2009 Kurukshetra University B.E Electronics & Communication Engineering All ece 3rd sem papers Question paper
Paper : ECE-203(E)
Time : Three hours
Maximum Marks : 100
Note : Attempt any five questions.All questions carry equal marks.
1.(a) Discuss noise in FM reception.
(b)Explain the various sources of noise.
2.(a)What is SSB modulation? Explain the benefits of using SSB modulation.
(b)Explain Phase discrimination method.
3.(a)Describe Phase-locked looped demodulator.
(b)An FM wave is applied to a square-law device with output voltage V2 related to input voltage V1 by V2=a(V1square) where 'a' is a constant. Explain how such a device can be used to obtain an FM wave with a greater frequency deviation than available at the input.
4.(a)Explain the tracking and alignment of receivers.
(b)Explain the block diagram of AM transmitter.
5.(a)Derive mathematical representation of random noise.
(b)Explain the noise in reactive circuits.
6.(a)Derive power relations in AM wave.
(b)Explain the spectrum of AM wave.
7.(a)Draw the circuit diagram of a ratio detector and explain its operation. How is amplitude limit obtained in this detector?
(b)Compare FM and PM signals.
8.Write short notes on the following :
(c) TRF receivers
ELECTROMECHANICAL ENERGY CONVERSION
PAPER : ELE-201(E)
Time : Three Hours Maximum Marks : 100
Note : Attempt Five questions,selecting at least one question from each unit.All questions carry equal marks.
1.Discuss the magnetic materials generally used in electrical machines.With the help of diagrams,discuss the constructional details of a single phase transformer.Develop its E.M.F. equation.
2.Discuss various tests required to determine the equivalent circuit parameters of a transformer.
3(A).Develop the expression for energy and force in a singly excited magnetic field system.
(B).With the help of neat diagram,explain the procedure to determine the magnetic characteristics of a d.c shunt machine
4.Develop the expression for generated e.m.f in a d.c. generator.Explain the e.m.f build-up in a d.c. shunt generator.
5.Develop the expression for torque for a three-phase induction motor.Draw and explain its torque-slip characteristics.
6.Explain the ways to control the speed of three-phase induction motors.
7.Define voltage regulation for an alternator.Give its importance.List the various methods and discuss the m.m.f method to determine voltage regulation.
8.Discuss V-curves and starting of synchronous motors.
paper : ECE-203(E)
TIME:THREE HOUR] MAXIMUM MARKS:100
NOTE: (i) ATTEMPT ANY FIVE QUESTIONS.
(II)ALL QUESTIONS CARRY EQUAL MARKS.
1. (a) Explain the various classification of noise. 10
(b) Derive an expression for equivalent noise temperature of a cascade of networks
in terms of their individual equivalent noise temperatures. 10
2. (a) Explain the coherent detection of DSBSC waves. 10
(b) What is VSB modulatin and benfits of using VSb modulation ? 10
3. (a) Explain the Pre-emphasis and de-emphasis in FM. 10
(b) DEscribe Phase locked looped demodulator. 10
4. (a)Explain Radio telephone transmitter. 10
(b) What do you mean by Supehetrodyne receivers? 10
5. (a) What is SSB and benifits of using SSB modulation ? 10
(b) Explain the block diagram of AM transmitte. 10
6. (a) what is the effect of noise on carrier ? 10
(b) What is noise triangle ? 10
7. (a) Explain square law modulation methods. 10
(b) what do you mean by Diode dector with filters ? 10
8. Write short notes on the foloowing :
(a) AFC. 6
(b) Narrow Band noise. 7
(c) Frequency scintillation. 7
SEMICONDUCTOR DEVICES AND CIRCUITS
Time: Three Hours
Note: Attempt five questions, selecting at least one question from each unit.
1. (a)Explain the photoelectric effect. What are various devices based on this principle ? Explain the working of photo-voltaic cell. 
(b) Explain the working of a full wave bridge rectifier with suitable waveforms. 
2. (a) A half wave rectifier uses a transformer ratio 2: 1. The load resistance is 500 ohms. If the primary voltage is 240 V (rms), find the d.c. output voltage and peak inverse voltage. 
(b) What are the various parameters to design a power supply. Explain the working principle of SMPS with suitable diagrams. 
3. Explain the following:
(a) Operating point of transistor. 
(b) Comparsion of transistor action in CB, CC and CE configurations. 
(c) Biasing of transistor. 
(d) Emitter follower. 
4. (a) What are the various limitations for BJT to operate a high frequencies ? How these can be eliminated ? 
(b) A transistor is operating in CE configuration, in whici Vcc = 8 V, and voltage drop across resistance R connected in collector circuit is 0.5 V The value of Rc = 800 ohms.If alpha = 0.96, determine the (i) collector emitter voltage, and (ii) base current.
5. (a) Why feedback is required in amplifiers ? What is the effect of feedback on bandwidth, input and output resistance. Derive the relations. 
