56. In the circuit shown in the figure, the maximum current in the main SCR can be (given I₀ = 70.7) ______ A .
    

1. 1. 170.7

   
   
   

   2. 70.7

   
   
   

   3. 170

   
   
   

   4. 107.7

   
   
   

---

1. View Hint View Answer Discuss in Forum

   IPeak = Io + Vs

   = 70.7 + 200

   
   = 170.7 A

   Correct Option: A

   IPeak = Io + Vs

   = 70.7 + 200

   
   = 170.7 A

---

57. The circuit in the figure shows zener regulated dc power supply. The zener diode is ideal. The minimum value of RL down to which the output voltage remain constant, is ______ Ω .
    

1. 1. 15

   
   
   

   2. -45

   
   
   

   3. 45

   
   
   

   4. 90

   
   
   

---

1. View Hint View Answer Discuss in Forum

   I =	24 - 15	=	1	A ; and VL = 15 V
   	27		3

   
   

   ∴ RL =	VL	=	15	= 45 Ω
   	I		1 / 3

   Correct Option: C

   I =	24 - 15	=	1	A ; and VL = 15 V
   	27		3

   
   

   ∴ RL =	VL	=	15	= 45 Ω
   	I		1 / 3

---

---

58. A dc source of 100 V supplies a purely inductive load 0.1 H. The controller is a thyristor in series with the source and load. The latching current specified is 100 mA. The minimum width of the gating pulse to ensure thyristor turn ON is ______ s .
    

1. 1. 100

   
   
   

   2. 200

   
   
   

   3. 500

   
   
   

   4. 1000

   
   
   

---

1. View Hint View Answer Discuss in Forum

   For an inductive load,
   

   V = L	di	=	LI
   	dt		T

   
   

   ⇒ T =	LI	=	0.1 × 100 × 10-3	= 0.1 ms or 100 μs
   	V		100

   
   

   Correct Option: A

   For an inductive load,
   

   V = L	di	=	LI
   	dt		T

   
   

   ⇒ T =	LI	=	0.1 × 100 × 10-3	= 0.1 ms or 100 μs
   	V		100

   
   

---

59. If in a 3-phase, half-wave rectifier, if per phase input voltage is 200 V, then average output voltage is ______ V.

1. 1. 233.91

   
   
   

   2. 33.91

   
   
   

   3. 333.91

   
   
   

   4. None of the above

   
   
   

---

1. View Hint View Answer Discuss in Forum

   Since V_t = 200 V, therefore
   table>V_o =

   3 √2 V_ph = 3 √2 × 200 = 233.91 Vπ3.1414

   Correct Option: A

   Since V_t = 200 V, therefore
   table>V_o =

   3 √2 V_ph = 3 √2 × 200 = 233.91 Vπ3.1414

---

---

60. In the circuit shown below what is the output voltage (V_out) in Volts if a silicon transistor Q and an ideal op-amp are used?
    
    

1. 1. – 15

   
   
   

   2. – 0.7

   
   
   

   3. + 0.7

   
   
   

   4. +15

   
   
   

---

1. View Hint View Answer Discuss in Forum

   
   I = I, e I = I₀e ^{V_RE / V_T} , I = I₀e ^{-V₀ / V_T}
   

   -V0 = VT		ln	I		= VT ln		I3ms
   			I0				Is

   
   V₀ = - 0.7
   R_L = √R_s² + X_s² = √4² + 3² = 5

   Correct Option: B

   
   I = I, e I = I₀e ^{V_RE / V_T} , I = I₀e ^{-V₀ / V_T}
   

   -V0 = VT		ln	I		= VT ln		I3ms
   			I0				Is

   
   V₀ = - 0.7
   R_L = √R_s² + X_s² = √4² + 3² = 5

---