Test: Communication Systems - JEE MCQ

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.

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).

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.

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

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.
 

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.

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..

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.
2.AM radio
3.Formerly used to squeeze much mp3 music onto floppy disk & very small mp3 players.
 

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.

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.

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

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.

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.

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.

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.

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= A_m​​/A_c​
Am​=0.75×12
So, A_m​=9 V

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.

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.

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

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

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.

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.