(b) Draw and explain the circuit of phase shift oscillator .What is the frequency of oscillations ? 
6. (a) Explain and compare various feedback topologies used.
(b) What are the various power amplifiers ? Classify ther and compare their characteristics. 
7. (a) Compare JFET with BJT. 
(b) In an n-channel JFET biased by potential divide method, it is desired to get ID = 2.5 mA and VDS = 8 V.If VDD = 1 M ohms and R2 = 500 k ohms, find the value of RS. The parameters of JFET are IDSS = 10 mA an Vp = -5 V. 
8. Write short notes on the following:
(a) V-MOSFET. 
(b) MOSFET in Enhancement modes. 
Semiconductor Devices and Circuits
Time: Three Hours
Maximum Marks: 100
Note :- Attempt any Five questions. All questions carry equal marks.
1.(a) What is regulated power supply ? Draw its block diagram and give function of each block. 
(b) What is meant by TUF of a rectifier ? Derive its value for half wave and bridge rectifier. 
2.(a) Show that the maximum d.c. output power in a half wave circuit occurs when the load resistance equals the diode resistance RF 
(b) (i) For what voltage will the reverse in a p-n junction Ge diode reach 90% of its saturation value at room temperature ? 
(ii) What is the ratio of the current for a forward bias of 0 05 V to the current for the same magnitude of reverse bias. 
(iii) If the reverse saturation current is 10 micro A, calculate the forward currents for voltages of 0.1, 0.2 and 0.3 V respectively. 
3. (a) Sketch two RC-coupled CE transistor stages. Show the low freq. model for one stage. What is the expression for fL ? 
(b) Given :
IE = 2.5 mA,
hfe = 140,
hoe = 20 micro S (micro mho) and
hob= 0 5 micro S
—the common emitter hybrid equivalent ckt— the common base Re model. 
4.(a) Draw fixed bias ckt. Explain why the circuit is unsatisfactory if the transistor is replaced by another of the same type. 
(b) In a certain transistor 99 6% of the carriers injected into the base cross the collector base junction. If the leakage current is 5 micro A and the collector current is 20 mA. Calculate at alpha d.c. and the emitter current. 
(c) What is sensistor ? Explain how it can be employed in a transistor ckt. to compensate the variation of operating point with temperature. 
5.(a) What do you mean by voltage amplifier and current amplifier ? Give their equivalent ckt. 
(b) Classify amplifiers based on Sting point selection. Compare various configurations in terms of efficiency and distortion. 
(c) For a class B amplifier providing 20 V peak signal to a 16 ohm load (speaker) and a power supply of Vcc = 30 V. Determine the input power, output power and ckt. efficiency. 
6.(a) Draw the ckt. diagram of a crystal oscillator and explain its operation in detail. 
(b) Discuss the advantages add limitations of a resonant ckt. sinusodial oscillator. 
7.(a) Explain two biasing circuit for JFET. Explain under what circumstances each of these are used. 
(b) Define transconductance, drain resistance and amplification factor of a FET and derive the relation between them. 
8.(a) Distinguish between depletion and enhancement MOSFET. 
(b) (i) A JFET has a drain current of 6 mA if
IDSS = 12 mA and
Vp = - 4 V find VGS. 
(ii) Por an n-channel FET
IDSS = 5.8 mA,
Vp = 3 V and
VGS = -2 V
find ID, gm, gmo 
Electromechanical Energy Conversion Paper
Time: Three Hours
Maximum Marks: 100
Note:—Attempt any FIVE questions.
1.(a) State Faraday's laws of electro-magnetic induction and explain how it is applied for working of a d.c. motor. 
(b) Discuss the various types of Losses in magnetic circuits. 
2.(a) Draw the no-load phasor diagram of a transformer and derive expression for magnetizing and core-loss components of no-load current. 
(b) Define the voltage regulation of a transformer. Deduce the expression for the voltage regulation. 
3.(a) What is an electromechanical conversion device ? Explain the working of a generator with the help of a power flow diagram. 
(b) Explain how torque is produced in a rotating electrical machine. What do you understand by torque angle ? 
4.(a) Derive the expression for generated emf in a d.c generator. Define all the symbols with their units. 
(b) Discuss the effects of armature reaction in a d.c. generator. 
5.(a) What is meant by back emf ? Is the back emf greater or lesser than the applied voltage ? Why ? By what amount do the two voltage differ ? 
(b) Discuss the flux central method for the speed of a shunt motor. 
6. Discuss the point of similarities betweeh a transformer and an induction motor. Hence, explain why an induction machine is call a generalized transformer ? Why an induction motor, at no-load,operates at a very low power factor ? 
7.(a) Draw the torque-speed characteristics of polyphase induction motor and clearly indicate the effect of change in rotor resistance. 
(b) Explain the terms slip, slip frequency, wound rotor and cage rotor. 
8. Write short notes on the following:—
(a) Starting of Synchronous motor. 
(b) Curves of Synchronous motor. 
