Thermodynamics Important Questions and Answers PDF

1. 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

Answer: Option A

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2. Work done in a free expansion process is

A. Zero

B. Maximum

C. Minimum

D. Positive

Answer: Option A

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3. Work-done in a free expansion process is

A. Zero

B. Minimum

C. Maximum

D. Positive

Answer: Option A

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4. The ratio of root mean square velocity to average velocity of gas molecules at a particular temperature is

A. 0.086

B. 1.086

C. 1.086

D. 4.086

Answer: Option B

5. According to Gay Lussac’s law for a perfect gas, the absolute pressure of given mass varies directly as

A. Temperature

B. Absolute temperature, if volume is kept constant

C. Volume, if temperature is kept constant

D. None of these

Answer: Option B

Thermodynamics Important Questions and Answers PDF

6. The heat and mechanical energies are mutually convertible. This statement was established by

A. Boyle

B. Charles

C. Joule

D. None of these

Answer: Option C

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7. Mond 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: Option D

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8. Producer gas is obtained by

A. Carbonization of bituminous coal

B. Partial combustion of coal, coke, anthracite coal or charcoal in a mixed air steam blast

C. Passing steam over incandescent coke

D. Passing air and a large amount of steam over waste coal at about 650°C

Answer: Option B

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9. In open cycle gas turbine plants

A. Direct combustion systems is used

B. A condenser is used

C. The indirect heat exchanger and cooler is avoided

D. All of the above

Answer: Option D

10. The atomic mass of sulphur is

A. 12

B. 14

C. 16

D. 32

Answer: Option D

Thermodynamics Important Questions and Answers PDF

11. When two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other. This statement is called

A. Zeroth law of thermodynamics

B. First law of thermodynamics

C. Second law of thermodynamics

D. Kelvin Planck's law

Answer: Option A

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12. All perfect gases change in volume by 1/273th of its original volume at 0°C for every 1°C change in temperature, when the pressure remains constant. This statement is called

A. Boyle's law

B. Charle's law

C. Gay-Lussac law

D. Joule's law

Answer: Option B

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13. Which of the following statement is wrong?

A. The closed cycle gas turbine plants are external combustion plants.

B. In the closed cycle gas turbine, the pressure range depends upon the atmospheric pressure.

C. The advantage of efficient internal combustion is eliminated as the closed cycle has an external surface.

D. In open cycle gas turbine, atmosphere acts as a sink and no coolant is required.

Answer: Option B

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14. A process of heating crude oil to a high temperature under a very high pressure to increase the yield of lighter distillates, is known as

A. Cracking

B. Carbonization

C. Fractional distillation

D. Full distillation

Answer: Option A

15. The process is adiabatic, if the value of n in the equation pv^n = C, is

A. Zero

B. One

C. γ

D. ∝

Answer: Option C

Thermodynamics Important Questions and Answers PDF

16. 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

Answer: Option B

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

A. First law of thermodynamics

B. Second law of thermodynamics

C. Zeroth law of thermodynamics

D. None of these

Answer: Option C

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18. Measurement of temperature is based on

A. Thermodynamic properties

B. Zeroth law of thermodynamics

C. First law of thermodynamics

D. Second law of thermodynamics

Answer: Option B

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19. 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

Answer: Option A

20. The absolute zero temperature is taken as

A. 237°C

B. -273°C

C. -237°C

D. 273°C

Answer: Option B

Thermodynamics Important Questions and Answers PDF

21. According to Regnault's law, the specific heat at constant pressure (cp) and specific heat at constant volume (cv) _________ with the change in pressure and temperature of the gas.

A. Change

B. Do not change

C. Both (A) and (B)

D. None of these

Answer: Option B

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22. The natural petroleum may be separated into

A. Petrol

B. Kerosene

C. Fuel oil

D. Lubricating oil

Answer: Option D

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25. For a thermodynamic process to be reversible, the temperature difference between hot body and working substance should be

A. Zero

B. Minimum

C. Maximum

D. Infinity

Answer: Option A

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Thermodynamics Important Questions and Answers PDF

26. Properties of substances like pressure, temperature and density, in thermodynamic coordinates are

A. Path functions

B. Point functions

C. Cyclic functions

D. Real functions

Answer: Option B

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27. Which of the following processes are thermodynamically reversible?

