16. A Carnot cycle is having an efficiency of 0.75. If the temperature of the high temperature reservoir is 727°C. What is the temperature of low temperature reservoir?

1. 1. 23°C

   
   
   

   2. –23°C

   
   
   

   3. 0°C

   
   
   

   4. 250°C

   
   
   

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1. View Hint View Answer Discuss in Forum

   1 -	T2	= 0.75
   	T1

   
   

   T2	= 0.25
   273 - 727

   
   T₂ = 0.25K
   T₂ = 727 – 250
   [T₂ – 23°C]

   Correct Option: B

   1 -	T2	= 0.75
   	T1

   
   

   T2	= 0.25
   273 - 727

   
   T₂ = 0.25K
   T₂ = 727 – 250
   [T₂ – 23°C]

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17. The slopes of constant volume and constant pressure lines in the T-s diagram are _______ and _________ respectively.

1. 1. 	ds	=	CP
      	dt		T

   
   
   

   2. 	dt	=	CP
      	ds		T

   
   
   

   3. 	ds	+	CP
      	dt		T

   
   
   

   4. 	ds	+	T
      	dt		CP

   
   
   

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1. View Hint View Answer Discuss in Forum

   Tds = du + pdv
   Constant volume
   Tds = dv (dv = 0)
   Tds = C_Vdt
   

   	dt	=	CV		.......(i)
   	ds		T

   
   Tds = du – vdp
   Constant pressure
   

   	dt	=	CP		....(ii)
   	ds		T

   Correct Option: B

   Tds = du + pdv
   Constant volume
   Tds = dv (dv = 0)
   Tds = C_Vdt
   

   	dt	=	CV		.......(i)
   	ds		T

   
   Tds = du – vdp
   Constant pressure
   

   	dt	=	CP		....(ii)
   	ds		T

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18. A 1500 W electrical heater is used to heat 20 kg of water (cp = 4186 J/kgK) in an insulated bucket, from a temperature of 30°C to 80°C. If the heater temperature is only infinitesimally larger than the water temperature during the process, the change in entropy for the heater is _________ J/K and for water J/K.

1. 1. 12786.99 J/kg

   
   
   

   2. 22786.99 J/kg

   
   
   

   3. 1200.99 J/kg

   
   
   

   4. – 12786.99 J/kg

   
   
   

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1. View Hint View Answer Discuss in Forum

   ds = mCIn	Th
   	Ti

   
   

   (20)(4186) In	353
   	303

   
   ds_water = 12786.99 J/kg
   ds_rod = – 12786.99 J/kg

   Correct Option: D

   ds = mCIn	Th
   	Ti

   
   

   (20)(4186) In	353
   	303

   
   ds_water = 12786.99 J/kg
   ds_rod = – 12786.99 J/kg

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19. If a closed system is undergoing an irreversible process, the entropy of the system

1. 1. must increase

   
   
   

   2. always remains constant

   
   
   

   3. must decrease

   
   
   

   4. can increase, decrease or remain constant

   
   
   

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1. View Hint View Answer Discuss in Forum

   (ds)_uni ≥ 0

   Correct Option: A

   (ds)_uni ≥ 0

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20. One kilogram of water at room temperature is brought into contact with a high temperature thermal reservoir. The entropy change of the universe is

1. 1. equal to entropy change of the reservoir

   
   
   

   2. equal to entropy change of water

   
   
   

   3. equal to zero

   
   
   

   4. always positive

   
   
   

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1. View Hint View Answer Discuss in Forum

   

   Correct Option: D

   

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