CBSE Class 12 Physics Principles Of Communication chapter notes and important questions

CBSE Class 12 Physics Principles Of Communication chapter notes and important questions. There are many more useful educational material which the students can download in pdf format and use them for studies. Study material like concept maps, important and sure shot question banks, quick to learn flash cards, flow charts, mind maps, teacher notes, important formulas, past examinations question bank, important concepts taught by teachers. Students can download these useful educational material free and use them to get better marks in examinations.  Also refer to other worksheets for the same chapter and other subjects too. Use them for better understanding of the subjects.

PRINCIPLES OF COMMUNICATION

GIST:

1. Basic terminology used in Communication:

• Signal: - Electrical form of message suitable for transmission and reception.

• Transducer: - A device which converts one form of energy into another form. e.g., Microphone, Loud speaker, Photo detector etc.

• Noise: - Unwanted signals that tend to disturb the transmission and processing of message signals in a communication system.

• Attenuation: - The loss of strength of a signal while propagation through a medium.

• Amplification: - It is the process of increasing the amplitude of a signal using an electronic circuit.

• Bandwidth: - It refers to the range of frequencies over which equipment operates or portion of the spectrum occupied by the signal.

• Transmitter: - The function of the transmitter is to transmit the modulated signal.

• Receiver: - The function of the receiver is to receive the transmitted signal.

• Demodulator: - It separates the base band signal from the modulated wave.

• Repeater: - It receives the modulated wave and amplify it ,then retransmit so as to increase the range of communication. 

2. Bandwidth of signals

• For Speech signals: 2800 Hz.

• For Music: 20 KHz.

• For Video signals: 4.2 MHz

• For T.V. signals: 6 MHz

3. Bandwidth of transmission medium

• Coaxial cable 750 MHz and are operated below 18 GHz.

• Optical fiber 100 GHz.

• Free space. Table 15.2 page no 519 NCERT Book

4. Propagation of electromagnetic waves

• Ground wave:- The waves are of frequency range of 500 kHz-1510 kHz. And propagate along surface of the earth. As the wave glides along the surfac of the earth it induces  harges on the surface and is attenuated as a result of absorption of energy by the earth

Drawbacks: -

1. Cannot be transmitted over long distances due to attenuation.

2. High frequencies cannot be transmitted due to increased attenuation.

• Sky wave: - This mode of communication is used for frequency range 30 to 40 MHz.Long distance communication can be achieved by ionospheric reflection of radio waves back towards the earth. The sky wave communication cannot be used for the frequency more than 30 MHz because frequencies higher than 30 MHz penetrate the ionosphere and escape.

• Space wave communication: - Communication along a straight line fromtransmitting antenna to the receiving antenna. This is also called LOS communication. Microwaves are used in this mode due to their directional property. Diagram 15.5 page no 521  

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