Written Examination for selection into Ph. D registration under Utkal University-2012

Nodal Centre: IGIT, Sarang, Dhenkanal.

Stream: ELECTRICAL ENGINEERING

Instruction: A candidate has to answer 30 multiple type questions in 30 minutes. Each question carries 4 marks. There is no negative marking for wrong answers. The candidate has to encircle only the correct (most appropriate) answer out of the four (a), (b), (c) and (d) choices given. Putting any mark other than the circle mark or encircling more choices or answering in any ambiguous manner will invite ZERO mark on evaluation. TIME: 30 MINUTES; FULL MARKS: 120 1. A three-phase synchronous machine of negligible stator resistance is under floating

condition after being synchronized with the infinite bus. State the next operating step required to force the machine to act as a synchronous generator and share the grid load.

(a) Increase the excitation of the machine (b) Decrease the excitation of the machine (c) Increase the mechanical input to the prime mover (d) Decrease the mechanical input to the prime mover

2. A three-phase cylindrical rotor synchronous motor, fed from an infinite bus, is operating

at unity power factor while driving its rated full load. What will be the nature of its operating power factor if the load on its shaft is reduced to 70% of its full load without changing its excitation? Neglect the stator resistance. (a) Lagging with power factor close to 0.9 (b) Lagging with power factor close to zero

(c) Leading (d) Unity

3. The per-phase direct axis and the quadrature axis synchronous reactances of a grid-

synchronized three-phase salient pole synchronous generator supplying full load rated current at 0.95 lagging power factor are 0.88 per unit and 0.52 per unit respectively. The stator resistance of the machine can be neglected. The excitation of the machine is kept unaltered. What is the per-unit no-load induced emf per phase along with its load angle? (a) 1 p.u. with a load angle of 18.2 degree approximately (b) 1.4 p.u. with a load angle of 71.8 degree approximately (c) 1.5 p.u. with a load angle of 23.02 degree approximately

(d) 1 p.u. with a load angle of 20.02 degree approximately

4. A balanced three-phase induction motor has an efficiency of 88% when its output is 60 kW. At this load, both the stator and rotor copper losses are identical and each of these losses individually equals to the stator core loss. The rotor core loss can be neglected. The mechanical losses are 25% of the no-load loss. What is the ‘slip’ of the motor under this operating condition? (a) 0.083793 (b) 0.038793 (c) 0.073893 (d) 0.093873

5. If the excitation of a grid-connected three-phase synchronous motor operating at unity power factor and driving a certain mechanical load on its shaft is increased by 10%, then its stator input current will (a) increase (b) remain same (c) decrease (d) decrease by 10%

6. Consider the following statements regarding a first order system with a proportional (P) controller which exhibits an offset to a step input: In order to reduce the offset, it is necessary to

i. increase the gain of the P controller ii. add derivative mode

iii. add integral mode

(a) i, ii and iii (b) i and ii (c) ii and iii (d) i and iii

7. Which of the following are the characteristics of a hydraulic actuator? i.sluggish ii.having capacity to handle large power

iii.having linear operation

(a) i, ii and iii (b) i and ii (c) ii and iii (d) i and iii

8. Which of the following analytical methods are applicable to sampled data system? i. Modified Z-Transformation ii. Shanon’s Theorem iii. State Transition Matrix iv. Nyquist Plot (a) i, ii, iii and iv (b) iii and iv (c) i and ii (d) i, ii and iii

9. The winding factor of a full-pitched narrow phase spread winding is

(a) 0.855 (b) 1.0 (c) 0.955 (d) 0.9

10. In case of a synchro error detector, the electrical zero position of control transformer is obtained when angular displacement between rotors is (a) Zero (b) 45 degreeq (c) 90 degree (d)180 degree

11. For a discrete time sequence with finite unit sample response ,22, nnh a finite duration input signal sequence 61, nnx produces output that is nonzero in the interval

a) 62 n b) 41 n c) 83 n d) 110 n

12. For input sequence x(n), y(n) is the output sequence for a system. Which of the following systems is linear, time-variant and causal?

