Communication system

Communication-system Class 12 MCQs Questions with Answers

Question 1.
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

Question 2.
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

Question 3.
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

Question 4.
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

Question 5.
The wavelength of a wave of frequency 10 kHz is:
(a) 30 m
(b) 300 m
(c) 30 km
(d) 300 km

Question 6.
The area served by an antenna of height 100 m is:
(a) 10⁹m²
(b) 4 × 10⁹ m²
(c) 6 × 10⁹m²
(d) 8 × 10¹⁰m²

Question 7.
Which of the following is not transducer?
(a) Loudspeaker
(b) Amplifier
(c) Microphone
(d) All

Question 8.
The space waves which are affected seriously by atmospheric conditions are:
(a) MF
(b) HUF
(c) VHF
(d) UHF

Question 9.
An antenna is:
(a) Inductive
(b) Capacitive
(c) Resistive
(d) A transformer

Question 10.
Broadcasting antenna are generally:
(a) Ommi directional type
(b) Vertical type
(c) Horizontal type
(d) None

Question 11.
The modulation index in amplitude modulation is:
(a) Always zero
(b) Between 0 and 1
(c) Between 1 and ∞
(d) None of these

Question 12.
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)

Question 13.
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

Question 14.
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)

Question 15.
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)

Question 16.
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)

Question 17.
The length of a half wave dipole at 30 mega-hertz is:
(a) 5 m
(b) 10 m
(c) 25 m
(d) 80 m

Question 18.
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

Question 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)

Question 20.
Which is more advantageous?
(a) analog data communication
(b) digital data communication
(c) both (a) and (b) are equally good
(d) depends on the situation

Question 21.
Communication channel consists of:
(a) transmission line only
(b) optical fibre only
(c) free space only
(d) All of the above

Question 22.
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

Question 23.
Digital signals:
(a) represents values as discrete steps
(b) Do not represents values as discrete steps
(c) represent values steps
(d) represent random steps

Question 24.
Digital signals:
(a) deal with all sort of values
(b) can use decimal system
(c) can use binary system
(d) (b) and (c) both

Question 25.
Increase in frequency deviation results into:
(a) increase in noise of FM receiver
(b) decrease in noise of AM receiver
(c) increase in noise of Am receiver
(d) decrease in noise of FM receiver