BSNL previous years solved sample placement papers,BSNL DGM,JTO Tech Assistant questions with answers,BSNL model questions for practicce,BSNL technical assistant question papers wit answers and detalied explnations
1. Weins bridge is used for measurement of frequency in the applied voltage waveform is measurement of frequency in the applied voltage waveform is
(a) Sinusoidal (Ans)
(b) Square
(c) rectangular
(d) triangular
2. Strain gauge is
(a) not a transducer
(b) an active transducer (Ans)
(c) not an electronic
(d) none
3. A high Q coil has
(a) large band width
(b) high losses (Ans)
(c) low losses
(d) flat response
4. In the case of an instrument reading of 8.3V with a 0 to 150 voltmeter having a guaranteed accuracy of 1% full scale reading, the percentage limiting error is
(a) 1.810 %
(b) 0.181 %
(c) 12.45 % (Ans)
(d) 0.0018%
(Explanation : Limiting error at full scale = 1/100 X 150 = 1.5 volt
the true reading may be (8.3 + 1.5) Volt the relative error = 1.5/100 X 8.3 = 12.45 % )
5. The ‘h’ parameter equivalent circuit of a junction transistor is valid for
(a) High frequency, large signal operation
(b) High frequency, small signal operation
(c) Low frequency, small signal operation (Ans)
(d) Low frequency, large signal operation
6. A system is casual if the output of any time depends only on
(a) Values of input in the past and in the future
(b) Values of input at that time and in the past (Ans)
(c) Values of input at that time and in the future
(d) None
7. From the hot metal surface electrons escape because
(a) of change of state from metal to gas due to heat
(b) of change of state from gas to metal
(c) the energy greater than the work function (Ans)
(d) the energy is greater than Fermi level
8. The most common device used for detection in radio receivers is
(a) amplifier
(b) triode
(c) diode (Ans)
(d) transistor
9. In a full wave rectifier the negative point in a circuit is
(a) Cathode
(b) anode
(c) The central tap on the high voltage secondary (Ans)
(d) Plate
10. Negative feedback amplifier has a signal corrupted by noise as its input
(a) Amplify the noise as much as the signal
(b) Reduce the noise (Ans)
(c) Increase the noise
(d) Not effect the noise
PART II
11. It is an unidirectional device that blocks the current flow from cathode to anode
(a) SCR (Ans)
(b) PCR
(c) VCR
(d) DCR
12. An ideal constant current source is connected in series with an ideal constant voltage source. Considering together the combination will be a
(a) constant voltage source
(b) constant current source (Ans)
(c) constant voltage and a constant current source or a constant power source
(d) resistance
13. A node current in an thyristor is made up of
(a) electrons only
(b) electrons or holes
(c) electrons and holes (Ans)
(d) holes only
14. For a pulse transformer, the material used for its core and the possible turn ratio from primary to secondary are respectively
(a) ferrite : 20:1
(b) laminated iron : 1:1
(c) ferrite : 1:1 (Ans)
(d) powdered iron :1:1
15. A converter which can operate in both 3 pulse and 6 pulse modes is a
(a) 1 phase full converter
(b) 3 phase half wave converter
(c) 3 phase semi converter (Ans)
(d) 3 phase full converter
16. A single phase CSI has capacitor C as the load. For a constant source current, the voltage across the capacitor is
(a) square wave
(b) triangular wave (Ans)
(c) step function
(d) pulsed wave
17. A single phase full wave midpoint thyristor convertor uses a 230/200 V transformer with centre tap on the secondary side. The P.I.V per thyristor is
(a) 100 V
(b) 141.4V
(c) 200 V
(d) 282.8 V (Ans)
