Thermodynamics MCQs With Answers

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Thermodynamics MCQ 

SET-5

 

81.   The general gas energy equation is (where Q1 – 2 = Heat supplied, dU = Change in internal energy, and W1 – 2 = Work done in heat units)

Answer:  A

82.  The compression ratio for Diesel engines is

  • A.  3 to 6
  • B.  5 to 8
  • C.  15 to 20
  • D.  20 to 30

Answer:  C

83.  In an isothermal process,

  • A.  there is no change in temperature
  • B.  there is no change in enthalpy
  • C.  there is no change in internal energy
  • D.  all of these

Answer:  D


 84.  Which of the following is the correct statement of the second law of thermodynamics?

  • A.  It is impossible to construct an engine working on a cyclic process, whose sole purpose is to convert heat energy into work.
  • B.  It is impossible to transfer heat from a body at a lower temperature to a higher temperature, without the aid of an external source.
  • C.  There is a definite amount of mechanical energy, which can be obtained from a given quantity of heat energy.
  • D.  all of the above

Answer:  D

85.  The heating and expanding of a gas is called thermodynamic system.

  • A.  Yes  
  • B.  No

Answer:  B

86.  Otto cycle efficiency is higher than Diesel cycle efficiency for the same compression ratio and heat input because in Otto cycle

  • A.  combustion is at constant volume
  • B.  expansion and compression are isentropic
  • C.  maximum temperature is higher
  • D.  heat rejection is lower

Answer:  D


87.  Liquid fuels have higher calorific value than solid fuels.

  • A.  Yes  
  • B.  No

Answer:  A


88.  The free expansion process is __________ non-flow process.

  • A.  reversible  
  • B.  irreversible

Answer:  B

89.   A mixture of gas expands from 0.03 m3 to 0.06 m3 at a constant pressure of 1 MPa and absorbs 84 kJ of heat during the process. The change in internal energy of the mixture is

  • A.  30 kJ
  • B.  54 kJ
  • C.  84 kJ
  • D.  114 kJ

90.  The gas constant (R) is equal to the __________ of two specific heats.

  • A.  sum  
  • B.  difference
  • C.  product  
  • D.  ratio

Answer:  B

91.  Hydrogen is the __________ substance.

A.  lightest  

B.  heaviest

Answer:  A


92.  Otto cycle is also known as

  • A.  constant pressure cycle
  • B.  constant volume cycle
  • C.  constant temperature cycle
  • D.  constant temperature and pressure cycle

Answer:  B

93.  For a perfect gas, according to Boyle’s law (where p = Absolute pressure, v = Volume, and T = Absolute temperature)

  • A.  p v = constant, if T is kept constant
  • B.  v/T = constant, if p is kept constant
  • C.  p/T = constant, if v is kept constant
  • D.  T/p = constant, if v is kept constant

Answer:  A


94.  Producer gas is obtained by

  • A.  partial combustion of coal, coke, anthracite coal or charcoal in a mixed air steam blast
  • B.  carbonisation of bituminous coal
  • C.  passing steam over incandescent coke
  • D.  passing air and a large amount of steam over waste coal at about 650°C

Answer:  A


95.  The efficiency of a dual combustion cycle __________ upon cut-off ratio.

  • A.  depends
  • B.  does not depend

Answer:  A


96.  The efficiency of Diesel cycle depends upon

  • A.  temperature limits
  • B.  pressure ratio
  • C.  compression ratio
  • D.  cut-off ratio and compression ratio

Answer:  D

97.  Those substances which have so far not been resolved by any means into other substances of simpler form are called

  • A.  elements  
  • B.  compounds
  • C.  atoms  
  • D.  molecules

Answer:  A


 98.   The measurement of a thermodynamic property known as temperature is based on

  • A.  Zeroth law of thermodynamics
  • B.  First law of thermodynamics
  • C.  Second law of thermodynamics
  • D.  none of these

Answer:  A

99.  Kelvin-Planck’s law deals with

  • A.  conservation of work
  • B.  conservation of heat
  • C.  conversion of heat into work
  • D.  conversion of work into heat

Answer:  C

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