# RailTel Previous Year Question Paper - Comman

RailTel Previous Year Question Paper

1 The address resolution protocol (ARP) is used for
A) Finding the IP address from the DNS
B) Finding the IP address of the default gateway

2 Consider the following relation schema pertaining to a students database:
Enroll (rollno, courseno, coursename)
where the primary keys are shown underlined. The number of tuples in the Student and Enroll tables are 120 and 8 respectively. What are the maximum and minimum number of tuples that can be present in (Student * Enroll), where '*'denotes natural join?
A) 8, 8
B) 120, 8
C) 960, 8
D) 960, 120

3 Consider a direct mapped cache of size 32 KB with block size 32 bytes. The CPU generates 32 bit addresses. The number of bits needed for cache indexing and the number of tag bits are respectively
A) 10, 17
B) 10, 22
C) 15, 17
D) 5, 17

4 The goal of structured programming is to
A) have well indented programs
B) be able to infer the flow of control from the compiled code
C) be able to infer the flow of control from the program text
D) avoid the use of GOTO statements

5 The tightest lower bound on the number of comparisons, in the worst ease, for comparison-based sorting is of the order of
A) n
B) n 2
C) n log n
D) n log2 n

6 Let G be a simple graph with 20 vertices and 100 edges. The size of the minimum vertex cover of G is 8. Then, the size of the maximum independent set of G is
A) 12
B) 8
C) Less than 8
D) More than 12

7 WA and B are the only two stations on an Ethernet. Each has a steady queue of frames to send. Both A and B attempt to transmit a frame, collide, and A wins the first backoff race. At the end of this successful transmission by A, both A and B attempt to transmit and collide. The probability that A wins the second backoff race is
A) 0.5
B) 0.625
C) 0.75
D) 1.0

8 Let A be a sequence of 8 distinct integers sorted in ascending order. How many distinct pairs of sequences, B and C are there such that (i) each is sorted in ascending order, (ii) B has 5 and C has 3 elements, and (iii) the result of merging B and C gives A?
A) 2
B) 30
C) 56
D) 256

9 In a network of LANs connected by bridges, packets are sent from one LAN to another through intermediate bridges. Since more than one path may exist between two LANs, packets may have to be routed through multiple bridges.Why is the spanning tree algorithm used for bridge-routing?
A) For shortest path routing between LANs
B) For avoiding loops in the routing paths
C) For fault tolerance
D) For minimizing collisions

10 A Priority-Queue is implemented as a Max-Heap. Initially, it has 5 elements. The level-order traversal of the heap is given below: 10, 8,5,3,2 Two new elements 1 and 7 are inserted in the heap in that order. The level-order traversal of the heap after the insertion of the elements is
A) 10,8,7,5,3,2,1
B) 10,8,7,2,3,1,5
C) 10,8,7,1,2,3,5
D) 10,8,7,3,2,1,5

11 An organization has a class B network and wishes to form subnets for 64 departments. The subnet mask would be
A) 255.255.0.0
B) 255.255.64.0
C) 255.255.128.0
D) 255.255.252.0

12 Suppose the round trip propagation delay for a 10 Mbps Ethernet having 48-bit jamming signal is 46.4 ms. The minimum frame size is:
A) 94
B) 416
C) 464
D) 512

1 3The order of an internal node in a B+ tree index is the maximum number of children it can have. Suppose that a child pointer takes 6 bytes, the search field value takes 14 bytes, and the block size is 512 bytes. What is the order of the internal node?
A) 24
B) 25
C) 26
D) 27

14 The Boolean function x, y, + xy + x, y
A) x, + y,
B) x + y
C) x + y,
D) x, + y

15 In an MxN matrix such that all non-zero entries are covered in a rows and b columns. Then the maximum number of non-zero entries, such that no two are on the same row or column, is
A) � a + b
B) � max {a, b}
C) � min {M-a, N-b}
D) � min {a, b}

16 The relation scheme Student Performance (name, courseNo, rollNo, grade) has the following functional dependencies:
C) name -> rollNo
D) rollNo -> name
The highest normal form of this relation scheme is

17The minimum number of page frames that must be allocated to a running process in a virtual memory environment is determined by
the instruction set architecture
B) page size
C) physical memory size
D) number of processes in memory

18Let G be a simple graph with 20 vertices and 100 edges. The size of the minimum vertex cover of G is 8. Then, the size of the maximum independent set of G is
A) 12
B) 8
C) Less than 8
D) More than 12

19What does the following algorithm approximate? (Assume m > 1, � > 0).
x = m;
y-i;
while (x - y > �)
{ x = (x + y) / 2 ;
y = m/x ;
}
print (x) ;

A) log m
B) m2
C) m1/2
D) m1/3

20 Consider the following C program

main ()
{ int x, y, m, n ;
scanf ("%d %d", &x, &y);
/ * Assume x > 0 and y > 0 * /
m = x; n = y ;
while ( m ! = n)
{ if (m > n)
m = m � n;
else
n = n - m ; }
printf("%d",n); }