Time: Three Hours
Maximum Marks: 100
Note: Attempt any FIVE questions
1. (a) Define abstract data type and give any three applications of ADTS. 
(b) Wnte an algorithm which translates a POSTFIX expression to an INFIX expression. 
(c) Show with an example how a UNION is implemented Also differentiate between a UNION and a STRUCTURE in C. 
2. (a) Show with an example how an array is passed as a parameter in C. 
(b) What are the main types of PRIORITY QUEUES ? Explain each one in detail. 
(c) Show how to implement three stacks in one array. 
3. (a) What are the advantages and disadvantages of representing a group of items as an array versus a linear line list? 
(b) What are the steps to inserting a new item at the head of a linked list ? Use one short English sentence for each step. 
Write a program to swap two adjacent elements by adjusting only the pointer (and not the data) using:
(i) Singly linked lists. 
(ii) Doubly linked lists. 
4.(a) Explain in detail why dynamic data structures are needed. 
(b) What are the three primitive operations that can be applied to Queues ? Explain briefly. 
(c) Write an algorithm to reverse the order of items on a list. Prove that your algorithm works correctly. 
5.(a) Explain the following:
(i) STRICTLY binary tree. 
(ii) Complete binary tree. 
(iii) Almost complete binary tree. 
(b) The order of nodes of a binary tree id PREOROER and INORDER Traversal are as under :
PREORDER—B C E D F A G H.
INORDER —A B C D E F G H.
Draw the corresponding Binary Tree. 
(c) Two binary trees are similar if they are both empty or both non empty and have similar left and right subtrees. Write a function to decide whether two binary trees are similar. 
6.(a) Write a note on:
(i) Efficiency of Binary Search tree operations.
(ii) Balanced trees. 
(b) Write an algorithm to find Kth element of a list represented by a tree and also show that the number of tree nodes examined in finding the Kth list element is less than or equal to 1 more than the depth of the tree. 
(c) What are the broad categories of non-binary trees ? Describe any one in detail. 
7.(a) Write a non-recursive depth first traversal algorithm for graphs. 
(b) Explain Prim's algorithm in detail. . 
8.(a) What is the purpose of hashing ? Describe any one method used to handle collisions in hashing. 
(b) Sort the lists 3, 1, 4, 1. 5 , 9, 2 ,6, 5, 3, 5, 8, 9, 7 using any one of them:
(ii) Quicksort. 
Maximum Marks : 100
Note:—Attempt five questions in all, selecting at least one question from each Section.
1.(a) A receiver having overall voltage gain A, output resistance RL & bandwidth B operates at temperature T oK. The receiver input resistance is Rr and it is fed from an antenna having resistance Ra. Derive a formula for noise power No. Also find the value of noise figure F in terms of Ra, Rt and Req, where Req is the equivalent noise resistance excluding RT 
(b) The noise output of a resistor is amplified by a noiseless amplifier having gain of 60 and bandwidth of 90 kHz. A meter connected to the output of the amplifier reads 1.2 mV rms. (i) If the resistor is operated at 17 oC what is its resistance ? (ii) If the bandwidth of the amplifier is reduced to 10 kHz, its gain remaining constant, what will the meter read now ? 
2. (a) What are the various sources of noise ? 
(b) Define noise bandwidth. What is the relation between noise bandwidth BN and noise power PO at the output of a system ? 
(c) Give the mathematical Presentation of noise. 
SECTION - II
3.(a) What is modulation ? Why is it required to modulate a signal before transmission ? 
(b) Find an expression for the instantaneous voltage of an amplitude modulated signal. Draw the waveforms for amplitude modulated signal; also describe the power relations involved in AM. 
(c) Compare DSBSC-AM and SSB-AM. 
4.(a) With the help of suitable diagrams and waveforms describe the square law diode modulation system. 
(b) Explain the working of a linear diode detector. 
(c)The rms value of a carrier voltage after amplitude modulation to a depth of 40% by a sinusoidal modulating voltage is 55 V. Calculate the rms value of can ier voltage when it is modulated to a depth of 80%. 
5.(a) In a FM system if mf is doubled by halving the modulating frequency, what will be the effect on maximum deviation ? 
(b) Explain the spectrum of a frequency modulated signal and compare it with that of amplitude modulated signal. 
6.(a) What is the principle of operation of slope detectors ? Explain in detail the working of a balanced slope detector. 
(b) What is pre-emphasis and why is it required ? 
(c) Differenaate between WBFM and NBFM. 
7.(a) Draw and explain the complete block diagram of Armstrong frequency modulation system in what circumstances can we dispense with the mixer ? 
(b) Explain radio telephone transmitter highlighting its special features like volume compressors, VODAS and privacy devices. 
8.(a) Discuss the merits of delayed AGC as compared to simple AGC. Show AGC curves to illustrate the comparison and explain how delayed AGC may be obtained an applied.
(b) Explain with block diagram the functioning of a TRF receiver. 
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