BSNL EXAMS MCQ’s ( Electronics & Communication )

1. Power diode is generally made from

Silicon

Germanium

Both

None of these

2. When the both junction of NPN diode is reverse biased, then the diode is in which mode

Active

Cutoff

Saturation

inverted

3. Which transistor mode gives the inverted output

Common Emitter

Common Base

Common Collector

None of these

4. Which coupling gives the higher gain in case of amplifier

Capacitor coupling

Impedance coupling

Transformer coupling

None of these

5. Which distortion is least objectionable in audio amplification

Phase

Frequency

Harmonic

Inter mediation

6. A narrow band amplifier has a band pass nearly…………of central frequency

33.3%

10%

50%

25%

7. Phase shift oscillator consists

RL

RC

RLC

LC

8. Multivibrater Produces

Sine wave

Square wave

Smooth wave

sawtooth

9. Convert the 101101 Binary number into octal no

65

55

51

45

10. The number10 is represented in BCD Number System

10100

1100

010111

None of these

11. Which PNP device has a terminal for synchronizing purpose

SCS

Triac

Diac

SUS

12. Addition of indium in semiconductor crystal makes

PNP

NPN

PNPN

NPNP

13. Free electron exists in which band

1

2

3

Conduction band

14. Ripple factor of half wave rectifier

1.21

0.48

0.5

None of these

15. Transistor that can be used in enhancement mode

NPN

UJT

JFET

MOSFET

16. Following contributes to harmonic distortion in Amplifier

+Ve feedback

–Ve feedback

Defective active device

None of these

17. High cutoff frequency

CB

CC

CE

None of these

18. Which is used as data selector?

Encoder

Decoder

modulator

Demodulator

19. Read write capable memory

RAM

ROM

Both

None of these

20. the radix or base of hexadecimal number system is -----------

8

16

5

none of these

21. the no of 1’s in the binary representation of the expression 162*9+162*7+16*5+3 are

10

23

6

4

22. the no of latches in F/F are -------

1

2

3

4

23. how many flip-flops are required to construct Mod -12 counter

5

4

12

none

24. which logic gate has the output is compliment of its input ----------

OR

AND

NOT

X-OR

25. no.of 2-input multiplexers needed to construct a 210 input multiplexer…….

12

31

20

16

26. Any number with an exponent of zero is equal to:

zero

one

that number

ten

27. In the decimal numbering system, what is the MSD?

The middle digit of a stream of numbers

The digit to the right of the decimal point

The last digit on the right

The digit with the most weight

28. Which of the following statements does NOT describe an advantage of digital technology?

The values may vary over a continuous range.

The circuits are less affected by noise.

The operation can be programmed.

Information storage is easy.

29. The generic array logic (GAL) device is ________.

one-time programmable

reprogrammable

a CMOS device

reprogrammable and a CMOS device

30. The range of voltages between VL(max) and VH(min) are ________.

unknown

unnecessary

unacceptable

between 2 V and 5 V

31. What is a digital-to-analog converter?

It takes the digital information from an audio CD and converts it to a usable form.

It allows the use of cheaper analog techniques, which are always simpler.

It stores digital data on a hard drive.

It converts direct current to alternating current.

32. What are the symbols used to represent digits in the binary number system

0,1

0,1,2

0 through 8

1,2

33. A full subtracter circuit requires ________.

two inputs and two outputs

two inputs and three outputs

three inputs and one output

three inputs and two outputs

34. The output of an AND gate is LOW ________.

all the time

when any input is LOW

when any input is HIGH

when all inputs are HIGH

35. Give the decimal value of binary 10010.

6

9

18

20

36. A mathematical operation for finding the area under the curve of a graph is called

__________.

differentiation

integration

curve averaging

linear regression

37. .An astable multivibrator is also known as a:

one-shot multivibrator

free-running multivibrator

bistable multivibrator

monostable multivibrator

38. A sample-and-hold circuit consists of _________.

An op-amp, an analog switch, and an inductor

An op-amp, an analog switch, and a capacitor

two op-amps, an analog switch, and a variable resistor

two op-amps, an analog switch, and a capacitor

39. An example of potential energy is:

tea-kettle steam

a moving vehicle

the sun

a battery

40. What is the applied voltage for a series RLC circuit when IT = 3 mA, VL = 30 V, VC = 18 V, and

R = 1000 ohms?

