Semiconductors & Communication · JEE Main previous year questions

2021 29 questions

1. Q542021 · 26 Feb 2021 · Shift 2· Numerical answer
   
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   Answer: 9

2. Q602021 · 26 Feb 2021 · Shift 2· Numerical answer

   If the highest frequency modulating a carrier is 5 kHz, then the number of AM broadcast stations accommodated in a 90 kHz bandwidth are _________.

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   Answer: 9

3. Q462021 · 25 Feb 2021 · Shift 2

   For extrinsic semiconductors; when doping level is increased;

   1. A.Fermi-level of both p-type and n-type semiconductors will go upward for $T>T_F\text{K}$ and downward for $T<T_F\text{K}$, where $T_F$ is Fermi temperature.
   2. B.Fermi-level of p-type semiconductor will go upward and Fermi-level of n-type semiconductors will go downward
   3. C.Fermi-level of p and n-type semiconductors will not be affected.
   4. D.Fermi-level of p-type semiconductors will go downward and Fermi-level of n-type semiconductor will go upward.
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   Answer: D

4. Q502021 · 25 Feb 2021 · Shift 2

   If a message signal of frequency '$f_m$' is amplitude modulated with a carrier signal of frequency '$f_c$' and radiated through an antenna, the wavelength of the corresponding signal in air is :

   1. A.$\frac{c}{f_c+f_m}$
   2. B.$\frac{c}{f_c}$
   3. C.$\frac{c}{f_c-f_m}$
   4. D.$\frac{c}{f_m}$
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   Answer: B