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Class 12 Physics MCQ Questions of Communication Systems with Answers?

Answer 1

Students can solve these Communication Systems Class 12 MCQ Questions with Answers and assess their preparation level and score high marks in exams. Class 12 Physics MCQ Questions of Communication Systems with Answers available at sarthaks eConnect. Class 12 Physics MCQ Questions with Answers were prepared based on the latest exam pattern.

Learn important MCQ Questions with detailed Solutions for Class 12 for Board Exam. Students preparing for Class 12 Physics Board Exam usually ask about important Multiple Choice Questions. We have provided MCQ Questions for Class 12 Physics with Answers to help students understand the concept very well.

Practice MCQ Question for Class 12 Physics chapter-wise

1. 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

2. Which of the following is not transducer?

(a) Loudspeaker
(b) Amplifier
(c) Microphone
(d) All

3. Broadcasting antenna are generally:

(a) Ommi directional type
(b) Vertical type
(c) Horizontal type
(d) None

4. 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)

5. 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)

6. 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)

7. 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

8. Communication channel consists of:

(a) transmission line only
(b) optical fibre only
(c) free space only
(d) All of the above

9. Digital signals:

(a) represents values as discrete steps
(b) Do not represents values as discrete steps
(c) represent values steps
(d) represent random steps

10. A transducer used at the transmitting end, serves the purpose of converting

(a) electrical signal to sound form
(b) sound signal to electrical form
(c) electrical signal to magnetic form
(d) sound signal to magnetic form

11. Buffer amplifier is used at the transmitting end to

(a) feed carrier frequency to master oscillator
(b) amplify carrier frequency
(c) mix modulating signal with carrier frequency
(d) isolate master oscillator from other stages of transmitter

12. During ground wave propagation the transmitted waves gets attenuated because

(a) earth surface absorbs the waves
(b) frequency of the waves are too low
(c) energy content of these waves are high
(d) earth surface offers resistance

13. For a radio wave reaching the ionised medium

(a) will bend away from normal
(b) will bend towards normal
(c) will bend follow a straight-path
(d) None of these

14. Audio signal cannot be transmitted because

(a) the signal has more noise
(b) the signal cannot be amplified for distance communication
(c) the transmitting antenna length is very small to design
(d) the transmitting antenna length is very large and impracticable

15. 12 signals each band limited to 5 kHz are to be transmitted by frequency-division multiplexer. If AM-SSB modulation guard band of 1 kHz is used then the bandwidth of multiplexed signal is

(a) 101 kHz
(b) 99 kHz
(c) 84 kHz
(d) 71 kHz

16. Television signals are

(a) frequency modulated
(b) amplitude modulated
(c) both frequency and amplitude modulated
(d) phase modulated

17. In PCM if the transmission path is very long

(a) pulse spacing is reduced
(b) pulse amplitude is increased
(c) pulse width is increased
(d) repeater stations are used

18. Communication is the process of

(a) keeping in touch
(b) exchange information
(c) broad casting
(d) entertainment by electronics

19. As the height of satellite orbit gets lower, the speed of the satellite

(a) increases
(b) decreases
(c) remain same
(d) both (a) and(b)

20. Assertion: Radar is used to detect an aeroplane in the sky.

Reason: Radar works on the principle of reflection of waves.

(a) If both the assertion and the reason are true and the reason is a correct explanation of the assertion
(b) If both the assertion and reason are true but the reason is not a correct explanation of the assertion
(c) If the assertion is true but the reason is false
(d) If both the assertion and reason are false

21. In amplitude modulation, the bandwidth is

(a) twice the audio signal frequency
(b) thrice the audio signal frequency
(c) thrice the carrier wave frequency
(d) twice the carrier wave frequency
(e) sum of audio signal frequency and carrier wave frequency

22. If both the length of an antenna and the wavelength of the signal to be transmitted are doubled, the power radiated by the antenna

(a) is doubled
(b) is halved
(c) remains constant
(d) is quadrupled
(e) increases 16 times

23. A modem is a

(a) modulating device only
(b) demodulating device only
(c) modulating and demodulating device
(d) transmitting device
(e) receiving device

24. A repeater is a combination of

(a) receiver and modulator
(b) receiver and transducer
(c) receiver and transmitter
(d) receiver and amplifier
(e) amplifier and transmitter

25. A point-to-point communication mode is seen in

(a) Satellite cable communication
(b) Television transmission
(c) FM radio transmission
(d) AM radio transmission
(e) Fax transmission

Answer 2

1. Answer : (b) 20 Hz to 20 kHz

Explanation: The generally established audio frequency range is 20 Hz to 20,000 Hz, though most people can hear less than this entire range, and as they get older, the range tends to contract on both ends. 