(Explanation : For centre taped transformer in output side the PIV = 2 Vrms = 2 x 200/√2 = 282.8 Volt)
18. In dc choppers for chopping period T, the output voltage can be controlled by FM by varying
(a) T keeping Ton constant (Ans)
(b) Ton keeping T constant
(c) Toff keeping T constant
(d) None of the above
19. An ideal power supply consist of
(a) A Very small output resistance
(b) Zero internal resistance (Ans)
(c) Very large input resistance
(d) Very large output resistance
20. The linearity error for a digital input is indicated by
(a) ξ
(b) y
(c) η
(d) ε (Ans)
21. In the 8421 BCD code the decimal number 125 is written as
(a) 1111101 (Ans)
(b) 0001 0010 0101
(c) 7D
(d) None of the above
Explanation :
22. Match the given feedback circuit with its proper nomenclatures
(a) Current series feedback (Ans)
(b) Current shunt feedback
(c) Voltage series feedback
(d) Voltage shunt feedback
23. Class A amplifier is used when
(a) No phase inversion is required
(b) Highest voltage gain is required
(c) dc voltages are to be amplified
(d) Minimum distortion is desired (Ans)
24. Identify the correct match for the give transistor
(a) Enhancement type P channel MOSFET
(b) Depletion type N channel MOSFET (Ans)
(c) Enhancement type N channel MOSFET
(d) Depletion type P channel MOSFET
25. In case a signal band limited to fermimeter is sampled at a rate less than 2 fermimeter , the constructed signal will be
(a) Distortionless
(b) Small in amplitude
(c) Having higher frequencies suppressed
(d) Distorted (Ans)
26. IC which has quad 2 input AND gates
(a) 7411
(b) 7404
(c) 7400
(d) 7408 (Ans)
27. Registers in which data is entered or taken out in serial form are referred as
(a) left shift register
(b) right shift register
(c) shift registers (Ans)
(d) none of the above
28. The expression ABC can be simplified to
(a) A B C
(b) AB + BC + CA
(c) A B + C
(d) A + B + C (Ans)
29. Read the following :
(i) Routh Herwitz’s criterion is in time domain
(ii) Root locus plot is in time domain
(iii) Bode plot is in frequency domain
(iv) Nyquist criterion is in frequency domain (Ans)
(a) 2, 3 and 4 are correct
(b) 1, 2 and 3 are correct
(c) 3 and 4 are correct
(d) All four are correct
30. Register and counters are similar in the sense that they both
(a) count pulses
(b) store binary operation
(c) shift registers
(d) made from an array of flip flops and gates integrated on a single chip (Ans)
31. In D/A converter, the resolution required is 50 mv and the total maximum input is 10 V. The number of bits required is
(a) 7
(b) 8 (Ans)
(c) 9
(d) 200
32. On differentiation unit impulse function results in
(a) Unit parabolic function
(b) Unit triplet
(c) Unit doublet (Ans)
(d) Unit ramp function
33. —— watt of power is received from sun per m2 surface area of a geosynchronous satellite
(a) 100
(b) 500
(c) 2000
(d) 1000 (Ans)
34. The ripple factor in an LC filter
(a) Increase with the load current
(b) Increases with the load resistance
(c) Remains constant with the load current
(d) Has the lowest value (Ans)
35. In different parts of the country identical telephone numbers are distinguished by their
(a) Language digits
(b) Access digits
(c) Area codes (Ans)
(d) Central office codes
36. Amplitude modulation is used for broadcasting because
(a) it is move noise immune than other modulation systems
(b) compared with other systems it requires less transmitting power
(c) its use avoids receiver complexity (Ans)
(d) no other modulation system can provide the necessary bandwidth for high fidelity
37. The maximum phase shift than can be provided by a lead compensator with transfer function
