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Basic Concepts & Zeroth Law of Thermodynamics 5

81. The density of water is maximum at 
 (a) 20 ÂºC             (b) 4 ºC
 (c) 0 ÂºC               (d) -4 ÂºC 
UPPSC AE 12.04.2016 Paper-II 
Ans : (b) The maximum density of water occurs at 4  ÂºC because, at this temperature two opposing effects are in balance. In ice, the water molecules are in a crystal lattice that has a lot of empty space. When the ice melts to liquid water, the structure collapses and the density of the liquid increases. Thus, the density of water is a maximum at 4 ºC
                             

 82. A perfect gas at 27 °C is heated at constant pressure so as to triple its volume. The final temperature of the gas will be.
 (a) 81 °C             (b) 270°C
 (c) 627 °C           (d) 900°C
 RPSC INSP. OF FACTORIES AND BOILER 2016
 TSPSC AEE 2015
Ans : (c) 

83. A non-flow device compresses air isothermally at a temperature of 500oC from a pressure of 5.0 MPa to a final pressure of 15.0 MPa. If the device uses 200 kJ/kg of work input, then this process is
 (a) impossible 
 (b) irreversible 
 (c) either reversible or irreversible 
 (d) reversible 
BHEL ET 2019 
Ans. (a) 

 84. The net work done per kg of gas in a polytropic process is equal to
 UKPSC AE 2007 Paper -II

85. Which of the following is not a property of system? 
 (a) Temperature             (b) Pressure
 (c) Specific volume        (d) Heat
 UKPSC AE 2007 Paper -II 
 Ans. (d) : Heat

 86. Which cycle has maximum efficiency for the same temperature limits?
 (a) Brayton             (b) Carnot 
 (c) Rankine             (d) Stirling 
UKPSC AE 2007 Paper -II 
 Ans. (b) : Carnot 

87. The work done is constant volume process is
 (a) maximum             (b) minimum 
 (c) zero                     (d) unpredictable
 UKPSC AE 2007 Paper -II 
 Ans. (c) : Zero 

88. In a reversible adiabatic process heat added is equal to 
 (a) zero             (b) positive value
 UKPSC AE 2007 Paper -II 
 Ans. (a) : Zero 

89. In an irreversible process there is a 
 (a) loss of heat             (b) no loss of heat 
(c) gain of heat             (d) no gain of heat
 UKPSC AE 2012, 2007 Paper–II
 Ans. (a) : loss of heat

90. Choose the correct alternative: 
 1. First law for a closed system undergoing a cycle Q – W = ∆E 
 2. Two reversible adiabatic paths can not intersect each other.
 3. If two fluids are mixed, the entropy of universe remains unchanged. 
 4. Clausius statement – Heat can flow from low to high temperature body without the aid of external work. 
 5. The efficiency of a reversible heat engine is independent of nature of working substance undergoing a cycle.
 (a) All statements are true. 
 (b) Statements 2 and 5 are true. 
 (c) Statements 1, 3, 4 and 5 are true. 
 (d) Statements 1, 3 and 5 are true. 
UKPSC AE 2012 Paper–II 
Ans. (b) : Statements 2 and 5 are true. 

91. The unit of work is
 (a) kW                 (b) kWh 
 (c) kW/h              (d) kJ/s
 UKPSC AE 2012 Paper–II 
Ans. (b) : kWh 

92. A system is taken from state A to state B along two different paths 1 and 2. The heat absorbed and work done by the system along these paths are Q1 and Q2 and W1 and W2 respectively, then 
 (a) Q1 = Q2             (b) W1 + Q1 = Q2 + W2 
 (c) W1 = W2           (d) Q1 – W1 = Q2 – W2
 UKPSC AE 2012 Paper–II 
Ans. (d) : Q1 – W1 = Q2 – W2 

93. Which of the following is an irreversible process ? 
 (a) An isothermal process
 (b) An isentropic process 
 (c) An isobaric process 
 (d) An isenthalpic process 
UKPSC AE 2012 Paper–II 
Ans. (d) : An isenthalpic process 

94. The work in a closed system undergoing an isentropic process is given by 
 
 (Notations used have usual meaning) 
UKPSC AE 2012 Paper–II 
Ans. (c)   

95. The thermal efficiency of a theoretical Otto cycle
 (a) increases with increase in compression ratio
 (b) increases with increase in isentropic index γ 
 (c) does not depend on the pressure ratio 
 (d) follows all the above 
UKPSC AE 2012 Paper–II 
Ans. (d) : follows all the above 

96. T1 is high and T2 is low temperature of a Carnot heat engine. Which is the most efficient way to increase efficiency? 
 (a) To increase T1 
 (b) To decrease T2 
 (c) To increase T1 and T2 both
 (d) To decrease T1 and T2 both 
UKPSC AE-2013, Paper-II 
Ans. (b) :

 97. For non-flow closed system the value of net energy transferred as heat and work equals change in:- 
 (a) Enthalpy              (b) Entropy 
 (c) Internal energy     (d) None of the above 
UKPSC AE-2013, Paper-II 
Ans. (c) :

 98. Pick the correct statement regarding path function. 
 (a) The differentials of point functions are inexact differentials 
 (b) The differentials of point functions & path functions are exact differentials. 
 (c) The differentials of path function are inexact differentials. 
 (d) The differentials of path functions are exact differentials. 
BHEL ET 2019 
Ans. (c) : • The differential of path functions are inexact differentials where as differential of point functions are exact differentials. 

99. The pressure inside a balloon is proportional to the square of its diameter. It contains 2 kg of water at 150 kPa with 85% quality. The balloon and water are now heated so that a final pressure of 600 kPa is reached. the process undergone by the water is given by p-v equation as :
 
BHEL ET 2019
 Ans. (a) 

100. A gas goes through a process given by . = It expands from state 1 of 350 kPa and 0.049 m 3 to a final pressure of 150 KPa. Work delivered during this process in kJ is : 
 (a) 4.765         (b) 8.5 
 (c) 5.915         (d) 3.897 
BHEL ET 2019
 Ans. (c)

 101. When the valve of an evacuated bottle is opened, the atmospheric air rushes into it. If the atmospheric pressure is 101.325 kPa and 0.6 m3 of air enters into the bottle, then the work done by the air will be
 (a) 80.8 kJ         (b) 70.8 kJ 
 (c) 60.8 kJ         (d) 50.8 kJ 
ESE 2018 
Ans. (c)

102. For the quick response of a thermocouple 
 (a) Its wire diameter should be large 
 (b) The convective heat transfer coefficient should be high 
 (c) The specific heat should be high
 (d) The density should not be very small 
UPPSC AE 12.04.2016 Paper-II 
Ans : (b) For the quick response of a thermocouple the convective heat transfer coefficient should be high.

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