146. In the figure, switch S is closed at t = 0 with i_L (0) = 0 and V_C (0) = 0. In steady state V_C equals ______ .
     

1. 1. 0

   
   
   

   2. 1

   
   
   

   3. 2

   
   
   

   4. None of the above

   
   
   

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1. View Hint View Answer Discuss in Forum

   At t = 0, i_L (0) = 0, V_C(0) = 0
   ∴ V_D = 100 V
   But at steady-state inductor is short circuited, therefore
   V_C = 100 – (+100) = 0 V
   

   Correct Option: A

   At t = 0, i_L (0) = 0, V_C(0) = 0
   ∴ V_D = 100 V
   But at steady-state inductor is short circuited, therefore
   V_C = 100 – (+100) = 0 V
   

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147. An SCR can withstand a maximum junction temperature of 120°C with an ambient temperature of 75°C. If the SCR has thermal resistance from junction to ambient as 1.5°C / W, the maximum internal power dissipation allowed is ______W .
     

1. 1. 1

   
   
   

   2. 6

   
   
   

   3. 15

   
   
   

   4. 30

   
   
   

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1. View Hint View Answer Discuss in Forum

   Pmax =	TJ - TA	=	120 - 75	= 30 W
   	θjA		1.5

   Correct Option: D

   Pmax =	TJ - TA	=	120 - 75	= 30 W
   	θjA		1.5

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148. For an UJT employed for the triggering of an SCR, stand-off ratio h = 0.64 and dc source voltage V_BB is 20 V. The UJT would trigger when the emitter voltage is ______V.

1. 1. 4.1

   
   
   

   2. 13.1

   
   
   

   3. 51

   
   
   

   4. 3.1

   
   
   

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1. View Hint View Answer Discuss in Forum

   E_BB = V_T + hV_BB = 0.3 + 0.64 × 20 = 13.1 V

   Correct Option: B

   E_BB = V_T + hV_BB = 0.3 + 0.64 × 20 = 13.1 V

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149. A thyristor is triggered by a pulse train of 5 kHz. The duty ratio is 0.4. If allowable average power is 100 W, then maximum allowable gate drive power is ______W .

1. 1. 250

   
   
   

   2. 50

   
   
   

   3. 150

   
   
   

   4. 450

   
   
   

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1. View Hint View Answer Discuss in Forum

   Pmax ≥	Pav
   	f Ton

   
   

   Duty cycle , δ =	Ton	= fTon
   	T

   
   

   ∴ Pmax ≥	Pav	=	100	= 250 W
   	δ		0.4

   Correct Option: A

   Pmax ≥	Pav
   	f Ton

   
   

   Duty cycle , δ =	Ton	= fTon
   	T

   
   

   ∴ Pmax ≥	Pav	=	100	= 250 W
   	δ		0.4

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150. The latching current of SCR is 18 mA. Its holding current will be ______ mA .

1. 1. 3

   
   
   

   2. 6

   
   
   

   3. 7

   
   
   

   4. 21

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: B

   NA

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