Lucknow Metro Rail Corporation Ltd. Junior Engineering Examination Held on 17-3-2016 Electronics and Telecommunications Question Paper With Answer Key

Lucknow Metro Rail Corporation Ltd. Junior Engineering Examination Held on 17-3-2016

1. A NAND gate has-

(A)  LOW Inputs and a HIGH output

(B)  LOW inputs and LOW output

(C)  HIGH inputs and a HIGH output

(D)  HIGH inputs and LOW outputs

Answer: (A)

2. When the time period of observations is large the type of the error is-

(A)  Position error constant

(B)  Steady state error

(C)  Transient error

(D)  Half power error

Answer: (B)

3. Magnetrostriction is a phenomenon where the magnetization of a ferromagnetic material leads to a change in-

(A)  magnetic susceptibility

(B)  physical dimensions

(C)  spontaneous magnetization

(D)  relative permeability

Answer: (D)

4. When an electron jumps from the valence shell to the conduction band it leaves a gap. What is the gap called?

(A)  electron hole pair

(B)  recombination

(C)  hole

(D)  energy gap

Answer: (D)

5. An inductor stores energy in-

(A)  electrostatic field

(B)  electromagnetic field

(C)  core

(D)  magnetic field

Answer: (D)

6. The characteristics equation s3 – 3s2 – 3s – k = 0 stable for which value of k?

(A)  1

(B)  0

(C)  5

(D)  −6

Answer: (B)

7. The accuracy of a meter is determined by ………….. deflection.

(A)  Full-scale

(B)  Half-scale

(C)  One-fourth of full scale

(D)  One-tenth of full scale

Answer: (A)

8. Dead zone of an instrument is-

(A)  the largest change of input quantity for which there is no output of the instrument

(B)  the time required by an instrument system to begin to respond to a change in measurement

(C)  the unmeasured quantity which is more than the maximum range of the instrument

(D)  change in measuring time

Answer: (C)

9. (−1/2 – j0) is the centre of a constant N-circle is G-plane. Phase-angle will be-

(A)  45°

(B)  180°

(C)  0°

(D)  90°

Answer: (C)

10. A device that converts from decimal to binary numbered is called-

(A)  encoder

(B)  decoder

(C)  CPU

(D)  converter

Answer: (A)

11. The magnetic susceptibility of a paramagnetic material is-

(A)  less than one  but positive

(B)  greater than one

(C)  equal to zero

(D)  less than zero

Answer: (B)

12. A circuit in which the output is the ramp pulses for an input of square pulses then-

(A)  It is an integrating circuit with low RC

(B)  It is a differentiating circuit with high RC

(C)  It is a differentiating circuit with low RC

(D)  It is an integrating circuit with high RC

Answer: (B)

13. Convert the binary number 1001.0010 to decimal-

(A)  9.125

(B)  125

(C)  90.125

(D)  12.5

Answer: (A)

14. The following circuit gives the output-

(A)  ABCDE

(B)  [{C(A + B)D}E’]

(C)  C(A + B)DE

(D)  [C(A + B)D + E’]

Answer: (C)

15. ……….. cannot be used to measure pressure.

(A)  Strain gauge

(B)  Pyrometer

(C)  LVDT

(D)  Pirani gauge

Answer: (B)

16. In case of synchro error detector, the electrical zero position of control-transformer is obtained when angular displacement between rotors is-

(A)  45°

(B)  180°

(C)  90°

(D)  Zero system

Answer: (B)

17. Convert the binary number 1011010 to hexadecimal-

(A)  5F

(B)  5C

(C)  5A

(D)  5B

Answer: (C)

18. The super-position theorem is applicable to-

(A)  both current and voltage

(B)  current only

(C)  voltage only

(D)  current, voltage and power

Answer: (D)

19. What causes the depletion region ?

(A)  diffusion

(B)  barrier potential

(C)  ions

(D)  doping

Answer: (A)

20. Exclusive-OR (XOR) logic gates can be constructed from what other logic gates?

(A)  AND gates, OR gates, NOT gates

(B)  OR gates and NOT gates

(C)  OR gates only

(D)  AND gates and NOT gates

Answer: (A)

21. Figure below represent a-

(A)  Power diode

(B)  Triac thyristor

(C)  Capacitive diode

(D)  Diac trigger

Answer: (B)

