathi, r. Nageswar Nath Upadhyay (IAS General- Secretary) r. Shankari Singh Chauhan, r. Surya Kumar Tripathi, r. Ram Sevak Singh Chauhan, r. Lallan ishra, r. Bindadin Singh Chauhan, r. Santa Kumar Dixit, r. Ram Gopal Singh Chauhan, r. Suresh Kumar Tripathi, r. Dev Chaitanya Brahmachari, r. Om Prakash Yadav, Dinesh Jaiswal, Sanjay Dixit, ohd. Irsad Khan (LA Sarojininagar Lucknow). I wish to express my gratitude to r. ahendra Jain, Upkar Prakashan, Agra, for publishing this manuscript. Suggestions for the improvement of this book will be greatly acknowledged and incorporated in the next edition. Ashish Dixit
ACKNOWLEDGENT I am very much grateful to a number of colleagues who have given us enormous contributions and cooperation during the preparation of the manuscipt of this book. I would like to give my hearty thanks to the following persons for their continuous support, encouragement throughout this book, like... Prof. S. K. Jha (CEST, Lucknow), Prof. Anuj Goel (H.O.D. EC B. N. Institute, Lucknow, iss Shrushut (CEST Lucknow), r. B. K. Chauhan (N.I.E.C. Lucknow), rs. Indu Prabha Singh (H.O.D. EC S.I.T.., Unnao, r. Sameer Srivastava (S.I.T.. Barabanki), r. Rahul ishra (Dr..C. Saxena, Lucknow), Dr. anish Gupta, AITY UNIERSITY, Lucknow, r. arut Tiwari, r. Prabhaker Dubey, N. I. E. C., Lucknow. r. Gurumohan Singh & rs. Shivani Wadhwa, r. H.S. Sagar Director, SBBSIET, Jalandhar, Dr. Arun Khosla, Dr. B.R. Sood Professor, SBBSIET, Jalandhar, r. Kamaljit Singh Professor, NIT, Jalandhar, Dr. Sukhbeer Bindra Professor GNDN, Amritsar, r. Neeraj Sharma Senior Lecturer IET, Chandigarh, r. andeep Singh Engineer BEL, Ghaziabad, Dr..L. Singla Scientist F, Deputy Director CSIO, Punjab, r. anish Gupta, r. Kidwai Siddique, H.O.D. Electronics AIET, Lucknow, r. Anand Chopra, r. Bhabhaya Alankar Lecturer, N.I.T. Jalandhar, r. Ankit Kumar Senior Lecturer, AIET Lucknow, r. Sanjay Jain Indian Engineering Services, r. Abhishek Agrahari Design Engineer N.I.T. Surat, r. Bijendra Saini, (IES), rs. Lalita Sharma Senior Lecturer, I.E.T. Khandari, Agra, r. Yogendra Kumar Prajapati Senior Lecturer,.I.E.T. Bijnour, r. Puneet Chandra Srivastava, Associate Professor R.K.G.I.T. Ghaziabad, r. ivek Srivastava Senior Lecturer, N.I.E.T. Greater Noida, r. Sanjay Singh GAIL, India, iss Aplana Sharma, Dr. P.K. Pandey (H.O.D. EC PGI, Lucknow), r. Pawan Yadav, r. C.K. Dixit, r. Ravi Kant, r. Satendra Yadav HOD EC Deptt., B.B.I.E.T. Bulandsahar, r. Rafeek Ahmad, r. inod Kumar Yadav and iss Smriti Agrawal. I would like to express my special thanks to r. Ambika isra, Secretary Ambalika Institute of anagement & Technology Lucknow, Dr. S. Q. Abbas, Director, Ambalika Institute of anagement and Technology, Lucknow, Dr. Alok Kumar ishra, Additional Director Ambalika Institute of anagement and Technology, r. Sunil Kumar, Dean Academic, Ambalika Institute of anagement and Technology, Lucknow, r. U. P. Singh, Dr. ansi ishra, r. Sandeep Dwivedi, r. Ravi Kumar Tiwari, r. Sonu Kumar Rai, iss Anuradha Yadav, iss Sabika Ahmad, iss onika & Prof. Karmakar all from Ambalika Institute of anagement and Technology, Lucknow. I would also like to express my special thanks aj Gen. K.K. Ohri, Prof. S.T.H. Abidi, Prof. N.R. Yadav, Dr. O.P. Singh, r. Arun Pathak, Dr. Neetu Agrawal, rs. Gitika Srivastawa, iss Sarika ishra, r. Zia Abbas, r. Anupam, r. Sachin Kumar, r. Yashu Swami, Dr. Amit kumar ishra, r. Anirudh Banergi, r. Sienu Rizavi, r. Loknath ishra, r. Rajinder Tiwari, Dr. Nidhi athur, iss Shilpi Bisth and r. Sudhir Pandey AITY UNIERSITY Lucknow Campus. Ashish Dixit
