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