22. What will be the state of a silicon diode if the voltage drop across it is about 0.7 V?

(A)  Forward bias

(B)  Zener region

(C)  Reverse bias

(D)  No bias

Answer: (*)

23. How many orbiting electron does the germanium atom have?

(A)  4

(B)  41

(C)  14

(D)  32

Answer: (A)

24. What is the resistor value of an ideal diode in the region of conduction?

(A)  infinity

(B)  undefined

(C)  0Ω

(D)  5 kΩ

Answer: (C)

25. If an induction type energy meter runs fast, it can be slowed down by-

(A)  adjusting the position of braking magnet and making it come closer to the centre of the disc

(B)  lag adjustment

(C)  light load adjustment

(D)  adjusting the position of braking magnet and making it move away from the centre of the disc

Answer: (D)

26. The maximum value of a controller output is 100 V and is obtained when the input error is IV. If the controller is working at 20% proportional band, the error and output will be respectively?

(A)  1 V and 20 V

(B)  0.2 V and 120 V

(C)  1 V and 120 V

(D)  0.2 V and 100 V

Answer: (D)

27. If there are b branches and n nodes, the number of equations will be-

(A)  n-1

(B)  b-n

(C)  b

(D)  b-n-1

Answer: (D)

28. Liquid crystal material is used in-

(A)  Ultrasonic amplification and display devices

(B)  Display devices and thermal sensors

(C)  Thermal sensors and transducers

(D)  Transducers and ultrasonic amplification

Answer: (B)

29. Root loci stars from-

(A)  poles and ends on zero

(B)  poles and ends on infinity

(C)  zeros and ends on pole

(D)  zeros and ends on infinity

Answer: (D)

30. For a design of the binary counter preferred types of flip-flop is-

(A)  SR type

(B)  JK type

(C)  Latch

(D)  D-type

Answer: (B)

31. In P type semiconductor material, minority carriers would be-

(A)  slower

(B)  holes

(C)  dopants

(D)  electrons

Answer: (D)

32. What unit is used to represent the level of diode forward current IF?

(A)  mA

(B)  μA

(C)  pA

(D)  p/A

Answer: (A)

33. The radio-communication spectrum is divided into bends based on-

(A)  Amplitude

(B)  Cost and hardware

(C)  Frequency

(D)  Transmission media

Answer: (C)

34. Which material may also be considered a semiconductor element?

(A)  carbon

(B)  argon

(C)  ceramic

(D)  mica

Answer: (A)

35. Forward bias of a silicon P-N junction will produce a barrier voltage of approximately how many volts?

(A)  0.7

(B)  0.8

(C)  0.3

(D)  0.2

Answer: (A)

36. An accurate ammeter must have a resistance of-

(A)  high value

(B)  very high value

(C)  low value

(D)  very low value

Answer: (D)

37. Calculate the power dissipation of a diode having Id = 40 mA-

(A)  28 mW

(B)  28 W

(C)  undefined

(D)  280 mW

Answer: (A)

38. An ohmmeter is a-

(A)  Moving iron instrument

(B)  Moving coil instrument

(C)  Dynamometer instrument

(D)  Moving iron and moving coil both

Answer: (D)

39. Which capacitance dominates in the forward-bias region?

(A)  Transition

(B)  Diffusion

(C)  Depletion

(D)  Drift

Answer: (B)

40. A positive AND gate is also a negative-

(A)  NAND gate

(B)  AND gate

(C)  NOR gate

(D)  OR gate

Answer: (D)

41. The main difference between the electronic and electrical instruments is that an electronic instrument has-

(A)  a digital readout

(B)  transducer

(C)  an electron device

(D)  an indicating device

Answer: (A)

42. The transducers in a measurement system is the-

(A)  signal-conditioning device

(B)  output element

(C)  input element

(D)  processing device

Answer: (A)

43. Ultrasonic amplification through electron-photon interaction is generally achieved using a-

(A)  Superconductor

(B)  Piezoelectric material

(C)  Paramagnetic material

(D)  Elemental semiconductor

Answer: (A)

44. 8085 has ……….. software restarts and …………. hardware restarts.

(A)  6, 6

(B)  10, 5

(C)  7, 5

(D)  8, 4

Answer: (D)

45. Convert the decimal number 151.75 to binary-

(A)  11010011.01

(B)  10010111.11

(C)  00111100.00

(D)  10000111.11

Answer: (B)

46. In a cable capacitor, voltage gradient is maximum at the surface of the-

(A)  Conductor

(B)  Sheath

(C)  Dielectric

(D)  Earth

Answer: (A)

47. The temperature coefficient of resistance of an insulator is-

(A)  Negative and independent to temperature

(B)  Negative and dependent on temperature

(C)  Positive and dependent on temperature

(D)  Positive and independent of temperature

Answer: (B)

48. Piezoelectric materials owe their property to the-

(A)  Lack of axis of symmetry

(B)  Presence of a centre of a symmetry

(C)  Lack of a centre of symmetry

(D)  Presence of axis of summetry

Answer: (D)

49. In a CRO, the time base signal is a-

(A)  High frequency sinusoidal waveform

(B)  Square waveform

(C)  High frequency saw tooth waveform

(D)  Rectangular waveform

Answer: (C)

50. In case of delta connected circuit, when one resistor is open, power will be-

(A)  unaltered

(B)  reduced to 1/3

(C)  reduced by 1/3

(D)  zero

Answer: (A)

51. The output will be a LOW for any case when one or more inputs are zero is a-

(A)  NOT gate

(B)  NAND gate

(C)  OR gate

(D)  AND gate

Answer: (D)

52. Highest operating frequency can be expected in the case of-

(A)  JFET

(B)  All the other given option have nearly same frequency

(C)  MOSFET

(D)  Bipolar transistor

Answer: (D)

53. Which one of the following compensation is adopted for improving transient response of a negative unity feedback system?

(A)  gain compensation

(B)  both phase lag compensation and gain compensation

(C)  phase lag compensation

(D)  phase lead compensation

Answer: (B)

54. The resistances 15.3 Ω, 7 Ω, 13 Ω and 4.7 Ω are connected series. The equivalent resistance will be-

(A)  40 Ω

(B)  25 Ω

(C)  0.025 Ω

(D)  0.04 Ω

Answer: (A)

55. Which of the examples below expresses the commutative law of multiplication?

(A)  A ∙ B = B ∙ A

(B)  A + B = B + A

(C)  A ∙ (B ∙ C) = (A ∙ B) ∙ C

(D)  A ∙ B = B + A

Answer: (C)

56. An ammeter is a-

(A)  recording instrument

(B)  integrating instrument

(C)  absolute instrument

(D)  secondary instrument

Answer: (C)

57. A unit impulse function on differentiation results in-

(A)  unit triplet

(B)  unit doublet

(C)  unit parabolic function

(D)  unit ramp function

Answer: (D)

58. Elements with 1, 2 or 3 valence electrons usually make excellent-

(A)  neutral

(B)  conductor

(C)  semiconductor

(D)  insulator

Answer: (B)

59. The Major cause of creeping in an energy meter is-

(A)  over-compensation for friction

(B)  excessive voltage across the potential coil

(C)  mechanical vibrations

(D)  stray magnetic fields

Answer: (D)

60. The term zero effect is associated with-

(A)  quality control

(B)  radars

(C)  transistors

(D)  transmission lines

Answer: (A)

61. Standard TTL has a multiple emitter input transistor and a …………. output.

(A)  Register

(B)  Totem-pole

(C)  Bipolar

(D)  Transistor

Answer: (B)

62. Regarding VTVM which of the following statements is incorrect?

(A)  It is usually plugged into power supply line

(B)  It measures AC volts

(C)  Its ohm rangers are usually up to RX 1000 Ω

(D)  It cannot measure directly

Answer: (D)

63. Which one of following is a disadvantage of proportional controller?

(A)  It has very simple implementation

(B)  It produces offset

(C)  It makes responses faster

(D)  It destabilizes the system

Answer: (D)

64. In N-type material majority carriers would be-

(A)  dopants

(B)  electrons

(C)  holes

(D)  slower

Answer: (B)

65. What is the result when a decimal 5238 is converted to base 16 ?

(A)  327.375

(B)  12166

(C)  1476

(D)  1388

Answer: (C)

66. The observation that a bubbled input OR gate interchangeable with a bubbled output AND gate is referred to as-

(A)  the commutative law of addition

(B)  de-morgan’s second theorem

(C)  a karnaugh map

(D)  the associative law of multiplication

Answer: (B)