a) )()( 2nxny b) 10),(1)( ynxnyny c) )()( nnxny d) )()( nxny

13. Step response of the causal system described by the difference equation nxnyny 1 is

a) nun1 b) nnu c) nun 1 d) nnun1

14. Given two 4-point sequences x(n)=[4, 3, 2, 1] and h(n) =[1, -1, 0, 0], their 4-point circular convolution, y(n) is

a) [-3, 1, 1. 1] b) [3, -1, -1. -1] c) [3, 1, -1. 1] d) [1, 1. 1, -3]

15. A two stage amplifier with two identical and non-interacting stages is required to have an upper cut off frequency of 3 MHz and lower cut off frequency of 30 Hz. What should be the upper and lower cut off frequency of individual stages (most appropriate answer)?

a) 2 MHz & 50 Hz respectively b) 4 MHz & 20 Hz respectively c) 5 MHz & 20 Hz respectively d) 5 MHz & 50 Hz respectively

16. An amplifier with open loop gain of -1000 and feedback factor β= -0.1 had a gain change of 20 % due to temperature. What would be change in gain of feedback amplifier?

a) 1 % b) 2 % c) 0.1 % d) 0.2 %

17. The tilt P and rise time rt for the output waveform of an amplifier, with square wave as the input, are related to upper cut off frequency Hf and lower cut off frequency Lf of the amplifier as follows

a) P is inversely proportional to Lf and rt is proportional to Hf b) P is inversely proportional to Hf and rt is proportional to Lf c) P is proportional to Lf and rt is inversely proportional to Hf d) P is proportional to Hf and rt is inversely proportional to Lf

18. An EX-OR gate is to be built with NAND gates only. The minimum number of 2- input NAND gates required is

a) 3 b) 4 c) 5 d) 6

19. An 8 input MUX is to be built with a tree network of 2 input MUXs. The number of 2 input MUXs required is

a) 4 b) 8 c) 6 d) 7

20. While computing N-point discrete point DFT, the phase factor is defined as Nj

N eW /2 . Then which of the following is not true for an integer value of K ?

a) KN

NK

N WW

2 b) K

NNK

N WW

c) 22NK

N

NK

N WW

d) K

NK

N WW2

2

21. The unit impulse response of a system is given as c (t) = 4 e – t + 6 e – 2t. The step

response of the same system for t 0 is equal to:

a) – 3 e – 2t + 4 e – t + 1 b) – 3 e – 2t – 4 e – t + 1 c) – 3 e – 2t + 4 e – t + 1 d) – 3 e – 2t – 4 e – t + 7

22. For the arrangement shown in Fig. below, the circuit is initially in steady state with thyristor T off. After thyristor T is turned on, the peak thyristor current would be

a) 2 A

b) 22 A

c) 40 A

d) 42 A

23.A step up chopper is fed from a 200V dc source to deliver a load voltage of 600V. If

the non-conduction time of thyristor is 100 sec, the required pulse width will be

a) 100 sec

b) 200 sec

c) 220 sec

d) 660 sec

24. In a two plant system, the load is connected at plant no. 2. The loss coefficients

a) B11 and B22 are nonzero but B12 is zero

b) B11, B12 and B22 are nonzero

c) B11 and B12 are nonzero but B22 is zero

d) B11 is nonzero but B12 and B22 is zero

25. If the penalty factor for bus 1 in a two-bus system is 1.25 and if the incremental cost of production at bus 1 is Rs. 200 per MWh, the cost of received power at bus 2 is

a) Rs. 250 / MWh b) Rs. 62.5 / MWh c) Rs. 160 / MWh d) None of the above

26. The capacitance and inductance per unit length of a line operating at 110 kV are 0.01 microfarad and 2 mH. The surge impedance loading of the line is

a) 40 MVA b) 30 MVA c) 27 MVA d) None of the above

27. An alternator of 300 kW is driven by a prime mover of speed regulation 4% and another alternator of 200 kW driven by a prime mover of speed regulation 3%, the total load they can take is

