1. What is the fundamental property that defines the thermodynamic state of a system?
a) Temperature
b) Pressure
c) Volume
d) Entropy
Answer: a) Temperature
Explanation: Temperature is a fundamental property that determines the thermal equilibrium between two systems. It defines the direction of heat transfer and is crucial in determining the state of a system in thermodynamics.
2. Which law of thermodynamics states that energy cannot be created or destroyed, only transformed from one form to another?
a) Zeroth law
b) First law
c) Second law
d) Third law
Answer: b) First law
Explanation: The first law of thermodynamics, also known as the law of conservation of energy, states that the total energy of an isolated system remains constant. It forms the basis for understanding energy conservation in various thermodynamic processes.
3. Which of the following is a steady flow process?
a) Charging a battery
b) Boiling water in an open vessel
c) Heating a closed container of gas
d) Operating a turbine
Answer: d) Operating a turbine
Explanation: A steady flow process involves the continuous flow of mass or energy through a system without any change in the system’s properties with respect to time. Operating a turbine is an example of such a process where there is a continuous flow of fluid through the turbine.
4. What is the primary limitation of the first law of thermodynamics?
a) It does not account for changes in entropy
b) It only applies to reversible processes
c) It cannot predict the direction of spontaneous processes
d) It does not consider the internal energy of a system
Answer: c) It cannot predict the direction of spontaneous processes
Explanation: The first law of thermodynamics states that energy is conserved in any process, but it does not provide information about the direction of a spontaneous process, which is crucial in understanding the natural flow of energy.
5. Which law of thermodynamics introduces the concept of entropy?
a) Zeroth law
b) First law
c) Second law
d) Third law
Answer: c) Second law
Explanation: The second law of thermodynamics introduces the concept of entropy, which is a measure of the disorder or randomness of a system. It states that in any natural process, the total entropy of a closed system tends to increase over time.
6. Which thermodynamic cycle represents the maximum theoretical efficiency for a heat engine operating between two temperature reservoirs?
a) Carnot cycle
b) Brayton cycle
c) Rankine cycle
d) Otto cycle
Answer: a) Carnot cycle
Explanation: The Carnot cycle is a theoretical thermodynamic cycle that represents the most efficient heat engine possible operating between two temperature reservoirs. It consists of reversible isothermal and adiabatic processes.
7. Which statement best describes Clausius’ inequality?
a) Heat flows spontaneously from a hot object to a cold object
b) The entropy of a closed system always increases
c) No process is possible whose sole result is the transfer of heat from a cooler to a hotter object
d) The efficiency of all real heat engines is less than that of a Carnot engine
Answer: b) The entropy of a closed system always increases
Explanation: Clausius’ inequality states that the entropy of an isolated system never decreases and tends to increase over time in natural processes. It is a consequence of the second law of thermodynamics.
8. What property of a system is represented by the area under a T-S diagram?
a) Entropy
b) Enthalpy
c) Temperature
d) Internal energy
Answer: a) Entropy
Explanation: In a T-S (Temperature-Entropy) diagram, the area under the curve represents the entropy change of a system during a process. It provides insight into the heat transfer and irreversible processes occurring within the system.
9. Which device operates on the reversed Carnot cycle to transfer heat from a low-temperature reservoir to a high-temperature reservoir?
a) Heat engine
b) Heat pump
c) Refrigerator
d) Turbine
Answer: b) Heat pump
Explanation: A heat pump is a device that uses mechanical work to transfer heat from a low-temperature reservoir to a high-temperature reservoir, operating on the reversed Carnot cycle.
10. What concept in thermodynamics refers to the maximum useful work that can be obtained from a system at a given state?
a) Available energy
b) Unavailable energy
c) Internal energy
d) Enthalpy
Answer: a) Available energy
Explanation: Available energy, also known as exergy, represents the maximum useful work that can be obtained from a system when it reaches equilibrium with its surroundings. It is a measure of the quality of energy within a system.