CONTENTS. Network & Systems 6 Objective Problems on Switching 8 Answers with Explanatory Notes. 0 Objective Problems : Level... Answers with Explanatory Notes. 6 Objective Problems : Level... 05 Answers with Explanatory Notes. 6. Electronics Devices 96 Objective Problems 8 Answers with Explanatory Notes. 5 iscellaneous Problems... 7 Answers with Explanatory Notes. 88. Analog Circuits 88 Objective Problems 9 Answers with Explanatory Notes. 6. Digital Circuits 56 Objective Problems : Level... 8 Answers... Objective Problems : Level (i) Problems of Boolean Theorems and Logic Gates Answers with Explanatory Notes. 7 (ii) Problems on Combinational Logic Circuits.. Answers with Explanatory Notes. (iii) Problems on Sequential Circuits : Flip-Flop 5 Answers with Explanatory Notes. 8 (iv) Problems on Counter..... 9 Answers with Explanatory Notes. 5 (v) Problems on Register...... 5 Answers..... 5 (vi) Problems on emory Organisation.. 5 Answers with Explanatory Notes. 55 5. icroprocessor 6 Objective Problems : Level... 6 Answers with Explanatory Notes..... Short Answer Type Questions.. 6 iscellaneous Problems on Digital Circuits & icroprocessor.. 7 Answers with Explanatory Notes. 7 6. Signals & Systems Objective Problems 5 Answers with Explanatory Notes. 7 7. Control Systems 76 Objective Problems Answers with Explanatory Notes. 7 8. Communications 56 Objective Problems : Level... 5 Answers with Explanatory Notes. 8
( xii ) Objective Problems : Level 9 Answers with Explanatory Notes. 5 Objective Problems : Level 6 Answers with Explanatory Notes. 7 9. Electromagnetics 60 Objective Problems : Level Answers with Explanatory Notes. 6 Objective Problems : Level 7 Answers with Explanatory Notes. 0.Power Electronics 5 Objective Problems : Level 5 Answers... 0 Objective Problems : Level Answers... 5. icrowave Engineering Objective Problems : Level 9 Answers... 6 Objective Problems : Level 7 Answers with Explanatory Notes..Optical Fibre Communication 6 Objective Problems 5 Answers with Explanatory Notes..Electrical Engineering aterials 9 Objective Problems 5 Answers with Explanatory Notes..easuring Instruments Objective Problems Answers with Explanatory Notes. 6 5.Satellite Communication Objective Problems Answers with Explanatory Notes. 6.Radar Engineering Objective Problems 6 Answers with Explanatory Notes. 9 7.Television 6 Objective Problems 6 Answers with Explanatory Notes. 6 8.Computer Engineering 6 9.Dictionary of Electronics 6 0.General Ability Test odel Question Papers 9 Practice Paper -.. Answer with Hints... Practice Paper -... Answer with Hints... Practice Paper -... 9 Answer with Hints... 57 Practice Paper -... 67 Answer with Hints... 78
Network and Systems
NETWORK AND SYSTES Kirchhoff oltage Law (KL) is a consequence of the law of conservation of energy, voltage being the energy (or work) per unit charge. Kirchhoff Current Law (KCL) is the consequence of conservation of charge. Since the algebraic summation of the charge must be zero, the time derivative of this summation must also equal to zero. Star to Delta Transformation B R B A R A O R AB = R C C R AB B A R BC R A R B R B R C R C R A R C or R AB = R A R B R A R B R C Similarly, R BC = R B R C R C R A R A R B R A and R CA = R C R A R A R B R B R C R B Delta to Star Transformation R AB B A R BC R A = Similarly, R B = and R C = RCA C B R B R AB R AC R AB R BC R CA R AB R BC R AB R BC R CA R AC R BC R AB R BC R CA A R A O RCA Resistance of a wire depends on its material and its size. It is given by C R C C where, ρ = Resistivity of a material in Ω cm l = Length of the wire, and A = Area of cross-section of wire. Self inductance (L) is the property of conductor (or coil) by virtue of which it opposes any change in direction or magnitude of current flowing through itself. It is given by L = Nφ henry l where, N = No. of turns in the coil φ = Flux set by current I. Also, L = µ 0 u r N A l henry Current through inductor is given by i (t) = t L dt or t L dt i(0) amp oltage across inductor is given by = L di dt = N dφ dt volt Power, P = I = LI di watt dt When n inductors are connected in series the equivalent inductance is = L... L n When n inductors are connected in parallel the equivalent inductance, =... L L n Relation between the mutual inductance and two coils with inductance and is given by relation. = k where 0 k where k = coefficient of coupling. It is a measure of amount of linking flux produced by one coil, w.r.t. other coil. Capacitance is the property of material by virtue of which it opposes the variation in potential between the two sides C = where, q = charge, = potential q R = ρl A C = ε 0 ε r A d
