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Top 100 MCQ Engineering Thermodynamics

Subject ⇒Engineering Thermodynamics

1. Which of the following variables controls the physical properties of a perfect gas
(a) pressure
(b) temperature
(c) volume
(d) all of the above
Ans: d
2. Which of the following laws is applicable for the behavior of a perfect gas
(a) Boyle’s law
(b) Charles’law
(c) Gay-Lussac law
(d) all of the above
Ans: d
3. The unit of temperature in S.I. units is
(a) Centigrade
(b) Celsius
(c) Fahrenheit
(d) Kelvin
Ans: d
4. The unit of mass in S.I. units is
(a) kilogram
(b) gram
(c) tonne
(d) quintal
Ans: a
5. The unit of time in S.I. units is
(a) second
(b) minute
(c) hour
(d) day
Ans: a
6. The unit of length in S.I. units is
(a) meter
(b) centimeter
(c) kilomete
(d) millimeter.
Ans: a
7. The unit of energy in S.I. units is
(a) watt
(b) joule
(c) joule/s
(d) joule/m
Ans: b
8. According to Gay-Lussac law for a perfect gas, the absolute pressure of given mass varies directly as
(a) temperature
(b) absolute
(c) absolute temperature, if volume is kept constant
(d) volume, if temperature is kept constant
Ans: c
9. An ideal gas as compared to a real gas at very high pressure occupies
(a) more volume
(b) less volume
(c) same volume
(d) unpredictable behaviour
(e) no such correlation.
Ans: a
10. General gas equation is
(a) PV=nRT
(b) PV=mRT
(d) PV = C
(c) PV=KiRT
(e) Cp-Cv = Wj
Ans: b
11. According to Dalton’s law, the total pres sure of the mixture of gases is equal to
(a) greater of the partial pressures of all
(b) average of the partial pressures of all
(c) sum of the partial pressures of all
(d) sum of the partial pressures of all divided by average molecular weight
(e) atmospheric pressure.
Ans: c
12. Which of the following can be regarded as gas so that gas laws could be applicable, within the commonly encountered temperature limits.
(a) 02, N2, steam, C02
(b) Oz, N2, water vapour
(c) S02, NH3, C02, moisture
(d) 02, N2, H2, air
Ans: d
13. The unit of pressure in S.I. units is
(a) kg/cm2
(b) mm of water column
(c) pascal
(d) dynes per square cm
Ans: c
14. A closed system is one in which
(a) mass does not cross boundaries of the system, though energy may do so
(b) mass crosses the boundary but not the energy
(c) neither mass nor energy crosses the boundaries of the system
(d) both energy and mass cross the boundaries of the system
Ans: a
15. Temperature of a gas is produced due to
(a) its heating value
(b) kinetic energy of molecules
(c) repulsion of molecules
(d) attraction of molecules
Ans: b
16. According to kinetic theory of gases, the absolute zero temperature is attained when
(a) volume of the gas is zero
(b) pressure of the gas is zero
(c) kinetic energy of the molecules is zero
(d) specific heat of gas is zero
Ans: c
17. Kinetic theory of gases assumes that the collisions between the molecules are
(a) perfectly elastic
(b) perfectly inelastic
(c) partly elastic
(d) partly inelastic
Ans: a
18. Diesel cycle consists of following four processes
(a) two isothermals and two isentropics
(b) two isentropics, and two constant volumes.
(c) two isentropics, one constant volume and one constant pressure
(d) two isentropics and two constant pressures
Ans: c
Ans: d
19. Kinetic energy of the molecules in terms of absolute temperature (T) is proportional to
(a) T
(b) j
(c) J2
(d) Vr
Ans: a
20. Superheated vapour behaves
(a) exactly as gas
(b) as steam
(c) as ordinary vapour
(d) approximately as a gas
Ans: d
21. Absolute zero pressure will occur
(a) at sea level
(b) at the center of the earth
(c) when molecular momentum of the system becomes zero
(d) under vacuum conditions
Ans: c
22. No liquid can exist as liquid at
(a) – 273 °K
(b) vacuum
(c) zero pressure
(d) centre of earth
Ans: c
23. The unit of power in S.I. units is
(a) newton
(b) pascal
(c) erg
(d) watt
Ans: d
24. The condition of perfect vacuum, i.e., absolute zero pressure can be attained at
(a) a temperature of – 273.16°C
(b) a temperature of 0°C
(c) a temperature of 273 °K
(d) a negative pressure and 0°C temperature
Ans: a
25. Intensive property of a system is one whose value
(a) depends on the mass of the system, like volume
(b) does not depend on the mass of the system, like temperature, pressure, etc.