A. Throttling

B. Free expansion

C. Constant volume and constant pressure

D. Isothermal and adiabatic

Answer: Option D

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28. Entropy change depends on

A. Heat transfer

B. Mass transfer

C. Change of temperature

D. Thermodynamic state

Answer: Option A

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29. Coke is produced

A. When coal is strongly heated continuously for 42 to 48 hours in the absence of air in a closed vessel

B. From the finely ground coal by moulding under pressure with or without a binding material

C. When coal is first dried and then crushed to a fine powder by pulverizing machine

D. By heating wood with a limited supply of air to a temperature not less than 280°C

Answer: Option A

30. When a gas is heated at constant pressure

A. Its temperature will increase

B. Its volume will increase

C. Both temperature and volume will increase

D. Neither temperature not volume will increase

Answer: Option C

Thermodynamics Important Questions and Answers PDF

31. The efficiency of Diesel cycle with decrease in cut-off

A. Increases

B. Decreases

C. First increases and then decreases

D. First decreases and then increases

Answer: Option A

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32. Otto cycle consists of

A. Two constant volume and two isentropic processes

B. Two constant pressure and two isentropic processes

C. Two constant volume and two isothermal processes

D. One constant pressure, one constant volume and two isentropic processes

Answer: Option A

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33. Stirling cycle consists of

A. Two constant volume and two isentropic processes

B. Two constant volume and two isothermal processes

C. Two constant pressure and two isothermal processes

D. One constant volume, one constant pressure and two isentropic processes

Answer: Option B

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34. Carnot cycle consists of

A. Two constant volume and two isentropic processes

B. Two isothermal and two isentropic processes

C. Two constant pressure and two isentropic processes

D. One constant volume, one constant pressure and two isentropic processes

Answer: Option B

35. When cut-off ratio is __________ the efficiency of Diesel cycle approaches to Otto cycle efficiency.

A. Zero

B. 1/5

C. 4/5

D. 1

Answer: Option A

Thermodynamics Important Questions and Answers PDF

36. Reversed Joule cycle is known as

A. Carnot cycle

B. Bell-Coleman cycle

C. Rankine cycle

D. Stirling cycle

Answer: Option B

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37. The same volume of all gases would represent their

A. Densities

B. Specific weights

C. Molecular weights

D. Gas characteristic constants

Answer: Option C

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38. If both Stirling and Carnot cycles operate within the same temperature limits, then efficiency of Stirling cycle as compared to

A. More

B. Less

C. Equal

D. Depends on other factors

Answer: Option C

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39. The compression ratio for Diesel engines is

A. 15 to 20

B. 5 to 8

C. 3 to 6

D. 20 to 30

Answer: Option A

Thermodynamics Important Questions and Answers PDF

41. One Joule (J) is equal to

A. 1 kN-m

B. 1 N-m

C. 10 kN-m/s

D. 10 N-m/s

Answer: Option B

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42. Reversed joule cycle is called

A. Carnot cycle

B. Rankine cycle

C. Brayton cycle

D. Bell Coleman cycle

Answer: Option D

Solution:

Apparently, the Brayton cycle and the Joule cycle are almost the same. The reversed Joule cycle is actually known as Bell-coleman cycle. Its purpose is to move heat, rather than produce work.

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43. The entropy __________ in an irreversible cyclic process.

A. Remains constant

B. Decreases

C. Increases

D. None of these

Answer: Option C

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45. The efficiency of Diesel cycle approaches to Otto cycle efficiency when

A. Cut-off is decreased

B. Cut-off is constant

C. Cut-off is increased

D. Cut-off is zero

Answer: Option B

Thermodynamics Important Questions and Answers PDF

46. The heat energy stored in the gas and used for raising the temperature of the gas is known as

A. External energy

B. Internal energy

C. Kinetic energy

D. Molecular energy

Answer: Option B

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47. According to kinetic theory of gases, the velocity of molecules __________ with the increase in temperature.

A. Remains constant

B. Increases

C. Decreases

D. None of these

Answer: Option B

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48. In an isothermal process, the internal energy

A. Increases

B. Decreases

C. Remain constant

D. First increases and then decreases

Answer: Option C

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49. Calorie is a measure of

A. Specific heat

B. Quantity of heat

C. Thermal capacity

D. Entropy

Answer: Option B

50. Kerosene is distilled at

A. 65° to 220°C

B. 220° to 345°C

C. 345° to 470°C

D. 470° to 550°C

Answer: Option B

Thermodynamics Important Questions and Answers PDF

51. For the constant pressure and heat input, the air standard efficiency of gas power cycle is in the order

A. Dual cycle, Diesel cycle, Otto cycle

B. Otto cycle, Diesel cycle, Dual cycle

C. Dual cycle, Otto cycle, Diesel cycle

D. Diesel cycle, Otto cycle, Dual cycle

Answer: Option A

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52. The __________ states that change of internal energy of a perfect gas is directly proportional to the change of temperature.

