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NEET

Explore popular questions for NEET. This collection includes questions from Physics, Chemistry, Biology. They're hand picked by top teachers from a vast pool of questions including previous year NEET questions.

Q 1.

Correct4

Incorrect-1

Communication is the process of

A

keeping in touch

exchange information

C

broad casting

D

entertainment by electronics

Explanation

Q 2.

Correct4

Incorrect-1

Which of the following is the element of a communication system?

A

Transmitter

B

channel

C

Receiver

All of the above

Explanation

Q 3.

Correct4

Incorrect-1

A transducer used at the transmitting end, serves the purpose of converting

A

electrical signal to sound form

sound signal to electrical form

C

electrical signal to magnetic form

D

sound signal to magnetic form

Explanation

Q 4.

Correct4

Incorrect-1

The term channel is used to indicate

A

the amplitude range allocated to a given source

the frequency range allocated to a given source

C

the voltage-range allocated to a given source

D

All of the above

Explanation

Q 5.

Correct4

Incorrect-1

Buffer amplifier is used at the transmitting end to

A

feed carrier frequency to master oscillator

B

amplify carrier frequency

C

mix modulating signal with carrier frequency

isolate master oscillator from other stages of transmitter.

Explanation

Q 6.

Correct4

Incorrect-1

The purpose of a detector at the receiving end is

A

to amplify signal

B

to reduce its frequency level

C

to modulate signal

to demodulate signal

Explanation

Q 7.

Correct4

Incorrect-1

As the height of the satellite, orbit gets lower, the speed of the satellite

A

increases

decreases

C

remain same

D

both (a) and (b)

Explanation

With decrease in 'r' velocity of satellite increases

Q 8.

Correct4

Incorrect-1

A {tex} 1 \mathrm { kW } {/tex} carrier is modulated to a depth of {tex} 80 \% . {/tex} The total power in the modulated wave is

1.32

B

1.56

C

1.84

D

1.96

Explanation

Q 9.

Correct4

Incorrect-1

If the heights of transmitting and the receiving antennas are each equal to {tex} h , {/tex} the maximum line-of-sight distance between them is (R is the radius of earth)

A

{tex} \sqrt { 2 \mathrm { Rh } } {/tex}

B

{tex} \sqrt { 4 \mathrm { Rh } } {/tex}

C

{tex} \sqrt { 6 \mathrm { R } h } {/tex}

{tex} \sqrt { 8 \mathrm { R } h } {/tex}

Explanation

Q 10.

Correct4

Incorrect-1

For sky wave propagation of a {tex} 10 \mathrm { MHz } {/tex} signal, what should be the minimum electron density in ionosphere

{tex} \sim 1.2 \times 10 ^ { 12 } \mathrm { m } ^ { - 3 } {/tex}

B

{tex} \sim 10 ^ { 6 } m ^ { - 3 } {/tex}

C

{tex} \sim 10 ^ { 14 } \mathrm { m } ^ { - 3 } {/tex}

D

{tex} \sim 10 ^ { 22 } \mathrm { m } ^ { - 3 } {/tex}

Explanation

Q 11.

Correct4

Incorrect-1

The electron density of a layer of ionosphere at a height {tex} 150 \mathrm { km } {/tex} from the earth's surface is {tex} 9 \times 10 ^ { 9 } {/tex} per {tex} \mathrm { m } ^ { 3 } . {/tex} For the sky transmission from this layer up to a range of {tex} 250 \mathrm { km } {/tex}, The critical frequency of the layer is

A

{tex} 2 \ \mathrm { Hz } {/tex}

B

{tex} 2.7\ \mathrm { Hz } {/tex}

C

{tex} 2.78\ \mathrm { kHz } {/tex}

{tex} 2.7 \ \mathrm { MHz } {/tex}

Explanation

Q 12.