a) 500 kW b) 567 kW c) 425 kW d) 257 kW

28. In a type A chopper, source voltage is 100 V DC, on period = 100 sec, off period =150 sec and RLE load consists of R = 2 ohm, L = 5 mH and E =10 V. For continuous conduction, determine the values of average output voltage. (a) 66.66 V (b) 56.66 V (c) 100 V (d) 191 V 29. A three-phase full wave controlled rectifier feeds a separately excited dc motor. The data are Td = 140 Nm, Ia =60 A and ωm = 65 rad/s. With these data, the back emf of the motor will be nearly (a) 102 (b) 178 (c) 152 (d) 194 30. In a dc drive supplied by a single-phase ac source and a rectifier, discontinuous conduction can be avoided by (a) decreasing the frequency of the ac supply (b) adding a capacitor in series with the armature of the dc motor (c) increasing the frequency of the ac supply (d) adding an inductor in series with the armature of the dc motor ---------------------------x------------------------

PhD Entrance Test-2012(Electronics & Telecommunication

Engineering)

Utkal University

Nodal center: IGIT

Full mark: 120

Time: 1 hr

Name of the candidate:

(All questions carry equal marks)

SET A

1. A complex bandpass signal has a bandwidth of 200 kHz. What is the minimum

sampling rate for this signal?

a) 200 kHz

b) Cannot be determined

c) 400 kHz

d) 800 kHz

2. The advanced mobile phone system (amps) uses two bands. The first band of 824

to 849 MHz is used for sending, and 869 to 894 MHz is used for receiving. Each

user has a bandwidth of 30 kHz in each direction. The 3-kHz voice is modulated

using FM, creating 30 kHz of modulated signal. How many people can use their

cellular phones simultaneously assuming 33 channels used for control?

a) 790

b) 800

c) 820

d) 750

3. An analog voltage is in the range of 0 to 8 v is divided in eight equal intervals for

conversion to 3-bit digital output. The maximum quantization error is

a) 0 V

b) 1 V

c) 0.5 V

d) 2 V

4. A C program contains the declaration and initial assignments:

int i = 8, j =5

float x = 0.005, y = - 0.01;

char C = ‘C’ , d = ‘d’;

the values of arithmetic expression (2*(i/5) + (4*j-3)) % (i=j-2) is

a) 18

b) 15

c) 10

d) 17

5. In a 8085 microprocessor, the following sequence of instructions is executed:

STC

CMC

MOVE A,B

RAL

MOVE B,A

After the last instruction, the output will

(a) Rotate the contents of the accumulator and store it in B

(b) Get the contents of B register into accumulator and rotate it to left by one bit.

(c) Double contents of B register

(d) Manipulate carry in A and B

6. OC- 48 is a network line with transmission speeds of approximately equal to

a) 10 Gbps

b) 51.84 Mbps

c) 40 Gbps

d) 2.5 Gbps

7. A 741 op amp has a rise time of 0.35 micro-second. Find the small-signal or

unity-gain bandwidth.

a) 10 MHz

b) 1 MHz

c) 5 MHz

d) 20 MHz

8. A transmission line of characteristic impedance Zo = 50 ohms, phase velocity vp =

2*108 m/s, and length l = 1m is terminated by a load Zl = (30-j40) ohms. The

input impedance of the line for a frequency of 100 MHz will be

a) (30+j40) ohms

b) (50-j40) ohms

c) (30+j60) ohms

d) (30-j40) ohms

9. We need to send data at a 1-Mbps rate. What is the minimum required bandwidth

using a combination of 4B/5B and NRZ-I or Manchester coding ?

a) 625 kHz and 1 MHz

b) 500 kHz and 2 MHz

c) 500 kHz and 1 MHz

d) 625 kHz and 1.5 MHz

10. What are the propagation time and the transmission time for a 2.5-kbyte message

if the bandwidth of the network is 1Gbps ? The distance between the sender and

receiver is 12,000 km and that light travels at 2.4 x 108 m/s

a) 100 ms and 0.02 ms

b) 100 ms and 0.01 ms

c) 50 ms and 0.02 ms

d) .02 ms and 50 ms

11. For input sequence x(n), y(n) is the output sequence for a system. Which of the

following systems is linear, time-variant and causal?

