CBSE Class 12 Physics Communication Systems MCQs

Question : Communication is the process of

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

Answer: B 

Question : Which of the following is the element of a communication system?

(a) Transmitter
(b) channel
(c) Receiver     
(d) All of the above

Answer: D 

Question : 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

Answer: B

Question : The term channel is used to indicate

(a) the amplitude range allocated to a given source
(b) the frequency range allocated to a given source
(c) the voltage-range allocated to a given source
(d) All of the above

Answer: B 

Question : 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.

Answer: D 

Question : 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.

Answer: D 

Question :   Wave obtained on superimposition of audible frequency e.m. wave is known as

(a) carrier wave       
(b) high frequency wave
(c) modulating wave
(d) modulated wave

Answer: D 

Question : The AM wave is equivalent to the summation of

(a) two sinusoidal waves
(b) three sinusoidal waves
(c) four sinusoidal waves
(d) None of these

Answer: B 

Question : 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)

Answer: B 

Question : Which of the following is drawback of amplitude modulation?

(a) low efficiency                 
(b) noise reception
(c) operating range is small
(d) all of these

Answer: D

Question : 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.

Answer: A

Question :   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

Answer: D

Question : The service area of space wave communication increases by

(a) increasing the height of transmitting antenna
(b) decreasing the height of receiving antenna
(c) increasing the height of both transmitting and receiving antenna
(d) decreasing the distance between transmitting and  receiving antenna

Answer: C

Question : 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

Answer: D

Question : An audio frequency of 10 kHz is transmitted by SSB after AM with carrier waves of frequency 1MHz. The frequency of current in output load is

(a) 1010 kHz or 990 kHz
(b) 1010 MHz or1010 MHz
(c) 110 kHz or 990 kHz 
(d) 110 MHz or 990 MHz

Answer: A

Question : In an amplitude modulated wave for audio frequency of 500 cycle/second, the appropriate carrier frquency will be

(a) 50 cycles/s  
(b) 100 cycles/s
(c) 500 cycles/s
(d) 50, 000 cycles/s

Answer: D

Question : To cover a population of 20 lakh, a transmission tower should have a height: (radius of the earth = 6400 km, population per square km = 1000)

(a) 25 m
(b) 50 m
(c) 75 m
(d) 100 m

Answer: B

Question : In FM, when frequency deviation is doubled, then

(a) modulation is halved
(b) carrier swing is halved
(c) modulation is doubled
(d) modulation index is decreased

Answer: C

Question :   Television signals are

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

Answer: C

Question :   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.

Answer: D