21. The circuit in Fig. shows zener-regulated dc power supply. The zener diode is ideal. The minimum value of R_L down to which the output voltage remains constant is—
    
    
    

1. 1. 27 Ω

   
   
   

   2. 45 Ω

   
   
   

   3. 15 Ω

   
   
   

   4. 24 Ω
      

   
   
   

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   NA

   Correct Option: B

   NA

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22. For a symmetrical square wave of 800 V peak to peak and for ideal diode, the voltmeter in Fig. will read—
    
    
    
    
    

1. 1. 200 V

   
   
   

   2. 400 V

   
   
   

   3. 800 V

   
   
   

   4. zero

   
   
   

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   NA

   Correct Option: A

   NA

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23. During forward blocking state, a thyristor is associated with—

1. 1. large current, low voltage

   
   
   

   2. low current, large voltage

   
   
   

   3. medium current, large voltage

   
   
   

   4. low current, medium voltage
      

   
   
   

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   NA

   Correct Option: B

   NA

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24. The peak current through the resistor of circuit of Fig. assuming the diodes to be ideal, is—
    
    
    

1. 1. 12 mA

   
   
   

   2. 4 mA

   
   
   

   3. 16 mA

   
   
   

   4. 8 mA

   
   
   

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   NA

   Correct Option: D

   NA

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25. A voltage v = 4 sin ωt is applied to the terminals A and B of the circuit shown in Fig. The diodes are assumed to be ideal. The impedance offered by the circuit across the terminals A and B in kilo-ohms is—
    
    
    

1. 1. 5

   
   
   

   2. 20

   
   
   

   3. 10

   
   
   

   4. None of these

   
   
   

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   NA

   Correct Option: C

   NA

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