121. The SCR ratings, di/dt in A/μsec and dv/dt in V/μsec, may vary, respectively, between—

1. 1. 20 to 500, 10 to 100

   
   
   

   2. both 20 to 500

   
   
   

   3. both 10 to 100

   
   
   

   4. 50 to 300, 20 to 500

   
   
   

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   NA

   Correct Option: B

   NA

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122. In thyristors—

1. 1. latching current I_L is associated with turn-off process and holding current I_H with turn-on process

   
   
   

   2. both I_L and I_H are associated with turn-off process

   
   
   

   3. I_H is associated with turn-off process and I_L with turn-on process

   
   
   

   4. both I_L and I_H are associated with turn-on process

   
   
   

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   NA

   Correct Option: C

   NA

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123. Once SCR starts conducting a forward current, its gate loses control over—
     

1. 1. anode circuit voltage only

   
   
   

   2. anode circuit current only

   
   
   

   3. anode circuit voltage and current

   
   
   

   4. anode circuit voltage, current and time

   
   
   

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   NA

   Correct Option: C

   NA

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124. On-state voltage drop across a thyristor used in a 250 V supply system is of the order of—

1. 1. 100–110 V

   
   
   

   2. 240–250 V

   
   
   

   3. 1 to 1·5 V

   
   
   

   4. 0·5 to 1 V

   
   
   

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   NA

   Correct Option: C

   NA

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125. In a thyristor, ratio of latching current to holding current is—
     

1. 1. 0·4

   
   
   

   2. 1·0

   
   
   

   3. 2·5

   
   
   

   4. 6·0

   
   
   

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   NA

   Correct Option: C

   NA

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