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
(e) superheated steam
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
(e) work done is zero but heat decreases
Ans: c
78. If a gas vapor 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
(e) air flow
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
(e) throttling
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
(e) none 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
(e) none 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
(e) there is no such criterion
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
(e) 2
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
(e) 417m3/kgmol
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
(e) 30,000 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
(e) keep lower temperature constant
Ans: d
89. Entropy change depends on
(a) heat transfer
(b) mass transfer
(c) change of temperature
(d) thermodynamic state
(e) change of pressure and volume
Ans: a
90. For reversible adiabatic process, change in entropy is
(a) maximum
(b) minimum
(c) zero
(d) unpredictable
(e) negative
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
(e) mass and energy transfer do not take place
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
(e) entropy 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
(e) claussius statement
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
(e) heat and internal energy
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
(e) entropy
Ans: a
96. In an isothermal process, the internal energy
(a) increases
(b) decreases
(c) remains constant
(d) first increases and then decreases
(e) first decreases and then increases
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
(e) entropy
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
(e) heat flows from hot substance to cold substance
Ans: c
99. Total heat of a substance is also known as
(a) internal energy
(b) entropy
(c) thermal capacity
(d) enthalpy
(e) thermal conductance
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