67. Ionization within a P-N junction causes a layer on each side of the barrier called the-

(A)  forward voltage

(B)  junction

(C)  depletion region

(D)  barrier voltage

Answer: (C)

68. The coercive force in ferromagnetic material is related to the-

(A)  Intercept on the negative H-axis of the B-H loop

(B)  Area enclosed by the B-H loop

(C)  Maximum value of B on the B-H loop

(D)  Intercept on the positive B-axis of the B-H  loop

Answer: (B)

69. An electronic instrument essentially consists of-

(A)  a transducer

(B)  an indicating device

(C)  a digital readout

(D)  an electron device

Answer: (C)

70. When is a P-N junction formed?

(A)  Whenever there is a forward voltage drop

(B)  The point at which two opposite doped materials come together

(C)  In a large reverse biased region

(D)  In a depletion region

Answer: (B)

71. What is an energy gap ?

(A)  The energy equal to the energy acquired by an electron passing a IV electric field

(B)  Energy difference between conduction band and valence band

(C)  An energy level at which an electron can exist

(D)  The space between two orbital shell

Answer: (B)

72. A potentiometer may be used for-

(A)  Measurement of energy

(B)  Measurement of resistance

(C)  Calibration of ammeter and voltmeter

(D)  Measurement of current

Answer: (C)

73. The relaxation time (τ) in a perfect dielectric is-

(A)  0

(B)  1 < τ < ∞

(C)  1

(D)  ∞

Answer: (B)

74. As compared to oscillators an inverter provides-

(A)  low voltage output

(B)  low frequency output

(C)  noiseless output

(D)  distortionless output

Answer: (D)

75. The multiplier and the meter coil in a voltmeter are connected in-

(A)  No connection

(B)  Mixed

(C)  Series

(D)  Parallel

Answer: (D)

76. The ceramic dielectrics used in electrical engineering include-

(A)  Cermet and Silicide

(B)  Porcelain and Cermet

(C)  Cordierite and Porcelain

(D)  Silicide and Cordierite

Answer: (C)

77. A coil having a inductance of 75 H is carrying a current of 100 A. If the current is reduced to zero in 0.2 second, the self-inductance e.m.f. will be-

(A)  375 V

(B)  500 V

(C)  125 V

(D)  750 V

Answer: (A)

78. What is the decimal value of the hexadecimal number 777?

(A)  1911

(B)  19

(C)  191

(D)  19111

Answer: (A)

79. How many truth table entries are necessary for a four-input circuit?

(A)  16

(B)  12

(C)  4

(D)  8

Answer: (A)

80. Which semi-conductor device acts like a diode and two resistors ?

(A)  SCR

(B)  Diac

(C)  Triac

(D)  UJT

Answer: (D)

81. Intrinsic semiconductor material is characterized by a valence shell of how many electrons?

(A)  1

(B)  6

(C)  2

(D)  4

Answer: (D)

82. How many 3 to 8 line decoder are required for a 1 of 32 decoder?

(A)  4

(B)  8

(C)  2

(D)  1

Answer: (A)

83. A P-N junction depicts a closed switch when it-

(A)  cannot overcome its barrier potential

(B)  is reversed biased

(C)  has a low junction resistance

(D)  has a wide depletion region

Answer: (C)

84. The room temperature resistivity (in ohm-meter) of pure silicon is-

(A)  3

(B)  3000

(C)  300

(D)  30

Answer: (C)

85. The effect of adding poles and zero can be determined quickly by-

(A)  Nicholas chart

(B)  Bode plot

(C)  Root locus

(D)  Nyquist plot

Answer: (B)

86. What type of magnetic behaviour is observed in a type I super-conductor?

(A)  perfect diamagnetism

(B)  perfect ferrimagnetism

(C)  perfect ferromanetism

(D)  perfect  paramagnetism

Answer: (C)

87. If the instrument is to have a wide range, it should have-

(A)  square-law scale

(B)  linear scale

(C)  logarithmic scale

(D)  exponential scale

Answer: (B)

88. The diffused impurities with how many valence electrons are called donor atoms?

(A)  4

(B)  3

(C)  0

(D)  5

Answer: (D)

89. The period of a periodic wave is-

(A)  expressed in volts

(B)  the same as the frequency

(C)  the time required to complete one cycle

(D)  measured in wavelengths

Answer: (C)

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