NETWORK AND SYSTES where C = Capacitance is proportional to the dielectric and area of the plates, and is inversely proportional to the distance between the plates. ε 0 = 8.86 0 F/m ε r = Relative permittivity A = Area of the plate d = Spacing between two plates. Current through the capacitor is i = C dv dt Amp. oltage across the capacitor is = C t i (t) dt or t C i(t) dt C (0) where C (0) = initial voltage on capacitor. When n capacitances are connected in series, the equivalent capacitance is given by C eq = C C C... C n When n capacitances are connected in parallel, the equivalent capacitance is given by C eq = C C C... C n Some conservation laws are given below : (a) The conservation of charge q = q and C = C ; i (b) (c) The conservation of flux linkage ψ = ψ and i = i ; The conservation of momentum P = P and m v = m v ; v F utual Inductance () It is the ability of one coil to produce an induced voltage in a nearby coil by electromagnetic induction, when the current being changed in the first coil, the action is vice-versa. It is measured in terms of the coefficient of mutual induction. GRAPH THEORY Network topology is only concern with the geometrical structure of the network. A graph of any Network can be drawn by placing all the nodes which are points of intersection of more than two branches. Consider a network given below : C C R R R L Given network Graph of the given network If there exists a path between every pairs of nodes of a graph, then the graph is said to be a connected graph. There are at least two branches in a circuit. Rank of graph = n, where n = no. of nodes or vertices. A subgraph is a subset of the branches and nodes of a graph. The subgraph is said to be proper if it consists of strictly have branches and nodes less than all the branches and nodes of the graph. Any tree contains n branches where n is the number of nodes or vertices. The branches in a tree called twig the branches other than the twig is called link (also called cords). 5 6 Corresponding tree 5 Given graph Tree Fig. : Simple graph and Tree In the above figure branches,, 5 are called twig while the branches,, 6 called link. Properties of Trees (i) In a tree, there exist one and only one path between any pair of nodes. (ii) Every connected graph has at least one tree. (iii) All the links of a tree together constitute the complement of the corresponding tree is called co-tree. (iv) Each tree has (n ) branches. (v) The rank of tree is (n ). This is also the rank of a graph to which the tree belongs i.e., both tree and graph has some rank. Where n is the number of nodes in a graph. (vi) No. of possible trees of a graph = dct [[A] [A T ]] where A is the reduced incidence matrix. If the total number of branches and nodes in a connected graph are b and n respectively, then the number of links l is given by l = b n Incidence atrix Tells information about the branches connected at which nodes and what the orientations relative to nodes. It is denoted by A a. The matrix obtained from Incidence atrix (A a ) by eliminating one of the rows is called the reduced incidence matrix denoted by A. It is of order (n ) a b where, n = No. of nodes b = Branches Properties of Complete Incidence atrix : (i) Sum of entries in any column is zero. (ii) The determinant of the complete incidence matrix of a closed loop is zero.
