Engineering Entrance Sample Papers

Communication System class 12 important questions

MCQ on Communication System
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MCQ on Communication System

Question 1
An amplitude modulated wave is modulated to 50%. What is the saving in power if carrier as well as one of the side bands are suppressed

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A
65.4%
B
94.4%
C
70%
D
25.5%
Question 2
The bit rate for a signal, which has a sampling rate of 8 kHz and where 16 quantisation levels have been used is
A
72000 bits/sec
B
32000 bits/sec
C
64000 bits/sec
D
16000 bits/sec
Question 3
Maximum useable frequency (MUF) in F-region layer is x, when the critical frequency is 60 MHz and the angle of incidence is 70°. Then x is
A
150 MHz
B
170 MHz
C
190 MHz
D
175 MHz
Question 4
A laser beam is used for carrying out surgery because it
A
is highly monochromatic
B
is highly coherent
C
is highly directional
D
can be sharply focussed
Question 5
While tuning in a certain broadcast station with a receiver, we are actually?
A
Varying the local oscillator frequency
B
Tuning the antenna
C
None of these
D
Varying the frequency of the radio signal to be picked up
Question 6
Long distance short-wave radio broadcasting uses

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A
Direct wave
B
Sky wave
C
Ionospheric wave
D
Ground wave
Question 7
In which of the following remote sensing technique is not used

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A
Medical treatment
B
Pollution
C
Wetland mapping
D
Forest density
Question 8
AM is used for broadcasting because
A
It requires less transmitting power compared with other systems
B
It is more noise immune than other modulation systems
C
Its use avoids receiver complexity
D
No other modulation system can provide the necessary bandwidth faithful transmission
Question 9
In a communication system, noise is most likely to affect the signal
A
In the information source
B
In the channel or in the transmission line
C
At the transmitter
D
At the receiver
Question 10
In short wave communication waves of which of the following frequencies will be reflected back by the ionospheric layer, having electron density 1011 per m
A
10 MHz
B
18 MHz
C
12 MHz
D
2 MHz
Question 11
Basically, the product modulator is

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A
A phase separator
B
An amplifier
C
A mixer
D
A frequency separator
Question 12
Through which mode of propagation, the radio waves can be sent from one place to another
A
Ground wave propagation
B
Space wave propagation
C
All of them
D
Sky wave propagation
Question 13
Advantage of optical fibre
A
High bandwidth, high data transmission capacity and no EM interference
B
High band width, low transmission capacity and no EM interference
C
High bandwidth and EM interference
D
Low bandwidth and EM interference
Question 14
Audio signal cannot be transmitted because
A
The signal has more noise
B
The transmitting antenna length is very large and impracticable
C
The transmitting antenna length is very small to design
D
The signal cannot be amplified for distance communication
Question 15
The total power content of an AM wave is 1500 W. For 100% modulation, the power transmitted by the carrier is
A
500 W
B
1000 W
C
700 W
D
750 W
There are 15 questions to complete.
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Vishal Arora

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