a) )()( 2nxny

b) 10),(1)( ynxnyny

c) )()( nnxny

d) )()( nxny

12. If a discrete time system is described by input and output equation

nxnxHny )( , the system is

a) Causal, time variant, and linear

b) Non-causal, time invariant, and linear

c) Non-causal, time variant, and linear

d) Causal, time invariant, and non-linear

13. While computing N-point discrete point DFT, the phase factor is defined

as Nj

N eW /2 . Then which of the following is not true for an integral value

of K ?

a) K

N

NK

N WW

2

b) K

N

NK

N WW

c) 22

NK

N

NK

N WW

d) K

N

K

N WW2

2

14. A two stage amplifier with two identical and non-interacting stages is required to

have an upper cut off frequency of 3 MHz and lower cut off frequency of 30 Hz.

What should be the upper and lower cut off frequency of individual stages (most

appropriate answer)?

a) 2 MHz & 50 Hz respectively

b) 4 MHz & 20 Hz respectively

c) 5 MHz & 20 Hz respectively

d) 5 MHz & 50 Hz respectively

15. An amplifier with open loop gain of -1000 and feedback factor β= -0.1 had a gain

change of 20 % due to temperature. What would be change in gain of feedback

amplifier?

a) 1 %

b) 2 %

c) 0.1 %

d) 0.2 %

16. What is the output voltage ov of the OpAmp circuit shown in the following

figure:

a) -25 volt

b) volt12

c) volt12

d) 0 volt

17. The tilt P and rise time rt for the output waveform of an amplifier, with square

wave as the input, are related to upper cut off frequency Hf and lower cut off

frequency Lf of the amplifier as follows

a) P is inversely proportional to Lf and rt is proportional to Hf

b) P is inversely proportional to Hf and rt is proportional to Lf

c) P is proportional to Lf and rt is inversely proportional to Hf

d) P is proportional to Hf and rt is inversely proportional to Lf

18. A PCM system uses a uniform quantizer followed by a 7 bit binary encoder. The

bit rate of the system is equal to50 megaBits per second (Mbps). What is the

maximum message bandwidth for which the system operates satisfactorily?

a) 7.14 MHz

b) 3.57 MHz

c) 0.28 MHz

d) 0.14 MHz

19. An OP Amp has slew rate of 5 Volt/ Sec. The largest possible amplitude of

sinusoidal output voltage is

a) 10 volts

b) 5 volts

c)

5 volts

d) 2

5 volts

20. An 8 input MUX is to be built with a tree network of 2 input MUXs. The number

of 2 input MUXs required is

a) 4

b) 8

c) 6

d) 7

21. The Doppler Effect is used in

a) MTI radar system

b) FM radar system

c) Both a and b

d) Crystal oscillator

22. Gain margin is the reciprocal of the gain at the frequency at which the phase

margin is?

a) 0

b) 90

c) -90

d) 180

23. When electromagnetic waves are propagated in a waveguide

a) They travel along the border walls of the guide

b) They are reflected from the walls but do not travel along them

c) They travel through the dielectric without touching the walls

d) They travel along all four walls of the waveguide

24. For separating channels in FDM receivers

a) Band pass filters are used.

b) Band stop filters are used

c) Differentiators are used.

d) Integrators are used.

25. An antenna to be used for a band of frequencies ranging from 60 to 65 MHz was

designed for 65 MHz. The tuning element required is

a) A variable inductance

b) A fixed capacitance

c) A variable capacitance.

d) none of these

26. The transmission line whose characteristic impedance is 300 Ω is used to inter-

connect the receiving antenna and the receiver input. Reflection coefficient of ¼

is observed on the line. The impedance of the load is

a) 75 Ω

b) 200 Ω

c) 500 Ω.

