216. An incandescent lamp is marked 40W, 240V. If resistance at room temperature (26°C) is 120 Ω and temperature coefficient of resistance is 4.5 × 10^{– 3/°C} , then its ‘ON ’ state filament temperature in °C is approximately ___________.
     

1. 1. 1171

   
   
   

   2. 2471

   
   
   

   3. 1417

   
   
   

   4. All of the above

   
   
   

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1. View Hint View Answer Discuss in Forum

   P = 40 W
   V = 240V
   

   Now , Rlamp =	V2	=	2402	= 1440 Ω
   	P		40

   
   AT t = 26 °, R = 120W and α = 4.5 × 10^{– 3}/ °C
   Now R_lamp = R[1 + α (t₂ – t₁)]
   ∴ 1440 = 120[ 1 + 4.5 × 10^{– 3} (θ₂ - 26)]
   t₂ = 2470.44 °C

   Correct Option: B

   P = 40 W
   V = 240V
   

   Now , Rlamp =	V2	=	2402	= 1440 Ω
   	P		40

   
   AT t = 26 °, R = 120W and α = 4.5 × 10^{– 3}/ °C
   Now R_lamp = R[1 + α (t₂ – t₁)]
   ∴ 1440 = 120[ 1 + 4.5 × 10^{– 3} (θ₂ - 26)]
   t₂ = 2470.44 °C

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217. In the figure, the value of resistor R is (25 + I/2) ohms, where I is the current in amperes. The current I is _________
     

1. 1. 15

   
   
   

   2. 5

   
   
   

   3. 10

   
   
   

   4. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   R =		25 +	I
   			2

   
   Now V = RI
   

   ∴ 300 = I		25 +	I			∴ R = 25 +	I
   			2				2

   
   ∴ 600 = 50 I + I²
   I = 10 A or – 60 A
   I² + 50 I – 600 = 0
   ∴ I = 10A
   

   Correct Option: C

   R =		25 +	I
   			2

   
   Now V = RI
   

   ∴ 300 = I		25 +	I			∴ R = 25 +	I
   			2				2

   
   ∴ 600 = 50 I + I²
   I = 10 A or – 60 A
   I² + 50 I – 600 = 0
   ∴ I = 10A
   

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218. Two identical coupled inductors are connected in series. The measured inductances for the two possible series connections are 380 H and 240 H. Their mutual inductance in μH is _____

1. 1. 35 to 35

   
   
   

   2. 36

   
   
   

   3. 35

   
   
   

   4. 30 to 35

   
   
   

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1. View Hint View Answer Discuss in Forum

   
   

   Correct Option: A

   
   

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219. The total power dissipated in the circuit, shown in the figure, is 1 kW.
     
     The voltmeter, across the load, reads 200 V. The value of X_L is ___________.

1. 1. 11.43

   
   
   

   2. 17.3

   
   
   

   3. 117.3 to 17.4

   
   
   

   4. 17.3 to 17.4

   
   
   

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1. View Hint View Answer Discuss in Forum

   Power dissipation = 1 kW = 1000 W
   ⇒ 1000 = 2² .1 + 10². R
   [Power dissipation occurs in 1 Ω and Resistor R]
   ⇒ 1000 = 4 + 100 R
   ⇒ R = 9.96 Ω
   Now ,
   ⇒ 200² = 100 R² + 100 X_L²
   ⇒ 10X_L = 173.43
   ⇒ X_L = 17.34
   

   Correct Option: D

   Power dissipation = 1 kW = 1000 W
   ⇒ 1000 = 2² .1 + 10². R
   [Power dissipation occurs in 1 Ω and Resistor R]
   ⇒ 1000 = 4 + 100 R
   ⇒ R = 9.96 Ω
   Now ,
   ⇒ 200² = 100 R² + 100 X_L²
   ⇒ 10X_L = 173.43
   ⇒ X_L = 17.34
   

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220. The Norton’s equivalent source in amperes as seen into the terminals X and Y is _______.
     
     

1. 1. 1

   
   
   

   2. 2

   
   
   

   3. 3

   
   
   

   4. 4

   
   
   

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1. View Hint View Answer Discuss in Forum

   
   

   ISC(IN) =	5	⇒ ISC = 1 A
   	5

   
   [Answer is not matching]
   

   Correct Option: B

   
   

   ISC(IN) =	5	⇒ ISC = 1 A
   	5

   
   [Answer is not matching]
   

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