G0(S) = 1 + 6S
1 + 2S
(a) 15o
(b) 45o
(c) 30o (Ans)
(d) 60o
(Explanation : If GC(s) = 1 +Tn s
1 + Td s
then Q = tan -1 ωTn – tan-1 ωTd
Q = tan -1 6ω – tan-1 2ω
So maximum phase shift will be Q= 30o )
38. The correct sequence of steps required to improve system stability is
(a) Insert derivative action, use negative feedback, reduce again
(b) Reduce gain, use negative feedback, insert derivative action
(c) Reduce gain, insert derivative action, use negative feedback
(d) Use negative feedback, reduce gain, insert derivative action. (Ans)
39. Identify slope change at ω= 10 of the magnitude v/s frequency characteristic of a unity feedback system with the following open-loop transfer function
G (jω) = 5(1+j o.w)
jω (1 + j0.5ω) [ (1+j 0.6 ω/50) + ( jω/50)2]
(a) -80 dB/dec to – 60 dB/dec (Ans)
(b) 40 dB/dec to 20 dB/dec
(c) 20 dB/dec to – 40 dB/dec
(d) 40 dB/dec to – 20 dB/dec
(Explanation :
| Factor | Corner frequency | Gain and angle |
| 5 | —– | 20 log5=14dB line parallel to x axis |
| 1 jω |
—– | -20dB/dec passing through ω=1 |
| 1 1 + j0.5ω |
ω1=2 | -20dB/dec slope originates from ω=2 |
| 1+0 (1+j 0.6 ω/50) + ( jω/50)2 |
ω2=7.07 | -40 dB/dec slope originates from ω=7.07 |
| 1+j 0-1 ω | ω3=10 | +20dB/dec slope originates ω=10 |
40. In the feedback control system the loop transfer function is given by
G(s) H (s) = K
s(s+2) (s2 +2s +2)
Number of asymptotes of its root loci is
(a) 1
(b) 2
(c) 3
(d) 4 (Ans)
41. In a closed – loop transfer function
G (s) = 2600k(s + 25)
R (s) s4 +125s3 + 5100s2 + 65000s + 65000k
the imaginary axis intercepts of the root loci will be
(a) + j228 (Ans)
(b) +j2.28
(c) +j1.14
(d) +j114
42. Considering the following statement : In a magic tee
1. the collinear arms are isolated from each other
2. one of the collinear is isolated from the E-arm
3. one of the collinear arm is isolated from the H-arm
4. E-arm and H-arm are isolated from each other. of these statements
(a) 1 and 2 are correct
(b) 1 and 3 are correct
(c) 1 and 4 are correct (Ans)
(d) 2 and 3 are correct
43. In 1965 first geostationary satellite was launched called
(a) ANIK
(b) EARLY BIRD (Intel sat-1)
(c) WESTAR (Ans)
(d) MOLNIYA
44. When A = 0., B = 0, C=1 then in two input logic gate we get gate
(a) XOR gate
(b) AND gate
(c) NAND gate (Ans)
(d) NOR gate
45. In a radio receiver the IF amplifier
(a) is tuned above the stations incoming frequency
(b) amplifies the output of local oscillator
(c) is fixed tuned to one particular frequency (Ans)
(d) can be tuned to various isolate frequencies
46. A duplexer is used to
(a) couple two antennas to a transmitter without interference
(b) isolate the antennas from the local oscillator
(c) prevent interference between two antennas connected to a receiver (Ans)
(d) use an antenna for reception or transmission without interference
47. Boolean algebra is based on
(a) numbers
(b) logic (Ans)
(c) truth
(d) symbols
48. The amplifiers following the modulated stage in a low level modulation AM system be
(a) linear amplifier
(b) harmonic generators
(c) class C power amplifiers (Ans)
(d) class B untuned amplifiers
49. In a radar system maximum unambiguous range depends on
(a) maximum power of the transmitter
(b) pulse repetition frequency (Ans)
(c) width of the transmitted pulse
(d) sensitivity of the radar receiver
50. In composite video waveform the function of the serrations, is to
(a) equalize the charge in the integrator before the start of vertical retrace.
(b) help vertical synchronization
(c) help horizontal synchronization (Ans)
(d) simplify the generation of the vertical syncpulse.
