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# Test: Communication Systems (CBSE Level With Solutions)

## 30 Questions MCQ Test Exclusive Video Lectures of Class 12 Physics by Experts | Test: Communication Systems (CBSE Level With Solutions)

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This mock test of Test: Communication Systems (CBSE Level With Solutions) for Class 12 helps you for every Class 12 entrance exam. This contains 30 Multiple Choice Questions for Class 12 Test: Communication Systems (CBSE Level With Solutions) (mcq) to study with solutions a complete question bank. The solved questions answers in this Test: Communication Systems (CBSE Level With Solutions) quiz give you a good mix of easy questions and tough questions. Class 12 students definitely take this Test: Communication Systems (CBSE Level With Solutions) exercise for a better result in the exam. You can find other Test: Communication Systems (CBSE Level With Solutions) extra questions, long questions & short questions for Class 12 on EduRev as well by searching above.
QUESTION: 1

### Electronic communication refers to

Solution:

Explanation:When information are sent from one point  to the other it has to be converted into electrical signal using transducer.The receiver receives it in its original from using receiver.Such from of communication is called electronic communication.

QUESTION: 2

### FM Radio set used in cars is

Solution:

Explanation: Radio means sending energy with waves. In other words, it's a method of transmitting electrical energy from one place to another without using any kind of direct, wired connection. That's why it's often called wireless. The equipment that sends out a radio wave is known as a transmitter; the radio wave sent by a transmitter whizzes through the air—maybe from one side of the world to the other—and completes its journey when it reaches a second piece of equipment called a receiver((here a radio).

QUESTION: 3

### For a signal to be reproduced without distortion

Solution:

Most vibrating objects have more than one resonant frequency and those used in musical instruments typically vibrate at harmonics of the fundamental. A harmonic is defined as an integer (whole number) multiple of the fundamental frequency.

QUESTION: 4

A woofer should be fed from the input through a

Solution:

Woofer is a low frequency loud speaker covering the range 16 Hz to 500 Hz.

QUESTION: 5

AM detection is

Solution:

AM Detector. The detection of AM radio signals is a diode application. The modulated AM carrier wave is received by the antenna of the radio receiver and is rectified by the action of a detector diode. The signal frequency which modulates it is much lower, 0.02 to 5 kHz, and it can pass through the filter.

QUESTION: 6

The three elements of a generalized communication system are

Solution:

Explanation:In communication the Transmitter helps in transmitting the signal through communication channel which acts as a physical path that connects transmitter to a receiver.And the receiver receives the transmitted signal and converts those signals in their original form.

QUESTION: 7

TV set used in a typical house is

Solution:

Explanation: The equipment that sends out a radio wave is known as a transmitter; the radio wave sent by a transmitter whizzes through the air—maybe from one side of the world to the other—and completes its journey when it reaches a second piece of equipment called a receiver.A television antenna, or TV aerial, is an antenna specifically designed for the reception of over-the-air broadcast television seignal, which are transmitted at frequencies from about 41 to 250 MHz in the VHF band, and 470 to 960 MHz in the UHF band in different countries..

QUESTION: 8

Audio signals have a maximum bandwidth of about

Solution:

22050Hz (often lazily called "22 kHz") has been a reasonably popular sample rate for low bit rate MP3s such as 64 kbps in years past. Audio quality is significantly affected, with higher frequency content missing. With the general rise in the availability of large file storage space and faster data links, 22 kHz is now of more limited use.
1.For speech recording where perceived quality is unimportant, but clarity must be maintained.
3.Formerly used to squeeze much mp3 music onto floppy disk & very small mp3 players.

QUESTION: 9

Pulse is specified by pulse height or the peak voltage, the pulse duration and pulse to pulse spacing. In pulse amplitude modulation (PAM) what changes with base band signal is

Solution:

Pulseis specified by pulse height or the peak voltage, the pulse duration and pulse to pulse spacing. In pulse amplitude modulation (PAM) what changes with base band signal is pulse height or the peak voltage.
Hence the correct answer is option D.

