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Sunday, January 22, 2017

Physics Test Paper (XII)

CLASS - XII PHYSICS (Communication System)

1. A T.V. tower has a height of 300m. What is the maximum distance upto which the T.V transmission can be received?

2. Why ground wave propagation is not suitable for high frequencies?

3. What type of modulation is used for commercial broadcast of voice signal?

4. What is the role of F2 layer in communication?

5. 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%?

6. Give the set up of a basic communication system?

7. Distinguish between analog and digital communication?

8. Define the following terms
(a) Ground wave propagation
(b) Space wave propagation
(c) Sky wave propagation

9. Which two communication methods make use of space wave propagation method? If the sum of the heights of transmitting and receiving antenna is line of sight communication is fixed at h, show that the range is maximum when the two antenna have a height 2h each?

10. A frequency modulated wave is represented by an equation: V = 30 sin (20t + 100)
Find (1) carrier frequency
(2) modulating signal frequency
(3) Power dissipated if load resistor is of 100W?

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