3.00 V

12.37 V

34.98 V

48.00 V

41. The number of digits in octal system is?

8

7

8 or 7

10

42. The number of digits in hexadecimal system is?

15

10

16

8

43. The number of bits in a nibble is?

8

2

4

16

44. The digit F in hexadecimal system is equivalent to number...........in decimal system?

16

15

17

8

45. Which of the following binary number is equivalent to decimal 10?

1010

1000

1001

1100

46. The number FF in a hexadecimal system is equivalent to number..........in a decimal system ?

256

240

255

239

47. ICs are?

analog

digital

both Analog and digital

mostly analog

48. The rate of change of digital signals between High and low level is?

very fast

fast

slow

very slo

49. Digital circuits mostly use?

Diodes

Bipolar transistors

Diodes and bipolar transistor

Bipolar transistors and FETs

50. Two voltages are-5V and-10V.In positive logic?

-5V is 1 and -10V is 0

-10 Vis 1 and-5V is 0

-5V is 1 and -10V is1

-5V is 0 and -10V is 0

51. Logic Pulser ?

generate short duration pulses

generate long duration pules

generate ideal pulses

None of these

52. The number of LED displays in duration in logic probe are?

1

2

4

1 or 2

53. The output impenitence of a logic pulser is?

Low

High

May be low or high

Can't say

54. A current transducer respond to?

steady current only

pulsating current only

both pulasting and steady

none of these

55. .Logic analyser is?

a multi channel oscilloscope

similar to logic pulser

similar to current tracer

none of above

56. Which of these are two state device?

Lamp

magnetic tap

punched card

All the above

57. In the decimal number 27,the digit 2 represent ?

2

0.2

20

200

58. In Hexadecimal number system,A is equal to decimal number?

10

17

11

18

59. Hexadecimal number F is equal to octal number?

15

17

16

18

60. Hexadecimal number E is equal to binary?

1110

1001

1111

1101

61. Binary number 1101 is equal to octal number?

17

15

16

14

62. octal number 12 is equal to decimal number?

8

9

11

10

63. 100101 is equal to decimal number ?

27

37

17

47

64. Decimal number 10 is equal to binary number?

1110

1001

1010

1000

65. Decimal number 110011011001 is equal to decimal number?

3289

1289

2289

289

66. Which of the following is the ideal characteristics of OP-AMP

Bandwidth is zero

Offset voltage is infinite

Output voltage is infinite

CMMR is infinite

67. A signal has frequency components from 300Hz to 2 kHZ.The minimum possible rate at

which the signal has to be sampled

600Hz

900Hz

2kHz

4Khz

68. Negative feed back in amplifiers is used to

Improves the SNR at the input

Improves the SNR at the output

Reduces distortion

Doesn’t effect the SNR at the output

69. In PCM system, if the quantization levels are increased from 2 to 8, the relative bandwidth

requirement will.