2. Answer : (b) Amplifier

Explanation: Amplifier is not a transducer because it only amplifies the signals. A transducer converts one form of energy to another as in the case of a microphone or a loudspeaker or a photocell.

3. Answer : (b) Vertical type

Explanation: Broadcasting antennas are generally vertical type.

4. Answer : (a) digital signal

Explanation: Examples of digital signals are Computers, Digital Phones, Digital pens, etc.

5. Answer : (a) sound signals into electrical signals

Explanation: A microphone converts sound into a small electrical current. Sound waves hit a diaphragm that vibrates, moving a magnet near a coil. In some designs, the coil moves within a magnet. Other microphones, such as condenser microphones, work on the principle of capacitance.

6. Answer : (a) analog signal

Explanation: The sound signal produced by a tuning fork is only analog.

7. Answer : (c) by superimposing it on undamped electro-magnetic waves

Explanation: In space communication, the sound waves can be sent from one place to another. through space. through wires. by superimposing it on undamped electromagnetic waves.

8. Answer : (d) All of the above

Explanation: These pathways, called communication channels, use two types of media: cable (twisted-pair wire, cable, and fiber-optic cable) and broadcast (microwave, satellite, radio, and infrared). Cable or wire line media use physical wires of cables to transmit data and information.

9. Answer : (a) represents values as discrete steps

Explanation: Digital signals provide discrete values and do not provide a continuous set of values.

10. Answer : (b) sound signal to electrical form

Explanation: The message from the information source may not be in electrical form so to convert these information i.e. in form of sound to electrical form a transducer like a microphone is used.

11. Answer : (d) isolate master oscillator from other stages of transmitter

Explanation: Buffer amplifier isolate master oscillator from the influence of modulation done at a later stage.

12. Answer : (d) earth surface offers resistance

Explanation: During ground wave propagation of radio waves, a charge induced on the Earth's surface which takes the form of current as the wave propagate. The Earth offers resistance in the flow of induced current due to which the waves are attenuated.

13. Answer : (a) will bend away from normal

Explanation: Radio wave enters from an un-ionised medium to an ionised medium, the wave incident on the boundary of the medium deviates from its straight path i.e. will bend away from normal because ionised medium behaves as a rarer medium wr.t. to unionised medium.

14. Answer : (d) the transmitting antenna length is very large and impracticable

Explanation: Audio signals cannot be transmitted as such because the length of transmitting antenna required would be too large and impracticable.

15. Answer : (d) 71 kHz

Explanation: Total signal BW = 12 \(\times\) 5 = 60kHz

11 guard band are required between 12 signal

∴ guard bandwidth =11 \(\times\) 1=11kHz

∴ total bandwidth = 60 + 11= 71kHz

16. Answer : (c) both frequency and amplitude modulated

Explanation: Both audio and video signals are amplitude modulated. Modulation is the process by which some characteristic usually amplitude, frequency or phase angle of a high frequency carrier wave is varied in accordance with the instantaneous value of the low frequency audio signal, called the modulating signal.

17. Answer : (d) repeater stations are used

Explanation: When transmission path is long more repeater stations are needed at intermediate points as repeater receives signal, remove the noise, amplify it and retransmit it along the channel.

18. Answer : (b) exchange information

Explanation: The process of communication refers to the transmission or passage of information or message from the sender through a selected channel to the receiver overcoming barriers that affect its pace.

19. Answer : (b) decreases

Explanation: The orbital velocity of the satellite depends on its altitude above Earth. The nearer to Earth, the faster the required orbital velocity. At an altitude of 124 miles (200 kilometers), the required orbital velocity is a little more than 17,000 mph (about 27,400 kph).

20. Answer : (a) If both the assertion and the reason are true and the reason is a correct explanation of the assertion

Explanation: As radar is most accurate instrument used to detect aeroplane in sky based on principle of reflection of radio waves.

21. Answer : (a) twice the audio signal frequency

Explanation: Modulation is a process of superposing a low frequency audio signals (called modulating signal) on a high frequency radio wave called carrier wave.

Band width = 2 \(\times\) audio signal frequency

22. Answer : (c) remains constant

Explanation: Power radiated by the antenna is proportional to \(\frac{\lambda}{2}\). When both the length of the antenna l and wavelength of the signal \(\lambda\) are doubled, the power radiated by the antenna remains constant.

23. Answer : (c) modulating and demodulating device

Explanation: A modulator-demodulator, or simply modem, is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio.

24. Answer : (c) receiver and transmitter

Explanation: A repeater is a combination of a receiver and a transmitter. A repeater picks up the signal from the transmitter, amplifiers and retransmits it to the receiver while maintaining the strength and data in the signal.

25. Answer : (e) Fax transmission

Explanation: In fax transmission, the information is sent from a source to one receiver through a particular link. Therefore, it can be concluded that a point-to-point communication mode.

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