Semiconductors & Communication · JEE Main previous year questions

2022 29 questions

1. Q372022 · 29 Jul 2022 · Shift 1

   Given below are two statements : One is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Clothes containing oil or grease stains cannot be cleaned by water wash. Reason (R): Because the angle of contact between the oil/grease and water is obtuse. In the light of the above statements, choose the correct answer from the option given below.

   1. A.Both (A) and (R) are true and (R) is the correct explanation of (A)
   2. B.Both (A) and (R) are true but (R) is not the correct explanation of (A)
   3. C.(A) is true but (R) is false
   4. D.(A) is false but (R) is true
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   Answer: A

2. Q502022 · 29 Jul 2022 · Shift 1

   Find the modulation index of an AM wave having $8\mathrm{V}$ variation where maximum amplitude of the AM wave is $9\mathrm{V}$.

   1. A.0.8
   2. B.0.5
   3. C.0.2
   4. D.0.1
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   Answer: A

3. Q572022 · 29 Jul 2022 · Shift 2· Numerical answer
   
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   Answer: 480

4. Q592022 · 29 Jul 2022 · Shift 2· Numerical answer

   A modulating signal $2\sin (6.28\times 10^6)t$ is added to the carrier signal $4\sin (12.56\times 10^9)t$ for amplitude modulation. The combined signal is passed through a non-linear square law device. The output is then passed through a band pass filter. The bandwidth of the output signal of band pass filter will be ____ $\mathrm{MHz}$.

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   Answer: 2

5. Q472022 · 28 Jul 2022 · Shift 1
   
   1. A.
   2. B.
   3. C.
   4. D.
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   Answer: B

6. Q502022 · 28 Jul 2022 · Shift 1

   In the case of amplitude modulation to avoid distortion the modulation index ($\mu$) should be :

   1. A.$\mu \le 1$
   2. B.$\mu \ge 1$
   3. C.$\mu =2$
   4. D.$\mu =0$
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   Answer: A

7. Q492022 · 28 Jul 2022 · Shift 2
   
   1. A.$0.1\text{ V}$
   2. B.$1.0\text{ V}$
   3. C.$10\text{ V}$
   4. D.$100\text{ V}$
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   Answer: B

8. Q502022 · 28 Jul 2022 · Shift 2

   A FM Broadcast transmitter, using modulating signal of frequency 20 kHz has a deviation ratio of 10. The Bandwidth required for transmission is :

   1. A.220 kHz
   2. B.180 kHz
   3. C.360 kHz
   4. D.440 khz
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   Answer: D

9. Q462022 · 27 Jul 2022 · Shift 1
   
   1. A.AND gate
   2. B.OR gate
   3. C.NOR gate
   4. D.NAND gate
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   Answer: A

10. Q452022 · 27 Jul 2022 · Shift 2

    With reference to the observations in photo-electric effect, identify the correct statements from below : (A) The square of maximum velocity of photoelectrons varies linearly with frequency of incident light. (B) The value of saturation current increases on moving the source of light away from the metal surface. (C) The maximum kinetic energy of photo-electrons decreases on decreasing the power of LED (light emitting diode) source of light. (D) The immediate emission of photo-electrons out of metal surface can not be explained by particle nature of light/electromagnetic waves. (E) Existence of threshold wavelength can not be explained by wave nature of light/ electromagnetic waves. Choose the correct answer from the options given below :

    1. A.(A) and (B) only
    2. B.(A) and (E) only
    3. C.(C) and (E) only
    4. D.(D) and (E) only
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    Answer: B

11. Q492022 · 27 Jul 2022 · Shift 2

    For a constant collector-emitter voltage of $8\mathrm{V}$, the collector current of a transistor reached to the value of $6\mathrm{mA}$ from $4\mathrm{mA}$, whereas base current changed from $20\mu \mathrm{A}$ to $25\mu \mathrm{A}$ value. If transistor is in active state, small signal current gain (current amplification factor) will be :

    1. A.240
    2. B.400
    3. C.0.0025
    4. D.200
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    Answer: B

12. Q502022 · 27 Jul 2022 · Shift 2
    
    1. A.0.2
    2. B.0.1
    3. C.0.3
    4. D.0.4
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    Answer: A

13. Q492022 · 26 Jul 2022 · Shift 1

    A radio can tune to any station in $6\mathrm{MHz}$ to $10\mathrm{MHz}$ band. The value of corresponding wavelength bandwidth will be :

