Creating AM

Q.

How does electromagnetic waves carry digital data?

Q.

AM is used for broadcasting because

1. It is more noise immune than other modulation systems

2. It requires less transmitting power compared with other systems

3. Its use avoids receiver's complexity

4. No other modulation system can provide the necessary bandwidth faithful transmission

Q. The electron density of E, $F_1$ , $F_2$ layers of ionosphere is 2 $\times {10}^{11}$, 5 $\times {10}^{11}$ and 8 $\times {10}^{11}$ $m^{-3}$ respectively. What is the ratio of critical frequency for reflection of radiowaves

1. 2 : 4 : 3
2. 4 : 3 : 2
3. 2 : 3 : 4
4. 3 : 2 : 4

Q. A transmitter supplies 9 kW to the aerial when unmodulated. The power radiated when modulated to 40% is

1. 5 kW
2. 9.72 kW
3. 10 kW
4. 12 kW

Q. If a number of sine waves with modulation indices $n_1,n_2,n_3$........ modulate a carrier wave, then total modulation index (n) of the wave is

1. $n_1+n_2$ + .. +2 ($n_1,n_2+..$)
2. $\sqrt{n_1-n_2+n_3..}$
3. $\sqrt{{n_1}^2+{n_2}^2+{n_3}^2+..}$
4. None of these

Q. An antenna current of an AM broadcast transmitter modulated by 50% is 11 A. The carrier current is

1. 10.35 A
2. 9.25 A
3. 10 A
4. 5.5 A

Q. What is the modulation index of an over modulated wave

1. 1
2. >1
3. <1
4. Zero

Q. In an amplitude modulated wave for audio frequency of 500 cycle/second, the appropriate carrier frequency will be

1. 50 cycles/sec
2. 100 cycles/sec
3. 500 cycles/sec
4. 50, 000 cycles/sec

Q.

The process of superimposing signal frequency (i.e. audio wave) on the carrier

wave is known as [AIIMS 1987]

1. Transmission

2. Reception

3. Modulation

4. Detection

Q. The electron density of E, $F_1$ , $F_2$ layers of ionosphere is 2 $\times {10}^{11}$, 5 $\times {10}^{11}$ and 8 $\times {10}^{11}$ $m^{-3}$ respectively. What is the ratio of critical frequency for reflection of radiowaves

1. 2 : 4 : 3
2. 4 : 3 : 2
3. 2 : 3 : 4
4. 3 : 2 : 4

Q. A neutral pendulum oscillates in a uniform electric field as shown in the figure. If a positive charge is given to the pendulum, then its time period

1. first increases and then decreases
2. increases
3. remains constant
4. decreases