Tag: elements of a communication system

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Questions Related to elements of a communication system

Multiple choice physics communication system elements of a communication system elements of communication system electromagnetic waves and communication system

The wave used by artificial satellites for communication is

  1. Microwaves

  2. Infrared rays

  3. Radio rays

  4. X-rays
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Microwaves are mostly used for satellite communication, as microwaves can pass straight through the atmosphere and connect antennas on earth to satellite in earth's orbit.

Multiple choice physics communication system elements of a communication system elements of communication system electromagnetic waves and communication system

The critical velocity of satellite of mass $100 kg$ moving round a planet is $20 m/s$. If another satellite of mass $200 kg$ is kept moving in the same orbit then its critical velocity will be:

  1. $40 km/hr$

  2. $72 km/hr$

  3. $40 m/s$

  4. $72 m/s$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The critical velocity (orbital velocity) of a satellite is given by v = sqrt(GM/r). It is independent of the mass of the satellite. Therefore, the velocity remains 20 m/s. Converting 20 m/s to km/hr: 20 * (3600/1000) = 72 km/hr.

Multiple choice physics communication system elements of a communication system elements of communication system electromagnetic waves and communication system

In sky wave communication which of the frequency will be reflected back by the ionospheric layer having electron density $4 \times 10 ^ { 6 } / \mathrm { m } ^ { 3 }$

  1. $19 \times 10 ^ { 3 } \mathrm { Hz }$

  2. $9 \times 10 ^ { 3 } H z$

  3. $31 \times 10 ^ { 3 } \mathrm { Hz }$

  4. $20 \times 10 ^ { 3 } \mathrm { Hz }$
Reveal answer Fill a bubble to check yourself
B Correct answer
Multiple choice physics communication system elements of a communication system elements of communication system electromagnetic waves and communication system

A digital signal

  1. is less reliable than analog signal

  2. is more reliable than analog signal

  3. is equally reliable as the analog signal

  4. Not at all reliable
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Noise is added to digital signal also but its easier to remove the noise and amplify the digital signals as compared to analog signals, because analog signals contain many frequencies.

Multiple choice physics communication system elements of a communication system elements of communication system electromagnetic waves and communication system

Statement A: If the antenna is vertical,a vertically polarised EM wave is radiated
Statement B: The vertically polarised EM wave has electrical variations in the vertical plane

  1. A is true but B is false

  2. A is false but B is true

  3. A and B are false

  4. A and B are true
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Polarization of wave depends upon the orientation of the antenna. direction of polarization is along the orientation of antenna. By convention, direction of polarization of an EM wave is along the variation of electric field.

Multiple choice physics communication system elements of a communication system elements of communication system electromagnetic waves and communication system

An antenna serves the following purpose : 

  1. Converts AF wave to RF wave

  2. Converts RF signal into electromagnetic energy

  3. Converts the guided EM waves into free space EM waves and vice versa

  4. Superimposes AF wave on RF wave
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The antenna serves as the region of transition between guided and free space propagation.

Multiple choice physics communication system elements of a communication system elements of communication system electromagnetic waves and communication system

The concepts of communication are
a) mode of communication
b) need for modulation
c) types of modulation
d) detection of modulated wave

  1. a, b, c are true

  2. b, c, d are true

  3. c, d, a are true

  4. a, b, c & d are true
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In the concept of communication,

(a) Modes of communication are video, audio, face-to-face and text transmission.
(b) Modulation is needed, because original signal doesn't have the power to reach the desired destination, so it is modulated.
(c) Modulation are of different types, as amplitude modulation, frequency modulation and phase modulation etc. 
(d) Detection of modulated wave is done to extract the original signal from modulated wave.

Multiple choice physics communication system elements of a communication system elements of communication system electromagnetic waves and communication system

Buffer amplifier is used at the transmitting end to

  1. feed carrier frequency to master oscillator

  2. amplify carrier frequency

  3. mix modulating signal with carrier frequency

  4. isolate master oscillator from other stages of transmitter.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Displacement current is set up in a region where the electric field is changing with time.

Multiple choice physics communication system elements of a communication system elements of communication system electromagnetic waves and communication system

The science of communication involving long distances is known as

  1. mass-communication

  2. distant-communication

  3. tele-communication

  4. trans-communication
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Telecommunication is the transmission of signs, signals, messages, writings, images and sounds or intelligence of any nature by wire, radio, optical or other electromagnetic systems. Telecommunication occurs when the exchange of information between communication participants includes the use of technology. 
 It is transmitted either electrically over physical media, such as cables, or via electromagnetic radiations.
20th and 21st century technologies for long-distance communication usually involve electrical and electromagnetic technologies, such as telegraph, telephone, and  radio, fiber optics, and communication satellites.