11. Which law of thermodynamics establishes the basis for the concept of thermal equilibrium?
a) Zeroth law
b) First law
c) Second law
d) Third law
Answer: a) Zeroth law
Explanation: The Zeroth law of thermodynamics states that if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. This law establishes the concept of temperature and provides a foundation for defining the thermal equilibrium of systems.
12. Which term refers to the measure of the disorder or randomness of a system?
a) Temperature
b) Enthalpy
c) Entropy
d) Internal energy
Answer: c) Entropy
Explanation: Entropy is a thermodynamic property that quantifies the amount of disorder or randomness in a system. It increases in the direction of natural processes and is closely related to the second law of thermodynamics.
13. In which process does the total entropy of a closed system remain constant?
a) Isobaric process
b) Isochoric process
c) Adiabatic process
d) Reversible process
Answer: d) Reversible process
Explanation: In a reversible process, the total entropy of a closed system remains constant. Reversible processes are idealized processes that can be reversed without leaving any trace on the surroundings or system.
14. What does the Clausius Inequality state regarding the direction of heat transfer?
a) Heat cannot be transferred from a colder object to a hotter object spontaneously
b) Heat transfer is always from a hotter object to a colder object spontaneously
c) Heat transfer is independent of the temperature difference between two objects
d) Heat transfer is reversible between any two objects
Answer: a) Heat cannot be transferred from a colder object to a hotter object spontaneously
Explanation: Clausius’ inequality states that it is impossible for heat to transfer from a colder object to a hotter object spontaneously without external work being applied to the system. This is a direct consequence of the second law of thermodynamics.
15. Which thermodynamic process involves no change in volume?
a) Isobaric process
b) Isochoric process
c) Isothermal process
d) Adiabatic process
Answer: b) Isochoric process
Explanation: An isochoric process, also known as a constant volume process, involves no change in volume. It typically occurs in a closed container where the system is thermally insulated, allowing only heat transfer without work being done on or by the system.
16. Which type of engine operates most efficiently between two temperature reservoirs?
a) Diesel engine
b) Otto engine
c) Carnot engine
d) Stirling engine
Answer: c) Carnot engine
Explanation: The Carnot engine operates most efficiently between two temperature reservoirs according to Carnot’s theorem. It is an idealized engine that achieves maximum efficiency based on reversible processes.
17. What is the primary purpose of a heat pump?
a) To generate electricity
b) To transfer heat from a cold space to a hot space
c) To cool a space by absorbing heat
d) To convert thermal energy into mechanical work
Answer: b) To transfer heat from a cold space to a hot space
Explanation: A heat pump is designed to transfer heat from a colder space to a hotter space, typically for heating purposes. It operates by using mechanical work to move thermal energy against the natural direction of heat flow.
18. Which property of a substance remains constant during an adiabatic process?
a) Temperature
b) Pressure
c) Volume
d) Internal energy
Answer: d) Internal energy
Explanation: In an adiabatic process, no heat is transferred into or out of the system, so the change in internal energy is solely due to work done on or by the system. Therefore, the internal energy remains constant during such a process.
19. What concept in thermodynamics refers to the maximum amount of useful work that can be obtained from a system?
a) Exergy
b) Enthalpy
c) Entropy
d) Irreversibility
Answer: a) Exergy
Explanation: Exergy, also known as available energy, is the maximum useful work that can be obtained from a system when it reaches equilibrium with its surroundings. It represents the quality of energy within a system and is a key concept in thermodynamic analysis.
20. Which law of thermodynamics establishes the relationship between the change in internal energy and heat transfer and work done on or by a system?
a) Zeroth law
b) First law
c) Second law
d) Third law
Answer: b) First law
Explanation: The first law of thermodynamics, also known as the law of conservation of energy, relates the change in internal energy of a system to the heat transfer into or out of the system and the work done on or by the system. It forms the basis for energy conservation in thermodynamic processes.