Correct4

Incorrect-1

An AM- signal is given as
{tex}X_\mathrm {AM} (t) = 100 [p(t) + 0.5g(t)]cos \omega_c t{/tex} in interval {tex} 0\leq t\leq 1 {/tex}. One set of possible values of the modulating signal and modulation index would be

{tex} t , 0.5 {/tex}

B

{tex} t , 1.0 {/tex}

C

{tex} t , 1.5 {/tex}

D

{tex} t ^ { 2 } , 2.0 {/tex}

Explanation

Q 13.

Correct4

Incorrect-1

Calculate the power developed by an amplitude modulated wave in a load resistance of {tex} 100 \Omega , {/tex} if the peak voltage of carrier wave is {tex} 100 \mathrm { V } {/tex} and modulation index is {tex} 0.4 . {/tex}

A

{tex} 50 \ \mathrm { watt } {/tex}

{tex} 54\ \mathrm { watt } {/tex}

C

{tex} 104 \ \mathrm { watt } {/tex}

D

{tex} 4 \ \mathrm { watt } {/tex}

Explanation

Q 14.

Correct4

Incorrect-1

In an FM system a {tex} 7 \mathrm { kHz } {/tex} signal modulates {tex} 108 \mathrm { MHz } {/tex} carrier so that frequency deviation is {tex} 50 \mathrm { kHz } {/tex}. The carrier swing is

{tex}7.1{/tex}

B

{tex}2.8{/tex}

C

{tex}5.8{/tex}

D

{tex}3.2{/tex}

Explanation

Q 15.

Correct4

Incorrect-1

If {tex} \mathrm { E } _ { \mathrm { c } } = 20 \sin 10 ^ { 5 } \pi \mathrm { t } {/tex} and {tex} \mathrm { E } _ { \mathrm { m } } = 10 \sin 400 \pi \mathrm { t } {/tex} are carrier and modulating signals, the modulation index is:

A

{tex} 56 \% {/tex}

B

{tex} 30 \% {/tex}

{tex} 50 \% {/tex}

D

{tex} 48 \% {/tex}

Explanation

Q 16.

Correct4

Incorrect-1

A tuned amplifier circuit is used to generate a carrier frequecy of {tex} 2 \mathrm { MHz } {/tex} for the amplitude modulation. The value of {tex} \sqrt { \mathrm { LC } } {/tex} is:

A

{tex} \frac { 1 } { 3 \pi \times 10 ^ { 6 } } {/tex}

B

{tex} \frac { 1 } { 2 \pi \times 10 ^ { 6 } } {/tex}

{tex} \frac { 1 } { 4 \pi \times 10 ^ { 6 } } {/tex}

D

{tex} \frac { 1 } { 2 \times 10 ^ { 6 } } {/tex}

Explanation

Q 17.

Correct4

Incorrect-1

The maximum range for the tropospheric transmission of radio wave of wavelength {tex} 3 \mathrm { m } {/tex} using the transmitting antenna and receiving antenna of hights {tex} 100 \mathrm { m } {/tex} and {tex} 60 \mathrm { m } {/tex} respectively is

A

{tex} 8 \mathrm { m } {/tex}

B

{tex} 800 \mathrm { m } {/tex}

{tex} \mathrm { 8km } {/tex}

D

{tex} 80 \mathrm { km } {/tex}

Explanation

Q 18.

Correct4

Incorrect-1

The velocity of all radio waves in free space is {tex} 3 \times 10 ^ { 8 } \mathrm { m } / \mathrm { s } {/tex}. What is the frequency of a radio wave of wavelength {tex} 150 \mathrm { m } {/tex}.

A

{tex} 5 \ \mathrm { MHz } {/tex}

{tex} 2 \ \mathrm { MHz } {/tex}

C

{tex} 0.5 \ \mathrm { MHz } {/tex}

D

{tex} 0 \ \mathrm { MH z}{/tex}

Explanation

Q 19.