The program computes
A) x + y, using repeated subtraction
B) x mod y using repeated subtraction
C) the greatest common divisor of x and y
D) the least common multiple of x and y

21The best data structure to check whether an arithmetic expression has balanced parentheses is a
A) queue
B) stack
C) tree
D) list

22A Priority-Queue is implemented as a Max-Heap. Initially, it has 5 elements. The level-order traversal of the heap is given below: 10, 8,5,3,2 Two new elements 1 and 7 are inserted in the heap in that order. The level-order traversal of the heap after the insertion of the elements is
A) 10,8,7,5,3,2,1
B) 10,8,7,2,3,1,5
C) 10,8,7,1,2,3,5
D) 10,8,7,3,2,1,5

23 An organization has a class B network and wishes to form subnets for 64 departments. The subnet mask would be
A) 255.255.0.0
B) 255.255.64.0
C) 255.255.128.0
D) 255.255.252.0

24 Suppose the round trip propagation delay for a 10 Mbps Ethernet having 48-bit jamming signal is 46.4 ms. The minimum frame size is:
A) 94
B) 416
C) 464
D) 512

25The following numbers are inserted into an empty binary search tree in the given order: 10, 1, 3, 5, 15, 12, 16. What is the height of the binary search tree (the height is the maximum distance of a leaf node from the root)?
A) 2
B) 3
C) 4
D) 6

26 Consider the following C function:
int f (int n)
{ static int i = 1;
if (n >= 5) return n;
n = n + i;
i ++;
return f (n);
}
27The value returned by f(1) is
A) 5
B) 6
C) 7
D) 8

28 The minimum number of page frames that must be allocated to a running process in a virtual memory environment is determined by
A) the instruction set architecture
B) page size
C) physical memory size
D) number of processes in memory

1. Dimensions of Power:
a) M1L2T-3,
b) M1L2T-2,
c) M1L1T-3

2. Torque in Induction Motor is directly proportional to:
a) V,
b) V(pwr)
c) V(pwr)
d) V(pwr)1/2

3. Power in Transmission lines is proportional to:
a) V,
b) V(pwr)2,
c) V(pwr)
d)V(pwr)1/2

4. Flashover at the surface of condenser bushings is due to:

5. When Surge impedance equal characteristic impedance then :
a) Vs = Vr,
b) Vs> Vr,
c) Vs< Vr,

6. Stability limit is higher in:
b) Transient state,
c) Sub transient state,

7. Those instruments which give constants and direction only are called:
a) Secondary type,
b) Absolute type,
c) Deflection type,
d) Integrating type.

8. The internal resistance of a meter is 4 ohm and current drawn is 30mA. If we want to increase its range as voltmeter upto 150V then find out the series resistance added in the circuit?
Ans. 4996 ohm

9.If relay setting is at 125% and the CT ratio is 400/5, then the fault current in hv winding is?
Ans. 6.25 amp.

10. If capacitve reactance of a 200 km line is 2000 ohm then what will be the charging reactance of a 100 km line?
a) 2000
b) 4000ohm,
c) 500 ohm,
d) 8000ohm.

11. Which is wrong:
a) Transient response is frequency domain.
b) Routh criteria is stability based.
c) Nyquist is time domain.

12. With the increase in feedback of the system which will increase:

13. Mechanical stress is max. at which part of the cable:

14. Underground cable laying is done by:
ans. conduits and piping.

15. Operation and maintenance cost is min. in which of the following plants:
a) Thermal,
b) Nuclear,
c) Hydel,
d) Diesel.

16. Earliest power plant is:
a) Thermal,
b) Nuclear,
c) Unconventional,

17. Circuit Breaker arcing contacts are made of which material:
a) copper tungsten
b) copper,
c) silver,
d) graphite.

18. The reflection coefficient for voltage of a short circuited line is:
a) -1, b) 1, c) 0, d) 2

19. Double cage rotor is used in Induction motor is to improve:
Ans. starting torque.

20. If resistance of the secondary winding of the transformer is given as .02ohm and reactance .06ohm then find out the primary resistance and reactance respectively:
Ans. .08 ohm and .24ohm

21. Skewing in the squirrel cage rotor of Induction motor is purposely done to :
Ans. to avoid interlocking and reduce noise.

22. Capacitance of 3phase line is given 4microF. if we consider single line to ground then its capacitance will be:
a) 4microF,
b) 2microF,
c) 1microF,
d) 8microF

23. The normal frequency RMS voltage that appears across the breaker poles after final arc extinction is known as:
Ans. Recovery voltage

24. In power factor meter , which element is used as shunt in instruments:
a) silver,
b) copper,
c) manganin

25. .If anode of the SCR is made positive and cathode is made negative thenit will be:
Ans. forward biased and conducting.

26. Natural commutation is done in...
a) cycloconverters,
b) choppers,
c) AC voltage controllers,

27.Class B insulation is done in :

28. The highest range of temperature of insulations is...
Ans. 180

29. Temperature of the boiler furnace is measured by:
Ans. optical pyrometer

30. Resistivity of insulators with temperature
a) decreases linearly,
b) decreases exponentially,
c) increases,
d) remains same.