A. Boyle's law

B. Charle's law

C. Gay-Lussac law

D. Joule's law

Answer: Option D

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53. Select the wrong statement

A. A Joule cycle consists of two constant volume and two isentropic processes.

B. An Otto cycle consists of two constant volume and two isentropic processes.

C. An Ericsson cycle consists of two constant pressure and two isothermal

processes.

D. All of the above

Answer: Option A

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54. The change of entropy, when heat is absorbed by the gas, is

A. Positive

B. Negative

C. Positive or negative

D. None of these

Answer: Option A

55. When gas is heated at constant pressure, the heat supplied is utilized in

A. Increasing the internal energy of gas

B. Doing some external work

C. Increasing the internal energy of gas and also for doing some external work

D. None of the above

Answer: Option C

Thermodynamics Important Questions and Answers PDF

56. Superheated vapour behaves

A. Exactly as gas

B. As steam

C. As ordinary vapour

D. Approximately as a gas

Answer: Option D

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57. Which of the following statement is correct?

A. The heat and work are boundary phenomena

B. The heat and work represent the energy crossing the boundary of the system

C. The heat and work are path functions

D. All of the above

Answer: Option D

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58. Which of the following statement is correct?

A. The increase in entropy is obtained from a given quantity of heat at a low temperature.

B. The change in entropy may be regarded as a measure of the rate of the availability or unavailability of heat for transformation into work.

C. The entropy represents the maximum amount of work obtainable per degree drop in temperature.

D. All of the above

Answer: Option D

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59. The heat flows from a cold body to a hot body with the aid of an external source. This statement is given by

A. Kelvin

B. Joule

C. Clausis

D. Gay-Lussac

Answer: Option C

60. Energy can neither be created nor destroyed, but it can be transformed from one form to another. This statement is known as

A. Zeroth law of thermodynamics

B. First law of thermodynamics

C. Second law of thermodynamics

D. Kinetic theory of gases

Answer: Option B

Thermodynamics Important Questions and Answers PDF

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What is the engineering thermodynamics?

Engineering thermodynamics is the branch of engineering that deals with the study of energy transformations and the relationship between heat and work in various engineering systems. It is concerned with the application of the laws of thermodynamics to the design, analysis, and optimization of thermal systems.

Thermodynamics is the science that deals with the study of energy and its transformations. It is a fundamental science that has many applications in engineering, physics, chemistry, and other fields. The laws of thermodynamics govern the behavior of energy in various systems, including the transfer of heat and work between different components.

Engineering thermodynamics applies these principles to the analysis and design of various engineering systems, such as power plants, engines, refrigeration and air conditioning systems, and chemical processes. It also includes the study of thermodynamic cycles and their efficiencies, as well as the properties of fluids and gases under different conditions.

Overall, engineering thermodynamics plays a crucial role in the design and optimization of energy systems, which are essential for the development and progress of modern society.

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What engineering uses thermodynamics?

Thermodynamics is an important area of study for several branches of engineering. Some of the fields of engineering that heavily rely on thermodynamics include:

Mechanical engineering: Thermodynamics is an integral part of mechanical engineering, which deals with the design, analysis, and manufacturing of mechanical systems. It is used to understand how heat and energy are transferred in mechanical systems, as well as how to optimize the efficiency of these systems.

Chemical engineering: Chemical engineering is concerned with the design, development, and operation of chemical processes and equipment. Thermodynamics plays a critical role in this field, particularly in the design and analysis of chemical reactions and in the development of thermodynamic models for chemical systems.

Aerospace engineering: Aerospace engineers use thermodynamics to design and develop propulsion systems for aircraft and spacecraft. They also use thermodynamics to understand the behavior of fluids at high altitudes and in extreme temperatures.

Electrical engineering: Electrical engineers use thermodynamics to design and optimize power generation and transmission systems. They also use thermodynamics to understand the behavior of materials at high temperatures, which is important for the design of electronic components.

Environmental engineering: Environmental engineers use thermodynamics to design and optimize energy-efficient systems for environmental remediation, pollution control, and waste management. They also use thermodynamics to understand the behavior of pollutants in the environment.

Overall, thermodynamics plays a crucial role in a wide range of engineering disciplines, and engineers in these fields rely on thermodynamic principles to design, analyze, and optimize complex systems.

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What branch of engineering is thermodynamics?

Thermodynamics is a branch of science that deals with the relationships between heat, energy, and work. While it is not a branch of engineering per se, it is an important subject for many fields of engineering, including mechanical engineering, chemical engineering, aerospace engineering, and materials science. In these fields, thermodynamics is used to design and optimize systems such as engines, power plants, chemical reactors, and materials processing equipment.

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Thermodynamics Important Questions and Answers PDF