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Class XII Physics Communication Systems 1

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Question 1

In a common base amplifier, the phase difference between input and output is

Question 2

If the lattice constant of this semiconductor is decreased, then which of the following is correct ?

Question 3

Direction : The question has Statement – 1 and Statement – 2. Of the four choices given after the statements, choose the one that describes the two statements.
Statement – 1: 
Skywave signals are used for long distance radio communication. These signals are in general, less stable than ground wave signals.
Statement – 2: The state of ionosphere varies from hour to hour, day to day and season to season.

Question 4

In amplitude modulation, sinusoidal carrier frequency used is denoted by and the signal frequency is denoted by. The bandwidth of the signal is such that. Which of the following frequencies is not contained in the modulated wave?

Question 5

Sinusoidal carrier voltage of frequency 1.5 MHz and amplitude 50V is amplitude modulated by sinusoidal voltage of frequency 10 kHz producing 50% modulation. The lower and upper-side-band frequencies in kHz are

Question 6

An AM wave has 1800 W of total power content. For 100% modulation the carrier should have power content equal to

Question 7

The total power content of an AM wave is 900 W. For 100% modulation, the power transmitted by each side band is

Question 8

With respect to reflection of electromagnetic waves select the false statement
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Aug 17JEE & BITSAT