Free Thermodynamics MCQs with Answers
714 Thermodynamics MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Thermal equilibrium and heat explain how temperature and energy transfer are related, while molar specific heats describe the heat required by a gas at constant volume or constant pressure. The first law connects heat supplied, work done and change in internal energy, with sign conventions kept distinct from temperature changes.
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Read the Thermodynamics notesFree MDCAT chapter notes with key terms714 questions · page 31 of 36
- A. Increases.
- B. Decreases.
- C. Remains constant.
- D. Varies unpredictably.
Explanation: In an isothermal process, the temperature of the system remains constant.
Correct answer: Remains constant.- A. I only.
- B. III only.
- C. II or III.
- D. I or III.
Explanation: In a Carnot cycle, the working substance undergoes a series of processes that eventually return it to its initial state, which implies the…
Correct answer: I or III.- A. Sink only.
- B. Source only.
- C. Surrounding.
- D. Source and sink.
Explanation: The efficiency of a Carnot engine is determined by the temperatures of both the heat source (T1) and the heat sink (T2).
Correct answer: Source and sink.- A. Adiabatic expansion
- B. Isothermal expansion
- C. Adiabatic compression
- D. Isothermal compression
Explanation: The correct answer is Adiabatic expansion. In this process, the system does work on the surroundings without any heat exchange, leading to…
Correct answer: Adiabatic expansion- A. Depends on the path taken to reach a state
- B. Independent of the path taken to reach a state
- C. Always increasing in a closed system
- D. Dependent only on external factors
Explanation: In thermodynamics, internal energy is a state function, meaning it is determined by the state of the system and is independent of the path…
Correct answer: Independent of the path taken to reach a state- A. Increases
- B. Decreases
- C. Remains the same
- D. Varies unpredictably
Explanation: The efficiency of a Carnot engine is calculated using the formula: efficiency = 1 - (T_sink / T_source), where T_sink and T_source are the…
Correct answer: Decreases- A. Decrease in energy in the system.
- B. Increase in energy in the surrounding.
- C. Unavailability of energy in the system.
- D. Degradation of energy in the environment.
Explanation: Entropy is a concept from thermodynamics often described as a measure of disorder or randomness.
Correct answer: Unavailability of energy in the system.- A. equal to 0 K.
- B. less than 0 K.
- C. equal to its input temperature.
- D. less than its input temperature.
Explanation: To achieve 100% efficiency, a heat engine would require its output temperature (cold reservoir temperature) to be at absolute zero (0 K).
Correct answer: equal to 0 K.- A. 8.4%.
- B. 15.3%.
- C. 18.3%.
- D. 84.5%.
Explanation: The efficiency of a turbine in a thermal power plant can be calculated using the Carnot efficiency formula, which is the maximum…
Correct answer: 15.3%.- A. mass of active substance.
- B. volume of active substance.
- C. pressure on the hot reservoir.
- D. temperature of hot and cold reservoirs.
Explanation: The efficiency of a Carnot cycle, which is a theoretical thermodynamic cycle, is solely dependent on the absolute temperatures of the hot…
Correct answer: mass of active substance.- A. Adiabatic compression isothermal expansion isobaric compression isochoric expansion
- B. Isothermal expansion isobaric compression adiabatic compression isochoric expansion
- C. Isothermal expansion adiabatic expansion isothermal compression adiabatic compression
- D. Isobaric compression isothermal expansion isochoric expansion adiabatic compression
Explanation: 1. Isothermal expansion: Heat is absorbed at a constant high temperature (\(T_{H}\)) while the system expands and does work. 2.
Correct answer: Isothermal expansion adiabatic expansion isothermal compression adiabatic compression- A. 25 %
- B. 50 %
- C. 60 %
- D. 65 %
Explanation: Efficiency (η) = 1 - (T_cold / T_hot)Where: * T_hot = Temperature of the fire chamber (hot reservoir) = 1500 K * T_cold = Temperature of…
Correct answer: 60 %- A. i to ii
- B. ii to iii
- C. iii to iv
- D. iv to v
Explanation: 1. Understanding Work Done in a P-V Graph: In a Pressure-Volume (P-V) graph, the work done by or on a gas during a process is represented…
Correct answer: ii to iii- A. Be halved.
- B. Be doubled.
- C. Remain constant.
- D. Vary unpredictably.
Explanation: The specific heat of a gas, defined as the amount of heat required to change the temperature of a unit mass of the gas by one degree, is a…
Correct answer: Remain constant.- A. 200 J/kgoC.
- B. 100 J/kgoC.
- C. 22.2 J/kgoC.
- D. 11.7 J/kgoC.
Explanation: Q = mcΔTWhere: * Q = Thermal energy transferred (in Joules, J) * m = Mass of the substance (in kilograms, kg) * c = Specific heat capacity…
Correct answer: 200 J/kgoC.- A. Cp = Cv + R/M
- B. Cp = R/Cv
- C. Cp = γ * R
- D. Cp = Cv * M
Explanation: To find the specific heat at constant pressure per gram of a gas with molar mass M, we start with the fundamental thermodynamic relations…
Correct answer: Cp = Cv + R/M617. By reducing the absolute temperature of a black body to half, the total energy radiated will be:
- A. 4
- B. 16
- C. 1/4
- D. 1/16
Explanation: The total energy radiated by a black body is governed by the Stefan-Boltzmann law.
Correct answer: 1/16- A. Flow of heat.
- B. Applied force.
- C. Applied pressure.
- D. Flow of internal energy.
Explanation: The second law of thermodynamics is fundamentally about the direction of processes.
Correct answer: Flow of heat.- A. Remains unchanged.
- B. Becomes half the original.
- C. Becomes twice the original.
- D. Becomes thrice the original.
Explanation: In an ideal gas, the average translational kinetic energy of the molecules is directly proportional to the absolute temperature of the…
Correct answer: Becomes half the original.- A. The same temperature and the same nature of working substance.
- B. Different temperature and the same nature of working substance.
- C. The same temperature irrespective of the nature of working substance.
- D. Different temperatures irrespective of the nature of working substance.
Explanation: The efficiency of a Carnot engine is determined by the temperature difference between the hot and cold reservoirs.
Correct answer: The same temperature irrespective of the nature of working substance.