NCERT Solutions for class 12 Physics | Chapter 15 - Communication Systems

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Questions
1 Which of the following is not transducer?
A Loudspeaker
B Amplifier
C Microphone
D All

Answer:Amplifier
2 The length of a half wave dipole at 30 mega-hertz is:
A 5 m
B 10 m
C 25 m
D 80 m

Answer:5 m
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3 Name the man who was first to place his foot on the moon and in which year:
A Neil Armstrong, 1969
B James Van A lien, 1971
C Leonov, 1965
D None of these

Answer:Neil Armstrong, 1969
4 A loudspeaker converts:
A electrical signals into sound signals
B sound signals into electrical signals
C both (a) and (b)
D neither (a) nor (b)

Answer:electrical signals into sound signals
5 In space communication, the sound waves can be sent from one place to another:
A through space
B through wires
C by superimposing it on undamped electro-magnetic waves
D by superimposing it on damped electro-magnetic waves

Answer:by superimposing it on undamped electro-magnetic waves
6 A microphone converts:
A sound signals into electrical signals
B electrical signals into sound signals
C both (a) and (b)
D Neither (a) nor (b)

Answer:sound signals into electrical signals
7 The modulation index in amplitude modulation is:
A Always zero
B Between 0 and 1
C Between 1 and ∞
D None of these

Answer:Between 1 and ∞
8 The space waves which are affected seriously by atmospheric conditions are:
A MF
B HUF
C VHF
D UHF

Answer:UHF
9 The area served by an antenna of height 100 m is:
A 109m²
B 4 × 109 m²
C 6 × 109m²
D 8 × 1010m²

Answer:4 × 109 m²
10 Broadcasting antenna are generally:
A Ommi directional type
B Vertical type
C Horizontal type
D None

Answer:Vertical type
11 The audio frequencies range from:
A 20 Hz to 20.000 kHz
B 20 Hz to 20 kHz
C 20 kHz to 20.000 kHz
D None of these

Answer:20 Hz to 20 kHz
12 Who undertook the first space walk and in which year?
A Leonov 1965
B Neil Armstrong, 1969
C Rakesh Sharma. 1998
D None of these

Answer:Leonov 1965
13 An antenna is:
A Inductive
B Capacitive
C Resistive
D A transformer

Answer:Inductive
14 The sound produced by a tuning fork is a sort of:
A analog signal
B digital signal
C both (a) and (b)
D neither (a) nor (b)

Answer:analog signal
15 The wavelength of a wave of frequency 10 kHz is:
A 30 m
B 300 m
C 30 km
D 300 km

Answer:30 km
16 The term used “to collect the information about an object and a place without physical contact” is called :
A modulation
B communication
C amplification
D remote sensing

Answer:remote sensing
17 The velocity of electromagnetic wave is:
A 3 × 105 ms-1
B 3 × 106 ms-1
C 3 × 108 ms-1
D 3 × 1010 ms-1

Answer:3 × 108 ms-1
18 The output of a digital computer is an example of:
A digital signal
B analog signal
C both (a) and (b)
D neither (a) nor (b)

Answer:digital signal
19 The output of a digital computer is an example of:
A digital signal
B analog signal
C both (a) and (b) above
D neither (a) nor (b)

Answer:digital signal
20 AM is used for broadcasting because:
A it is more noise immune than other modulation system
B it requires less transmitting power compare with other systems
C its use avoids receiver complexity
D No other modulation system can provide the necessary bandwidth faithful transmission

Answer:its use avoids receiver complexity

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