remain same

be doubled

be tripled

become four times

70. Fulladder consists of

1 half adder and 1 AND gate

2 Half adders and 1 XOR gate

1 Half adder and 1 OR gate

2 Half adders and 1 OR gate

71. Flipflop is a

Monostable

Bistable

Astable

None of these

72. For a 8 bit counter the number of filp flops required is

2

4

3

1

73. In 8085 microprocessor The data bus has

Unidirectional

Bi-directional

Both

None of these

74. The number of hardware interrupts in 8085 Microprocessors

2

4

3

5

75. Which of the following is used for Wider bandwidth in amplifiers

Cascade connection

Darlington

Cascode connection

Both A and B

76. When modulation changed from 0 to 1 then power increases by

20%

40%

50%

90%

77. The highest modulation frequency typically used in AM broadcast is

5KHz

10kHz

15kHz

22kHz

78. Time division multiplexing used in

Analog communication

Digital communication

Both A and B

None of these

79. Gray code is also called as

Cyclic code

Reflected code

Both A and B

None of these

80. Common base amplifier has

High input impedance

High output impedance

Low output impedance

None

81. In negative feedback the distortion will

Increase

Decrease

Some times increase some times decrease

None of the above

82. Barkausens criteria is

Aß=1

Aß=-1

Both A and B

None

83. Which of the following is more stable

Wien bridge oscillator

Crystal oscillator

RC oscillatory

Colpitts Oscillator

84. The forbidden energy gap for germanium atom

1.1 ev

0.7 ev

0.3 ev

None

85. For reflection coefficient ?=0.5,VSWR is

2

3

4

8

86. The unit of µ0e0 is

Farad henry

Meter2/sec2

Amp-sec

None

87. A low loss transmission line has

R=wl, G=wC

R<<wL, G<<wC

R>>wL, G>>wC

None

88. Which of the following has longest wavelength

HF

VHF

UHF

SHF

89. For a good conductor, the skin depth varies:

Directly as frequency f

Directly as √f

Inversely as √f

None

90. .An antenna that is circularly polarized is

Helical

Yagi-uda

Parabolic

Small circular loop

91. In series resonance circuit the voltage source is

Low resistance

High resistance

Zero resistance

None of the above

92. A network is non linear if it doesn’t satisfy

Homogeneity

Superposition theorem

Associative condition

Both A and B

93. The gray code for number 6 is

1100

1001

0101

0110

94. What is the addressing mode used in instruction LDA 0345

Direct

Indirect

Immediate

Indexed

95. How many modes of operations are there in 8255 PPI?

1

2

3

4

96. Which of the following has lowest efficiency

Class A

Class B

Class AB

Class C

97. The differential amplifier has a differential gain of 20000 CMRR=80dB. The common mode

gain is

2

1

0.5

0

98. Super-beta transistor is a

Cascade configuration

Cascode configuration

Darlington configuration

Matched pair

99. To eliminate ghosts in the picture

Use a longer transmission line

Connect a booster

Change the antenna orientation or location

Twist the transmission line

100. Vividh bharati programme is transmitted in

Short waves

Medium frequency

Very high frequency

None

101. The double energy transients occur in the

R-L circuit

R-C circuit

Pure inductive circuit

R-L-C circuit

102. The unit of flux is

Weber

Tesla

Joule

Weber/m2

103. The transfer function H(s)=(s2-5s+100)/s2+5s+100 represents

A high pass filter

A band elimination filter

A resonator

An all pass filter

104. Double spotting in superhetrodyne receiver is caused by

Poor front-end rejection

Misalignment of receiver

Detuning of one or more IF stages

Non-functioning of AGC

105. The ratio of distance between cochannel to radius of the cell (D/R)is

N

√N

3√N

√(3N)

106. MAHO stands for

Mobile additive hand off

Mobile assisted Hand off

Mounted additive hand off

None of the above

107. Traffic intensity is measured by

Traffic

Erlangs

Seconds

Decibels

108. Frequency selective fading means

Band width of the signal is greater than the band width of the channel

Delay speed is greater than symbol speed

Both A and B

None of these

109. HLR stands for

Home localized rectifier

Home location register

Home loyality register

None

110. A receiver has poor if selectivity,it will therefore also have poor

Blocking

Double spotting

Diversity reception

Sensitivity

111. The number of lines per second in the US monochrome TV system

31,500

15,750

63.5

525

112. An LED made using GaAs emits radiation in

Visible region

Ultraviolet region

Infrared region

Microwave frequency region