d) none of these

27. The maximum power efficiency of an AM modulator is

a) 78.5%

b) 50%

c) 85%

d) 100%

28. A 10 KW transmitter is modulated to 80%.The average sideband power will be

a) 1.80KW

b) 8KW

c)3.2KW

d) 4.6KW

29. A shift counter comprising of five Flip Flops with an inverse feedback from the

output of the MSB Flip Flops to the input of the LSB Flip Flop is a

a) Divided by 32 counter

b) Divided by 10 counter

c) 5 bit shift register

d) Modulus -5 counter

30. The base width in a junction transistor is deliberately chosen small so that

a) The electric field is large

b) The concentration gradient of injected carriers is small

c) To reduce recombination of injected minority carriers

d) The majority carriers easily reach the collector

BEST OF LUCK

1

Written Test for PhD

Subject: Computer Science Date : 22.02.2013

Time: 10.00 a.m to 11 a.m

Name of the Candidate:

Qualification:

Subject of Research:

Signature of the candidate with date:

Instruction: The question paper contains total of 30 numbers of questions. Each question

carries 4 marks. There is no negative mark. The candidate is required to score minimum of 50%

of total 120 marks, i.e. 60 marks, which is to be considered as qualifying marks. Answer all

questions. Each question is having four alternative answers as given immediately after each

question labeled as A, B, C and D. Encircle only one alternative with blue coloured ball point

pen which you would think as the most appropriate alternative for correct answer. Overwriting

or encircle of more than one answer is liable for wrong answer for which no credit may be

given.

Q1. If the address of A[1][1] and A[2][1] are 1000 and 1010 respectively and each element occupies 2 bytes

then the array has been stored in _________ order.

A. Row Major B. Column major C. Matrix major D. None of these

Q2. A class of language that is closed under

A. union and complementation has to be closed under intersection

B. intersection and complement has to be closed under union

C. union and intersection has to be closed under complementation

D. both (A) and (B)

Q3. Consider the following type definition.

typedef char x[10]; x myArray[5];

What will sizeof(myArray) be ? (Assume one character occupies 1 byte)

A. 15 bytes B. 10 bytes C. 50 bytes D. 30 bytes

2

Q4. A girl counted in the following way on the fingers of her left hand : She started by calling the thumb 1,

the index finger 2, middle finger 3, ring finger 4, little finger 5 and then reversed direction calling the

ring finger 6, middle finger 7 and so on. She counted upto 1994. She ended counting on which finger ?

A. Thumb B. Index finger C. Middle finger D. Ring finger

Q5. (P v Q) ^ (P→R) ^ (Q → R) is equivalent to

A. P B. Q C. R D. True = T

Q6. In how many different ways can the letters of the word 'DETAIL' be arranged in such a way that the

vowels occupy only the odd positions?

A. 32 B. 48 C. 36 D. 60

Q7. The time complexity of an algorithm T(n), where n is the input size,is given by

T( n) = T( n - 1) + 1/n if n > 1. The order of this algorithm is

A. log n B. n C. n2 D. n

n

Q8. A text is made up of the characters a, b, c, d, e each occurring with the probability .12, .4, .15, .08 and

.25 respectively. The optimal coding technique will have the average length of

A. 2.15 B. 3.01 C. 2.3 D. 1.78

Q9. For the same problem the code size in KLOC in various language can be best estimated at Assembly

language: OO languages : icon based graphical language as

A. 1:10: 100 B. 100: 10:1 C. 1:20: 20 D. 1: 1:2

Q10. A scheduling algorithm assigns priority proportional to the waiting time of a process. Every process

starts with priority zero(the lowest priority). The scheduler re-evaluates the process priorities every T

time units and decides the next process to schedule. Which one of the following is TRUE if the

processes have no I/O operations and all arrive at time zero?