(c) is not dependent on the path followed but on the state
(d) is dependent on the path followed and not on the state
Ans: b
26. Specific heat of air at constant pressure is equal to
(a) 0.17
(b) 0.21
(c) 0.24
(d) 1.0
Ans: c
27. Characteristic gas constant of a gas is equal to
(a) C/Cv
(b) Cv/Cp
(c) Cp – Cv
(d) Cp + Cv
Ans: c
28. The behaviour of gases can be fully determined by
(a) 1 law
(b) 2 laws
(c) 3 laws
(d) 4 laws
Ans: d
29. The ratio of two specific heats of air is equal to
(a) 0.17
(b) 0.24
(c) 0.1
(d) 1.41
Ans: d
30. Boyle’s law i.e. pV = constant is applicable to gases under
(a) all ranges of pressures
(b) only small range of pressures
(c) high range of pressures
(d) steady change of pressures
Ans: b
31. Which law states that the internal energy of a gas is a function of temperature
(a) Charles’ law
(b) Joule’s law
(c) Regnault’s law
(d) Boyle’s law
Ans: b
32. The same volume of all gases would represent their
(a) densities
(b) specific weights
(c) molecular weights
(d) gas characteristic constants
Ans: c
33. Which law states that the specific heat of a gas remains constant at all temperatures and pressures
(a) Charles’ Law
(b) Joule’s Law
(c) Regnault’s Law
(d) Boyle’s Law
Ans: c
34. An open system is one in which
(a) mass does not cross boundaries of the system, though energy may do so
(b) neither mass nor energy crosses the boundaries of the system
(c) both energy and mass cross the boundaries of the system
(d) mass crosses the boundary but not the energy
Ans: c
35. According to which law, all perfect gases change in volume by l/273th of their original volume at 0°C for every 1°C change in temperature when pressure remains constant
(a) Joule’s law
(b) Boyle’s law
(c) Regnault’s law
(d) Gay-Lussac law
(e) Charles’ law.
Ans: e
36. Gases have
(a) only one value of specific heat
(b) two values of specific heat
(c) three values of specific heat
(d) no value of specific heat
Ans: b
37. According to Avogadro’s Hypothesis
(a) the molecular weights of all the perfect gases occupy the same volume under same conditions of pressure and temperature
(b) the sum of partial pressure of mixture of two gases is sum of the two
(c) product of the gas constant and the molecular weight of an ideal gas is constant
(d) gases have two values of specific heat
Ans: a
38. Extensive property of a system is one whose value
(a) depends on the mass of the system like volume
(b) does not depend on the mass of the system, like temperature, pressure, etc.
(c) is not dependent on the path followed but on the state
(d) is dependent on the path followed and not on the state
Ans: a
39. Work done in a free expansion process is
(a) + ve
(b) -ve
(c) zero
(d) maximum
Ans: c
40. The statement that molecular weights of all gases occupy the same volume is known as
(a) Avogadro’s hypothesis
(b) Dalton’s law
(c) Gas law
(d) Law of thermodynamics
Ans: a
41. To convert volumetric analysis to gravimetric analysis, the relative volume of each constituent of the flue gases is
(a) divided by its molecular weight
(b) multiplied by its molecular weight
(c) multiplied by its density
(d) multiplied by its specific weight
Ans: b
42. If a gas is heated against a pressure, keeping the volume constant, then work done will be equal to
(a) + v
(b) – ve
(c) zero
(d) pressure x volume
Ans: c
43. An isolated system is one in which
(a) mass does not cross boundaries of the system, though energy may do so
(b) neither mass nor energy crosses the boundaries of the system
(c) both energy and mass cross the boundaries of the system
(d) mass crosses the boundary but not the energy
Ans: b
44. Properties of substances like pressure, temperature and density, in thermodynamic coordinates are
(a) path functions
(b) point functions
(c) cyclic functions
(d) real functions
Ans: b
45. Which of the following quantities is not the property of the system
(a) pressure
(b) temperature
(c) specific volume
(d) heat
(e) density
Ans: d
46. According to Avogadro’s law, for a given pressure and temperature, each molecule of a gas
(a) occupies volume proportional to its molecular weight
(b) occupies volume proportional to its specific weight
(c) occupies volume inversely proportional to its molecular weight
(d) occupies volume inversely proportional to its specific weight
(e) occupies same volume.
Ans: e
47. Mixture of ice and water form a
(a) closed system
(b) open system
(c) isolated system
(d) heterogeneous system
Ans: d
48. Which of the following is the property of a system
(a) pressure and temperature
(b) internal energy
(c) volume and density
(d) enthalpy and entropy
(e) all of the above.
Ans: e
49. On weight basis, air contains following parts of oxygen
(a) 21
(b) 23
(c) 25
(d) 73
Ans: b
50. Which of the following is not the intensive property
(a) pressure
(b) temperature
(c) density
(d) heat
Ans: d
51. Which of the following items is not a path function
(a) heat
(b) work
(c) kinetic energy
(d) vdp
(e) thermal conductivity.