NETWORK AND SYSTES 5 Fundamental circuit or tie set matrix can be obtained by taking one link and other twigs at a time. The number of fundamental circuit depends upon the number of link. Consider a graph given below and select a tree. C a C h d C 5 6 Given graph Corresponding tree e 5 g f c b C Fig. : Formation of cut-set Fundamental loops = b n = No. of link Number of twig = n where, n = No. of nodes b = No. of branches The fundamental circuit can be drawn as : loop 5 loop 6 loop Since in the given graph there are 5 nodes, so 5 = cut-sets are possible. One thing should be kept in mind that the orientation of a cut-set is decided by the defining branch of the tree. Line four cut sets for the above choice of the tree are (a, c, b) ; (b, f, c) ; (c, g, d) ; (d, h, a) and each cut set defines a cut-set row vector. The cut-set (a, e, b), for example, defines the following cut-set row vector. Network shown below : Z Z Z In matrix form : fundamental Branches circuit 5 6 5 0 0 0 0 0 0 6 0 0 0 Cut-set matrix is formed by taking one twig and all other link. The set of branches which is cut by the closed line forms a cut set. Cut set separates the node of the given graph into two graphs. The no. of cut-set is equal to the no. of nodes. Cut-set containing only one twig are independent and are known as fundamental cut sets (f-cut sets) Number of cut-sets = Number of twig = n where n = No. of nodes in a graph. Consider a graph having 5 nodes shown below : a e 5 g f b c h Given graph d 5 Corresponding tree Note : Z Z T-Network Z Z 5 Z Z Ladder Network Z 6 Z Z π-network Z Z Z Z Bridge Network These network are said to be grounded or unbalanced network. Planar graph : It is possible to draw a graph on sheet of paper without crossing the lines then such types of the graph are said to be planar graph. Some of the planar graph is shown below : a b d c a d b Non-planar graph : If graph is drawn with crossing lines then it is called non-planar graph. Fig. shows the non-planar graph. (i) Non-planar graph c (ii) Non-planar graph
6 NETWORK AND SYSTES COUPLING Dot notation : Dot on the coils indicate the polarity of voltages induced in the coils. These also indicate whether the fluxes produced by the coils will be additive or opposing. (i) When coils are joined in series with fluxes additive, the equivalent inductance is = (i) agnetic Coupling : Consider two inductors with self inductances and, mutual inductance, and coefficient of coupling K and dots are shown in fig. applying KL to both side we get i (t) (t) i ( t) R i (t) R where, 0 K = K = (for opposing fluxes) and (t) = di (t) dt di (t) dt di (t) dt di (t) dt R i (t), R i (t) = 0 A transformer replaced by its T-equivalent : Coefficient of coupling : The amount of coupling between the inductively coupled coils is expressed in terms of the coefficient of coupling, which is defined as K = where, = mutual inductance between the coils = Self inductance of the first coil = Self inductance of the second coil agnetic adding : i i Coefficient of coupling, K is always less than unity. aximum value of or 00% called perfect coupling, when the entire flux of one coil links the other. The greater the coefficient of coupling between the two coils, the greater the mutual inductance between them and vice versa. K is a non negative number and is independent of the reference directions of the currents in the coils. If the two coils are a great distance apart in space, the mutual inductance in very small and k is also very small. K 0.99 Iron-core coupled circuits K varies between 0. to 0.8 for air core coupled circuits. (GATE 00) For better understanding the concept of the dot notation we must know the types of Coupling. Types of Coupling : (i) Electrical Coupling : Two coils are connected by a wire, so that physical connection exists. (ii) agnetic Coupling : Two coils are magnetically coupled but physically isolated, so called transformer coupling. agnetic opposition : i i i i i i (ii) Electrical Coupling : Case : When Coupled inductors in series : = = Case : Coupled inductors in parallel :
NETWORK AND SYSTES 7 Case : = = = = or L Transformer as an impedance matching device : l I:n l Z in N : N L Z L Z in = n = I I n There are three equivalent notations for a phasor. Polar form = m θ Rectangular form = m (cos θ j sin θ) Exponential form = m e jθ The cosine function can be written from the given Phasor. (t) = R e [ e jωt ] = R e [ m e jθ. e jωt ] (t) = R e [ m e j (ωt θ) ] = m cos (ωt θ). Both polar and exponential forms are used for the multiplication or division of two phasors, whereas rectangular form is used for addition and subtraction of two Phasors. Phasor Diagrams : RL Series Circuit : R ~ R I Power factor = RC Series Circuit : R ~ R I Power factor = RLC Series Circuit : L L = R L R θ θ = tan ( L / R ) cos θ (lagging) C C θ = R C θ = tan ( C / R ) R cos θ (leading) L R L R C I I and = N = n = I N I ~ R I C C and Z in = Z L n For L > C : L PHASORS AND PHASOR DIAGRAS : Phasor is a directed line segment, whose magnitude is the maximum value of the cosine function and angle is the initial phase of the cosine function. Phasor can be treated as complex number. When the circuit is analyzed using phasors, it is said to be in the frequency domain. θ ( L C) R C I
Gateway to PSUs (Electronics & Telecom, Electronics & Communication, Electrical, Electronics & Instrumentation) 0% OFF Publisher : Upkar Prakashan ISBN : 97887899 Author : Ashish Dixit Type the URL : http://www.kopykitab.com/product/099 Get this ebook