Correct4

Incorrect-1

Determine the modulation index {tex} \left( \mathrm { m } _ { \mathrm { f } } \right) {/tex} and carrier swing {tex}\mathrm {(S)}{/tex} of an {tex} \mathrm { FM } {/tex} carrier having a frequency deviation of {tex} 25 \mathrm { kHz } {/tex} and a modulating signal of {tex} 5 \mathrm { kHz } {/tex}.

A

{tex} m _ { f } = 3 {/tex}

{tex} m _ { f } = 5 {/tex}

C

{tex} m _ { f } = 8 {/tex}

D

{tex} m _ { f } = 9 {/tex}

Explanation

Q 20.

Correct4

Incorrect-1

{tex} 1000 \mathrm { KHz } {/tex} carrier wave is amplitude modulated by the signal frequency {tex} 200 - 4000 \mathrm { Hz } {/tex}. The channel width of this case is:

{tex} 8 \ \mathrm { KHz } {/tex}

B

{tex} 4 \ \mathrm { KHz } {/tex}

C

{tex} 7.6 \ \mathrm { KHz } {/tex}

D

{tex} 3.8 \ \mathrm { KHz } {/tex}

Explanation

Q 21.

Correct4

Incorrect-1

Maximum usable frequency (MUF) in F-region layer is {tex} x , {/tex} when the critical frequency is {tex} 60 \mathrm { MHz } {/tex} and the angle of incidence is {tex} 70 ^ { \circ } . {/tex} Then calculate {tex} x . {/tex}

A

{tex} 122 \mathrm { MHz } {/tex}

B

{tex} 216 \mathrm { Hz } {/tex}

{tex} 175 \mathrm { MHz } {/tex}

D

{tex} 75 \mathrm { H z} {/tex}

Explanation

Q 22.

Correct4

Incorrect-1

A carrier frequency of {tex} 1 \mathrm { MHz } {/tex} and peak value of {tex} 10 \mathrm { V } {/tex} is amplitude modulated with a signal frequency of {tex} 10 \mathrm { kHz } {/tex} with peak value of {tex} 0.5 \mathrm { V } {/tex}. Then, the modulation index and the side band frequencies respectively are

{tex}0.05{/tex} and {tex} 1 \pm 0.010 \ \mathrm { MHz } {/tex}

B

{tex}0.5{/tex} and {tex} 1 \pm 0.010 \ \mathrm { MHz } {/tex}

C

{tex}0.5{/tex} and {tex} 1 \pm 0.005 \ \mathrm { MHz } {/tex}

D

{tex}0.05{/tex} and {tex} 1 \pm 0.005\ \mathrm { MHz } {/tex}

Explanation

Q 23.

Correct4

Incorrect-1

The antenna current of an AM transmitter is 8 when only the carrier is sent, but it increases to 8.93 when the carrier is modulated by a single sine wave. Find the percentage modulation.

{tex} 60.1 \% {/tex}

B

{tex} 70.1 \% {/tex}

C

{tex} 80.1 \% {/tex}

D

{tex} 50.1 \% {/tex}

Explanation

Q 24.

Correct4

Incorrect-1

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

A

{tex}50{/tex} cycles/s

B

{tex}100{/tex} cycles/s

C

{tex}500{/tex} cycles/s

{tex} 50,000 {/tex} cycles/s

Explanation

In this modulation, the audio frequency wave is superimposed on a high frequency carrier wave in a manner that the frequency of modulated wave is 100 times as that of the carrier wave, but its amplitude is made proportional to the instantaneous amplitude of the audio frequency wave. Thus, the appropriate carrier frequency will be 50000 cycles/second

Q 25.

Correct4

Incorrect-1

A {tex} 10 \mathrm { kW } {/tex} transmitter emits radio waves of wavelength {tex}500 \mathrm { m } . {/tex} The number of photons emitted per second by the transmitter is of the order of

A

{tex} 10 ^ { 37 } {/tex}

{tex} 10 ^ { 31 } {/tex}

C

{tex} 10 ^ { 25 } {/tex}

D

{tex} 10 ^ { 43 } {/tex}

Explanation