Ans: e
52. Work done in an adiabatic process between a given pair of end states depends on
(a) the end states only
(b) particular adiabatic process
(c) the value of index n
(d) the value of heattransferred
Ans: a
53. Heat and work are
(a) point functions
(b) system properties
(c) path functions
(d) intensive properties
Ans: c
54. Which of the following parameters is constant for a mole for most of the gases at a given temperature and pressure
(a) enthalpy
(b) volume
(c) mass
(d) entropy
Ans: b
55. The value of n = 1 in the polytropic process indicates it to be
(a) reversible process
(b) isothermal process
(c) adiabatic process
(d) irreversible process
Ans: b
56. Solids and liquids have
(a) one value of specific heat
(b) two values of specific heat
(c) three values of specific heat
(d) no value of specific heat
Ans: a
57. A perfect gas at 27°C is heated at constant pressure till its volume is double. The final temperature is
(a) 54°C
(b) 327°C
(c) 108°C
(d) 654°C
Ans: b
58. Curve A in Fig. 1.1 compared to curves B and C shows the following type of expansion
(a) pV”=C
(b) isothermal
(c) adiabatic
(d) free expansion
Ans: b
59. If value of n is infinitely large in a polytropic process pV” = C, then the process is known as constant
(a) volume
(b) pressure
(c) temperature
(d) enthalpy
Ans: a
60. The index of compression n tends to reach ratio of specific heats y when
(a) flow is uniform and steady
(b) process is isentropic
(c) process is isothermal
(d) process is isentropic and specific heat does not change with temperature
Ans: d
61. Change in enthalpy of a system is the heat supplied at
(a) constant pressure
(b) constant temperature
(c) constant volume
(d) constant entropy
Ans: a
62. The term N.T.P. stands for
(a) nominal temperature and pressure
(b) natural temperature and pressure
(c) normal temperature and pressure
(d) normal thermodynamic practice

Ans: c
63. A heat exchange process in which the product of pressure and volume remains constant is known as
(a) heat exchange process
(b) throttling process
(c) isentropic process
(d) adiabatic process
(e) hyperbolic process.
Ans: e
64. In an isothermal process, the internal energy of gas molecules
(a) increases
(b) decreases
(c) remains constant
(d) may increase/decrease depending on the properties of gas
Ans: c
65. Zeroth law of thermodynamics
(a) deals with conversion of mass and energy
(b) deals with reversibility and irreversibility of process
(c) states that if two systems are both in equilibrium with a third system, they are in thermal equilibrium with each other
(d) deals with heat engines
Ans: c
66. If a certain amount of dry ice is mixed with same amount of water at 80°C, the final temperature of mixture will be
(a) 80°C
(b) 0°C
(c) 40°C
(d) 20°C
Ans: b
67. The basis for measuring thermodynamic property of temperature is given by
(a) zeroth law of thermodynamics
(b) first law of thermodynamics
(c) second law of thermodynamics
(d) third law of thermodynamics
Ans: a
68. One watt is equal to
(a) 1 Nm/s
(b) 1 N/mt
(c) 1 Nm/hr
(d) 1 kNm/hr
Ans: a
69. Work done is zero for the following process
(a) constant volume
(b) free expansion
(c) throttling
(d) all Of the above
Ans: d
70. For which of the following substances, the gas laws can be used with minimum error
(a) dry steam
(b) wet steam
(c) saturated steam
(d) superheated steam
Ans: d
71. In a non-flow reversible process for which p = (- 3V+ 15) x 105N/m2,V changes from 1 m to 2 m3. The work done will be about
(a) 100 xlOO5 joules
(b) lxlO5 joules
(c) 10 xlO5 joules
(d) 10 xlO5 kilo joules
Ans: c
72. The value of the product of molecular weight and the gas characteristic constant for all the gases in M.K.S. unit is
(a) 29.27 kgfm/mol°K
(b) 8314kgfm/mol°K
(c) 848kgfm/mol°K
(d) 427kgfm/mol°K
Ans: c
73. On volume basis, air contains following parts of oxygen
(a) 21
(b) 23
(c) 25
(d) 77
Ans: a
74. Universal gas constant is defined as equal to product of the molecular weight of the gas and
(a) specific heat at constant pressure
(b) specific heat at constant volume
(c) ratio of two specific heats
(d) gas constant
Ans: d
75. The value of the product of molecular weight and the gas characteristic constant for all the gases in S.I. units is
(a) 29.27 J/kmol°K
(b) 83.14J/kmol°K
(c) 848J/kmol°K
(d) All J/kmol °K
Ans: b
76. For which of the following substances, the internal energy and enthalpy are the functions of temperature only
(a) any gas
(b) saturated steam
(c) water
(d) perfect gas
Ans: d
77. In a free expansion process
(a) work done is zero
(b) heat transfer is zero
(c) both
(a) and
(b) above
(d) work done is zero but heat increases
Ans: c
78. If a gas vapour is allowed to expand through a very minute aperture, then such a process is known as
(a) free expansion
(b) hyperbolic expansion
(c) adiabatic expansion
(d) parabolic expansion
(e) throttling.