QUESTION: 10

A rectifier and an envelope detector for AM uses

Solution:
QUESTION: 11

Electronic communication is not possible if

Solution:

Explanation:As the information or message is transmitted from the source to the receiver ,it is first converted into electrical signal which is then transmiited through the communication medium.Hence in electrical communication it is must to convert raw message or information into electrical signal.Else the electronic messages will not be transmitted.

QUESTION: 12

For attenuation of high frequencies we should use

Solution:

Since Xc for high frequencies is low, the high frequencies are shunted to ground and are not transmitted.

QUESTION: 13

Coaxial cables have a bandwidth in the range of

Solution:
QUESTION: 14

To reduce the distortion in amplitude modulation, modulation index is kept

Solution:

In Amplitude modulation, it is defined as the ratio of the amplitude of modulating signal to that of the carrier signal. Its value is kept less than 1 to avoid overmodulation which leads to distortions in the modulated signal and makes it very hard to demodulate and extract the modulating signal.

QUESTION: 15

Frequencies in the UHF range normally propagate by means of:

Solution:
QUESTION: 16

Which of these is an example of point to point communication?

Solution:

Explanation:In point to point communication,communication occurs over a link between a single transmitter and receiver.Telephony is an example of it as it needs a link between caller and receiver to transmit the information.This link is provided by various media like cable.

QUESTION: 17

Amplification is the

Solution:

Explanation:It is the process of increasing the amplitude and hence the strength of an elctrical signal by using an electric circuit having atleat on transistor is called amplifier.Amplification is rerquired to compensate for the loss of strenght of a signal during its transmission.The additional energy is otianed from a dc source.The process of amplification is done at a location betwen the sources and the destination where the strength of signal becomes weaker than the required level.

QUESTION: 18

Transmission bandwidth of fiber optic communication can be up to

Solution:
QUESTION: 19

One method of producing an amplitude modulation is to add the carrier and modulating signal and then

Solution:

a square law device is used, to eliminate the need of generating a carrier at the receiver end as a demodulator. the result of a square law will have the desired component as well as harmonics. To suppress these harmonics, a bandpass filter (sometimes low pass) is used.

QUESTION: 20

A carrier wave of peak voltage 12V is used to transmit a message signal. What should be the peak voltage of the modulating signal in order to have a modulation index of 75%?

Solution:

The peak voltage of the carrier wave is, Ac​=12 V
Modulation index, m=0.75
The peak voltage for the modulating signal is given by:
m= Am​​/Ac
Am​=0.75×12
So, Am​=9 V

QUESTION: 21

Which of these is an example of broadcast communication?

Solution:

Explanation:In broadcast mode of communication a large number of receivers are linked to a single transmiiter.Radio works as receiver which converts the transmiited information/message into the original form of the information.

QUESTION: 22

Range of an electronic communication system

Solution:

Explanation:As the distance between the source and the destination increases the strenght of the transmitted signals become weaker and weaker and the distance where it loses energy to travel any more is range of the signal.

QUESTION: 23

In ground wave propagation the earth

Solution:
QUESTION: 24

Before transmission the AM produced by a square law device

Solution:

Before transmission the AM produced by a square law device goes through a power amplifier.

QUESTION: 25

Multiplexing is a scheme for transmitting multiple signals at the same time e.g. speeches of ten persons in different rooms on the same channel. How many transmitters will be required in any multiplexing scheme?

Solution:

The transmitter required is only one.because the signal needed to be transmitted is one.

QUESTION: 26

Transducer is a device that

Solution:

Explanation:Any device which converts energy from one form to another is called a transducer.It converts variation in physical quantities such as pressure,dispalcement,force,temprature etc.Like microphone converts sound signal into an electrical signal.

QUESTION: 27

Bandwidth of an electronic communication system

Solution:

Explanation: A range within a band of wavelengths, frequencies, or energies; especially :  a range of radio frequencies which is occupied by a modulated carrier wave, which is assigned to a service, or over which a device can operate.

QUESTION: 28

Ground wave propagation is used for

Solution:
QUESTION: 29

The range of an AM broadcast depends

Solution:
QUESTION: 30

In Amplitude modulation if one of the two side bands is removed by a filter is it possible to recover the modulating signal?

Solution: