491. The forbidden energy gap in semiconductors—

1. 1. Lies just below the valence band.

   
   
   

   2. Lies just above the conduction band.

   
   
   

   3. Lies between the valence band and the conduction band

   
   
   

   4. Is the same as the valence band.
      

   
   
   

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   The forbidden energy gap in semiconductors lies between the valence band and the conduction band.

   Correct Option: C

   The forbidden energy gap in semiconductors lies between the valence band and the conduction band.

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492. The conduction band—

1. 1. Is always located at the top of the crystal.

   
   
   

   2. Is also called the forbidden energy gap.

   
   
   

   3. Is a range of energies corresponding to the free electrons.

   
   
   

   4. Is not an allowed energy band.

   
   
   

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1. View Hint View Answer Discuss in Forum

   The conduction band is a range of energies corresponding to the free electrons.

   Correct Option: C

   The conduction band is a range of energies corresponding to the free electrons.

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493. Donor type impurities—

1. 1. Create excess holes.

   
   
   

   2. Can be added to germanium, but not to silicon.

   
   
   

   3. Must have only three valence electrons.

   
   
   

   4. Must have only five valence electrons.
      

   
   
   

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   NA

   Correct Option: D

   NA

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494. If a small amount of antimony is added to germanium—

1. 1. The resistance is increased.

   
   
   

   2. The germanium will be a p-type semiconductor.

   
   
   

   3. The antimony becomes an acceptor impurity.

   
   
   

   4. There will be more free electrons than holes in the semiconductor.

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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495. The movement of a hole is brought about by—

1. 1. The vacancy being filled by a free electron.

   
   
   

   2. The vacancy being filled by a valence electron from a neighbouring atom.

   
   
   

   3. The movement of an atomic core.

   
   
   

   4. The atomic core changing from a + 4 to a + 5 charge.
      

   
   
   

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1. View Hint View Answer Discuss in Forum

   The movement of hole is brought about by the vacancy being filled by a valence electron from a neighbouring atom. Because hole is nothing but a vacancy creater by electron movement.
   

   Correct Option: B

   The movement of hole is brought about by the vacancy being filled by a valence electron from a neighbouring atom. Because hole is nothing but a vacancy creater by electron movement.
   

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