31. On increasing the frequency of the transformer , hysterisis loss and eddy current loss respectively:
a) decreases and remains same,
b) decreases and increases,
c) both increases ,
d) both decreases.

32. Rotor copper losses are small in Induction Motor as compared to transformer becoz:
Ans. Rotor core is laminated.

33. Arrange the following in ascending order: resistance split, capacitor start capacitor run etc motors were given...

34. Which type of turbine is used in tydel power generation:
a) Kaplan, b) Fransis, c) Pelton Wheel type, d) Reverse type.

35. Which of the following is the distribution 3 phase voltage:
a) 220 V, b) 415 V, c) 680 V, d) 800 V.

36. Which of the following bridges is used to measure dielectric losses in capacitor:
a) Schearing Bridge,
b) Wein's Bridge,
c) De-Sauty Bridge,
d) Maxwell Bridge.

37. Cros have which of the following...

38. A full wave centre tap thyristor is given.. find out the PIV..? dnt remember exactly some values were given...
a) 141.3 V, b) 100 V, c) 248.2 V, etc..
.
39. Speed of the Induction Motor at full load is 1400 rpm , what will be the speed at half the load...
a)1400rpm, b) 1420rpm, c) 1440rpm, d) 1460rpm.

40. The line feeding from distribution system to the consumers is called:
a) feeder, b) service mains, c) distributor, etc...

41. Which of the following generation plant is most reliable.
ans. Interconnected system.

42. Lload current in thyristor depends upon.....
a) delay angle and load type,
b) delay angle but not on load type,
c) only delay angle,

43. Buchholz relay is:
a) a gas actuated relay,
b) current sensitive relay,
c) overcurrent relay,
d) over voltage relay.

44. Diac is a:
a) 4 terminal 2junction device,
b) 3 terminal 2 junction device,
c) 5 terminal 3 junction device,
d) 6 terminal 3 junction device.

45. Dual converter consists of:
Ans. 1 converter and 1 inverter.

46. Slip is min. for which of the following machine:
a) 25HP,4 Pole ,
b) 1HP, 4 pole,
c) 2 HP , 6 pole,
) 25 HP, 6 Pole.

47. In Air Blast circuit breakers the air pressure inside is:
a) 1kg/cm2,
b) 100 mm of Hg ,
c) 20-30 kg/cm2,
d) 200-300 kg/cm2.

48. 1Barrel contains how much litres:

49. DC Choppers are used to convert:
a) DC to DC,
b) AC to DC,
c) AC to AC,

50.. How the corona effect varies with size and frequency, it increases with..
a) increasing size and reducing supply frequency, b) reducing size and incresing supply frequency, etc...

51. 1 ques was based on..... in frequency variable method which of the following factor is kept constant:
a) V/f = constant,
b) Vf = constant,
c)V=constant,
d) none of these..

52. 1 ques was based on ..... relation of Voltage with load angle delta..... options were...
a) V/1-& ,
b) V/1+&,
c) 1-&/&V,
d) &/(1-&)V

53.Universal motor is:
a) frequency dependent,
b) frequency independent,

54. If CT winding connections are made in star/delta on the primary side of the T/F then CT connections on the secondary side winding of T/F will be:
Ans. delta/star.

55. slip rings in DC machines are made of:
a) carbon,
b) graphite,
c) copper alloy,
d) copper.

56Bbending radius of the cable should be:
a) D, b)2D, c) 3D, d) 4D

57. 1 ques like..... In cycloconverters the O/P frequency power factor will bw as compared to I/P frequency power factor:
a) higher, b) lower, c) same..

58. In higher rating transformers the tank is of the following type:
a) radiator, b) oil tank, c) seperator,

59. Merz Price protection is used in :
a) Alternator, b) Transmission lines, c) Transformer,

60. Meggar is:
a) moving coil type,
b) moving iron type,

61. Differential relay is:
a) over current relay,
b) over voltage relay,

62. Two transformers are connected in parallel R/X is smthing..... then the currents in the two T/F will be:
a) Ia lags Ib ,
c) both will be in phase,

63. skin effect does not depend upon:
Ans. ambient temperature.

64. . AC resistance is more due to....
Ans. skin effect

65. Human body gets shock due to:
a) static charge discharging of body,
b) voltage induced in the body,
c) current induced in thebody,
d)none of these
.
66. Heavy water in nuclear reactor is used as:
a) accelerating agent,
b) decclerating agent,
c) lubricating agent,
d) cooling agent.

67. specifications of earth plate are:
a) 60* 60*12.5 , b) 90*90*12.5

68. Distance of ground electrode from building is:
a) 1m, b) 2m, c) 3m , d)4m

69. Why earth pit is filled with alternate layers of salt and charcoal:
Ans. to reduce earth's resistance.

70. If cos& is a power factor, then MVAR ia proportional to:

71.why central phase is reversed.....(smthing dnt remember exactly)

72. capacitors are connected where at the transmission line:
a) at sending end,
b) at receiving end,
c) in the middle of the line,

73. Which gas is used in the gas fired prime movers at gas power plants: