96. A balloon containing an ideal gas is initially kept in an evacuated and insulated room. The balloon ruptures and the gas fills up the entire room. Which one of the following statements is TRUE at the end of above process?
    

1. 1. The internal energy of the gas decreases from its initial value, but the enthalpy remains constant.
      

   
   
   

   2. The internal energy of the gas increases from its initial value, but the enthalpy remains constant.
      

   
   
   

   3. Both internal energy and enthalpy of the gas remain constant
      

   
   
   

   4. Both internal energy and enthalpy of the gas increase

   
   
   

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1. View Hint View Answer Discuss in Forum

   Since the kinetic energy of the molecules won’t
   change in vacuum ⇒ temperature remains constant ⇒ internal energy remains constant.
   

   Now ,	PV	= constant
   	T

   
   ⇒ PV = constant
   ⇒ H = U + PV = constant

   Correct Option: C

   Since the kinetic energy of the molecules won’t
   change in vacuum ⇒ temperature remains constant ⇒ internal energy remains constant.
   

   Now ,	PV	= constant
   	T

   
   ⇒ PV = constant
   ⇒ H = U + PV = constant

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97. If the specific heats of the working fluid are constant and the value of specific heat ratio γ is 1.4, the thermal efficiency (%) of the cycle is

1. 1. 21
      

   
   
   

   2. 40.9
      

   
   
   

   3. 42.6
      

   
   
   

   4. 59.7

   
   
   

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1. View Hint View Answer Discuss in Forum

   21

   Correct Option: A

   21

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98. The above cycle is represented on T-s plane by
    

1. 1. 
      

   
   
   

   2. 
      

   
   
   

   3. 
      

   
   
   

   4. 

   
   
   

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1. View Hint View Answer Discuss in Forum

   Since 3 – 1 is adiabatic process, it will be represented by a straight line on T – s plane. 1 – 2 is isobaric process, so with decreases of volume, temperature will also decrease.

   Correct Option: C

   Since 3 – 1 is adiabatic process, it will be represented by a straight line on T – s plane. 1 – 2 is isobaric process, so with decreases of volume, temperature will also decrease.

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99. A reversible thermodynamic cycle containing only three processes and producing work is to be constructed. The constraints are:
    (i) there must be one isothermal process,
    (ii) there must be one isentropic process,
    (iii) the maximum and minimum cycle pressures and the clearance volume are fixed, and
    (iv) polytropic processes are not allowed. Then the number of possible cycles are
    

1. 1. 1
      

   
   
   

   2. 2
      

   
   
   

   3. 3
      

   
   
   

   4. 4

   
   
   

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1. View Hint View Answer Discuss in Forum

   1

   Correct Option: A

   1

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100. The following four figures have been drawn to represent a fictitious thermodynamic cycle, on the P-v and T-s planes.
     
     According to the first law of thermodynamics, equal areas are enclosed by
     

1. 1. Figures 1 and 2
      

   
   
   

   2. Figures 1 and 3
      

   
   
   

   3. Figures 1 and 4
      

   
   
   

   4. Figures 2 and 3

   
   
   

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1. View Hint View Answer Discuss in Forum

   Figures 1 and 2

   Correct Option: A

   Figures 1 and 2

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