A. This algorithm is equivalent to the first-come-first-serve algorithm.

B. This algorithm is equivalent to the round-robin algorithm.

C. This algorithm is equivalent to the shortest-job-first algorithm.

D. This algorithm is equivalent to the shortest-remaining-time-first algorithm.

Q11. P, Q, R are three languages, if P and R are regular and if PQ = R, then

A. Q has to be regular B. Q cannot be regular

C. Q need not be regular D. Q cannot be a CFL

3

Q12. What is the return value of f(p,p), if the value of p is initialized to 5 before the call? Note that the first

parameter is passed by reference, where as the second parameter is passed by value.

int f(int &x, int c) { c = c-1; if(c= =0) return 1; x = x+1; return f(x,c) *x; }

A. 3024 B. 6561 C. 55440 D. 161051

Q13. Following context free grammar

S —> aB | bA

A —>b | aS | bAA

B —> b | bS | aBB

generates strings of terminals that have

A. equal number of a's and b's B. odd number of a's and odd number b's

C. even number of a's and even number of b's D. odd number of a's and even number of a's

Q14. Which of the following is TRUE?

A. Every relation in 3NF is also in BCNF

B. A relation R is in 3NF if every non-prime attribute of R is fully functionally dependent on every

key of R

C. Every relation in BCNF is also in 3NF

D. No relation can be in both BCNF and 3NF

Q15. Consider the following program segment

d = 0;

for(i = 1; i < 31; ++i)

for(j = 1; j < 31; ++j)

for(k = 1; k < 31; ++k)

if(((i + j + k) % 3) = = 0)

d = d + 1;

printf("%d", d );

The output will be

A. 9030 B. 27000 C. 3000 D. none of the above

4

Q16. Consider the join of a relation R with relation S. If R has m tuples and S has n tuples, then the

maximum size of join is:

A. mn B. m+n C. (m+n)/2 D. 2(m+n)

Q17. An instance of relational schema R (A, B, C) has distinct values of A including NULL values. Which

one of the following is true?

A. A is a candidate key B. A is not a candidate key

C. A is a primary Key D. Both (A) and (C)

Q18. Which one of the following is not true for a view:

A. View is derived from other tables. B. View is a virtual table.

C. A view definition is permanently stored as part of the database.

D. View never contains derived columns.

Q19. The smallest integer than can be represented by an 8-bit number in 2’s complement form is

A. -256 B. -128 C. -127 D. 0

Q20. (P v Q) ^ (P → R )^ (Q →S) is equivalent to

A. S ^ R B. S → R C. S v R D. All of above

Q21. In a time - division switch, which governs the destination of a packet stored in RAM?

A. TDM bus B. Crosspoint C. Crossbar D. Control unit

Q22. The functionally complete set is

. ^ v B. ↓ ^ C. ↑ D. None of these

Q23. A group of 2m - 1 routers are interconnected in a centralized binary tree with router at each tree node.

Router I communicates with router J by sending a message to the root of the tree. If root then sends the

message back down J, the mean path length will be

A. 2 (m - 2) B. 2 (2m - 1) C. m - 1 D. (2m - 1)/mJ

Q24. A circuit switching network has the following characteristics :

Set up time = 5 sec; Propagation = 5 sec; Message size = 1 M bits;

Data transmission rate = 1 M bits; Data transmission rate = 1Kbps ; Number of hops = 10

When will the last bit of the message reach the receiver?

A. t = 520 sec B. t = 1000 ms C. t = 250 sec D. t = 1025 sec

5

Q25. For the same functionality coding in C vs coding in assembly language yields code in LOC which is

A. three times larger B. times smaller C. 10 times smaller D. same size

Q26. The amount of ROM needed to implement a 4 bit multiplier is

A. 64 bits B. 128 bits C. 1 Kbits D. 2 Kbits

Q27. In the IPv4 addressing format, the number of networks allowed under Class C addresses is

A. 214

B. 27 (C) 2

21 (D) 2

24

Q28. A primary key if combined with a foreign key creates

A. Parent-Child relationship between the tables that connect them.

B. Many to many relationship between the tables that connect them.

C. Network model between the tables that connect them.

D. None of the above.

Q29. Which of the following gates would output 1 when one input is 1 and other input is 0?

A. OR gate B. AND gate C. NAND gate D. both (a) and (c)

Q30. Minimum number of interchange needed to convert the array 89, 19, 14, 40, 17, 12, 10, 2 , 5 ,7, 11, 6,

9,70, into a heap with the maximum element at the root is

A. 0 B. 1 C. 2 D. 3

------------------------ROUGH WORK-----------------------------------------------------------------------