21. n-type of semiconductor is

1. 1. Negatively charged

   
   
   

   2. Positively charged

   
   
   

   3. Neutral

   
   
   

   4. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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22. Consider the following statements
    1. In a semiconductor, the uppermost band is the valence band
    2. All semiconductors are electrically neutral
    3. With increase of temperature the resistivity of semiconductor decreases
    4. Addition of a small amount of impurity of a III or V group elements to a pure semiconductor increases its resistivity
    Choose the correct statements

1. 1. 1 and 2

   
   
   

   2. 2 and 3

   
   
   

   3. 3 and 4

   
   
   

   4. 1 and 4

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

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23. In a p-type semiconductor,

1. 1. Holes are the only carriers

   
   
   

   2. Electrons are the only carriers

   
   
   

   3. Holes are the majority carriers and electrons are the minority carriers

   
   
   

   4. None of the above

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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24. What does the term Dolby B or Dolby C printed on tape recorders and other sound systems refer to ?

1. 1. Frequency modulated system

   
   
   

   2. Amplitude modulated system

   
   
   

   3. Nose reduction circuit

   
   
   

   4. Both DC and AC power can be used

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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25. In black and white televisions, pictures on the screen are produced due to bombardment of

1. 1. X - ray photons on a white screen

   
   
   

   2. X - ray photons on a white fluorescent screen

   
   
   

   3. Electrons on a white screen

   
   
   

   4. Electrons on a fluorescent white screen

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   NA

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