51. The frequency range 30MHz – 300 MHz is
(a) medium frequency
(b) very high frequency (Ans)
(c) super high frequency
(d) infrared frequency
52. Which wave cannot exist inside wave guide
(a) TE
(b) TM
(c) TEM (Ans)
(d) HE
53. Ionosphere layer of earth is situated at
(a) upto 18kms from each
(b) from 18 to 70 k m
(c) 70 to 500 km (Ans)
(d) above 500 km
54. A two cavity klystron tube is a
(a) velocity modulated tube (Ans)
(b) frequency modulated tube
(c) Amplitude modulated tube
(d) simple triode
55. As the thermal noise get doubled due to the increase in a resistance the noise power get
(a) doubled
(b) quadrupted
(c) unchanged (Ans)
(d) halved
56. Which one is a cross field tube
(a) Klystron
(b) Reflex Klystron
(c) Magnetron (Ans)
(d) TWT
57. The degree of coupling depends on
(a) Size of hole
(b) location of holes (Ans)
(c) size and location of holes
(d) not depend on size or location of hole
58. The thermal noise depends on
(a) direct current through device
(b) resistive component of resistance (Ans)
(c) reactive component of impedance
(d) load to connected
59. The charge on a hole is
(a) 1.6 x 10-9
(b) 1.6 x 10-19 (Ans)
(c) 1.6 x 101
(d) 1.6 x 1020
60. Intel’s 8085 microprocessor chip contains
(a) seven 8 bit registers (Ans)
(b) 8 seven bits registers
(c) seven 7 bit registers
(d) eight 8 bit registers
PART -III
61. The words ‘Satyameva Jayate’ have been taken from
(a) Vedas (Ans)
(b) Bhagwad Gita
(c) Mahabharata
(d) None of these
62. Which of the following countries was the first to develop a neutron bomb?
(a) USA (Ans)
(b) USSR
(c) China
(d) Pakistan
63. ‘Kathakali’ dance is connected with
(a) Kerala (Ans)
(b) Rajasthan
(c) Uttar Pradesh
(d) Tamil Nadu
64. The term “Ashes” is associated with
(a) Hockey
(b) Cricket (Ans)
(c) Soccer
(d) None of these
65. The Kailash Temple at Ellora is a specimen of
(a) Gupta architecture
(b) Rashtrakutlas architecture
(c) Chalukya architecture
(d) Chola architecture (Ans)
66. When the two Houses of Parliament differ regarding a Bill then the controversy is solved by
(a) Joint sitting of the two Houses
(b) President of India
(c) Prime Minister of India (Ans)
(d) By a special committee for the purpose
67. Which of the following is not the work of Kalidasa ?
(a) Meghdoot
(b) Raghuvansha
(c) Sariputra Prakarma
(d) Ritushamhara (Ans)
68. Amir Khusro was the famous poet and aesthete of
(a) Akbar the Great (Ans)
(b) Mahmud Ghaznvi
(c) Shah Jahan
(d) Alauddin Khilji
69. With the beginnings of space travel, we entered a new
(a) Era of great history (Ans)
(b) List
(c) Book
(d) Year
70. An though it mourns the death of someone , need not be sad
(a) Funny poem
(b) Newspaper article
(c) Orthodox talk
(d) Elegy (Ans)
71. If stare is glance so gulp is
(a) Slip (Ans)
(b) Tell
(c) Salk
(d) Admire
72. He hardly works means
(a) The work is hard
(b) He is hard
(c) The work is easy
(d) He work very little (Ans)
73. Give the opposite word for pulchritude
(a) antipathy
(b) unsightliness (Ans)
(c) inexperience
(d) languor
74. Nanometre is —–part of a metre
(a) Millionth
(b) Ten millionth (Ans)
(c) Billionth
(d) Ten billionth
75. Malaria affects
(a) Liver
(b) Spleen (Ans)
(c) Intestine
(d) Lungs
76. Sindhu Rakshak is a/an
(a) Aircraft carrier
(b) Submarine
(c) Multiple-purpose fighter
(d) Anti-aircraft gun (Ans)
77. With which subject is “Dada Saheb Phalke Award” associated ?
(a) Best film director
(b) Best musician
(c) Best documentary (Ans)
(d) Best work relating to promotion of Indian film Industry
78. Who developed the branch of mathematics know as Calculus ?
(a) Aryabhatta
(b) Newton
(c) Einstein (Ans)
(d) Archimedes
79. In which state is Kanha Park situated ?
(a) M.P.
(b) U.P. (Ans)
(c) Assam
(d) W. Bengal
80. Which day is observed as Human Rights Day ?
(a) 24th October (Ans)
(b) 4th July
(c) 8th August
(d) 10th December