    1. A.$4\mathrm{m}$
    2. B.$20\mathrm{m}$
    3. C.$30\mathrm{m}$
    4. D.$50\mathrm{m}$
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    Answer: B

14. Q592022 · 26 Jul 2022 · Shift 1· Numerical answer
    
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    Answer: 9

15. Q482022 · 25 Jul 2022 · Shift 2

    In AM modulation, a signal is modulated on a carrier wave such that maximum and minimum amplitudes are found to be 6 V and 2 V respectively. The modulation index is :

    1. A.100%
    2. B.80%
    3. C.60%
    4. D.50%
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    Answer: D

16. Q502022 · 30 Jun 2022 · Shift 1

    A speech signal given by $11\sin (2200\pi t)\text{ V}$ is used for amplitude modulation with a carrier signal given by $44\sin (6600\pi t)\text{ V}$. The minimum amplitude of modulated wave will be :

    1. A.$33\text{ V}$
    2. B.$55\text{ V}$
    3. C.$8.25\text{ V}$
    4. D.$13.75\text{ V}$
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    Answer: A

17. Q482022 · 28 Jun 2022 · Shift 2
    
    1. A.
    2. B.
    3. C.
    4. D.
    Show answer

    Answer: D

18. Q502022 · 28 Jun 2022 · Shift 2

    Amplitude modulated wave is represented by $V_{AM}=10[1+0.4\cos (2\pi \times 10^{4}t)]\cos (2\pi \times 10^{7}t)$. The total bandwidth of the amplitude modulated wave is :

    1. A.$10\mathrm{kHz}$
    2. B.$20\mathrm{MHz}$
    3. C.$20\mathrm{kHz}$
    4. D.$10\mathrm{MHz}$
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    Answer: C

19. Q482022 · 27 Jun 2022 · Shift 1
    
    1. A.
    2. B.
    3. C.
    4. D.
    Show answer

    Answer: B

20. Q602022 · 27 Jun 2022 · Shift 1· Numerical answer

    The height of a transmitting antenna at the top of a tower is $25\mathrm{m}$ and that of receiving antenna is, $49\mathrm{m}$. The maximum distance between them, for satisfactory communication in LOS (Line-Of-Sight) is $K\sqrt{5}\times 10^2\mathrm{m}$. The value of $K$ is ____. (Assume radius of Earth is $64\times 10^{+5}\mathrm{m}$) [Calculate upto nearest integer value]

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    Answer: 192

21. Q492022 · 27 Jun 2022 · Shift 2

    For a transistor to act as a switch, it must be operated in

    1. A.Active region.
    2. B.Saturation state only.
    3. C.Cut-off state only.
    4. D.Saturation and cut-off state.
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    Answer: D

22. Q502022 · 27 Jun 2022 · Shift 2

    We do not transmit low frequency signal to long distances because- (a) The size of the antenna should be comparable to signal wavelength which is unreal solution for a signal of longer wavelength. (b) Effective power radiated by a long wavelength baseband signal would be high. (c) We want to avoid mixing up signals transmitted by different transmitter simultaneously. (d) Low frequency signal can be sent to long distances by superimposing with a high frequency wave as well. Therefore, the most suitable option will be :

    1. A.All statements are true
    2. B.(a), (b) and (c) are true only
    3. C.(a), (c) and (d) are true only
    4. D.(b), (c) and (d) are true only
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    Answer: C

23. Q602022 · 27 Jun 2022 · Shift 2· Numerical answer
    
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    Answer: 4

24. Q472022 · 26 Jun 2022 · Shift 1
    
    1. A.1 : 2
    2. B.5 : 1
    3. C.1 : 40
    4. D.20 : 1
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    Answer: B

25. Q502022 · 26 Jun 2022 · Shift 1

    Choose the correct statement for amplitude modulation :

    1. A.Amplitude of modulating signal is varied in accordance with the information signal.
    2. B.Amplitude of modulated signal is varied in accordance with the information signal.
    3. C.Amplitude of carrier signal is varied in accordance with the information signal.
    4. D.Amplitude of modulated signal is varied in accordance with the modulating signal.
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    Answer: C