Ans: e
79. The specific heat of air increases with increase in
(a) temperature
(b) pressure
(c) both pressure and temperature
(d) variation of its constituents
Ans: a
80. If a fluid expands suddenly into vacuum through an orifice of large dimension, then such a process is called
(a) free expansion
(b) hyperbolic expansion
(c) adiabatic expansion
(d) parabolic expansion
Ans: a
81. Which of the following processes are thermodynamically reversible
(a) throttling
(b) free expansion
(c) constant volume and constant pressure
(d) hyperbolic and pV = C
(e) isothermal and adiabatic.
Ans: e
82. Which of the following processes is irreversible process
(a) isothermal
(b) adiabatic
(c) throttling
(d) all of the above
Ans: c
83. In order that a cycle be reversible, following must be satisfied
(a) free expansion or friction resisted expansion/compression process should not be encountered
(b) when heat is being absorbed, temperature of hot source and working sub¬stance should be same
(c) when beat is being rejected, temperature of cold source and working sub-stance should be same
(d) all of the above
Ans: d
84. For a thermodynamic process to be reversible, the temperature difference between hot body and working substance should be
(a) zero
(b) minimum
(d) maximum
(d) infinity
Ans: a
85. Minimum work in compressor is possible when the value of adiabatic index n is equal to
(a) 0.75
(b) 1
(c) 1.27
(d) 1.35
Ans: b
86. Molecular volume of any perfect gas at 600 x 103 N/m2 and 27°C will be
(a) 4.17m3/kgmol
(b) 400 m3/kg mol
(c) 0.15 m3/kg mol
(d) 41.7 m3/kg mol
Ans: a
87. A gas is compressed in a cylinder by a movable piston to a volume one-half its original volume. During the process 300 kJ heat left the gas and internal energy remained same. The work done on gas in Nm will be
(a) 300 Nm
(b) 300,000 Nm
(c) 30 Nm
(d) 3000 Nm
Ans: b
88. The more effective way of increasing efficiency of Carnot engine is to
(a) increase higher temperature
(b) decrease higher temperature
(c) increase lower temperature
(d) decrease lower temperature
Ans: d
89. Entropy change depends on
(a) heat transfer
(b) mass transfer
(c) change of temperature
(d) thermodynamic state
Ans: a
90. For reversible adiabatic process, change in entropy is
(a) maximum
(b) minimum
(c) zero
(d) unpredictable
Ans: c
91. Isochoric process is one in which
(a) free expansion takes place
(b) very little mechanical work is done by the system
(c) no mechanical work is done by the system
(d) all parameters remain constant
Ans: c
92. According to first law of thermodynamics
(a) work done by a system is equal to heat transferred by the system
(b) total internal energy of a system during a process remains constant
(c) internal energy, enthalpy and entropy during a process remain constant
(d) total energy of a system remains constant
Ans: d
93. Energy can neither be created nor destroyed but can be converted from one form to other is inferred from
(a) zeroth low of thermodynamic
(b) first law of thermodynamics
(c) second law to thermodynamics
(d) basic law of thermodynamics
Ans: b
94. First law of thermodynamics furnishes the relationship between
(a) heat and work
(b) heat, work and properties of the system
(c) various properties of the system
(d) various thermodynamic processes
Ans: b
95. Change in enthalpy in a closed system is equal to heat transferred if the reversible process takes place at constant
(a) pressure
(b) temperature
(c) volume
(d) internal energy
Ans: a
96. In an isothermal process, the internal energy
(a) increases
(b) decreases
(c) remains constant
(d) first increases and then decreases
Ans: c
97. Change in internal energy in a closed system is equal to heat transferred if the reversible process takes place at constant
(a) pressure
(b) temperature
(c) volume
(d) internal energy
Ans: c
98. According to first law of thermodynamics
(a) mass and energy are mutually convertible
(b) Carnot engine is most efficient
(c) heat and work are mutually convertible
(d) mass and light are mutually convertible
Ans: c
99. Total heat of a substance is also known as
(a) internal energy
(b) entropy
(c) thermal capacity
(d) enthalpy
Ans: d
100. First law of thermodynamics
(a) enables to determine change in internal energy of the system
(b) does not help to predict whether the system will or not undergo a change
(c) does not enable to determine change in entropy
(d) provides relationship between heat, work and internal energy
(e) all of the above.
Ans: e

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