Free First Law of Thermodynamics MCQs with Answers
297 First Law of 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.
The first law relates heat supplied, work done and the change in internal energy through energy conservation. Problems use sign conventions and apply the law to isothermal, adiabatic, isobaric and isochoric processes. Internal energy is a state function, while heat and work depend on the path followed.
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297 questions · page 2 of 15
- A. reversible isothermal processes
- B. reversible adiabatic processes
- C. reversible processes during which no work is done
- D. reversible isobaric processes
Explanation: During a reversible isothermal process, where the temperature remains constant, and the process is carried out reversibly, the change in…
Correct answer: reversible isothermal processes- A. rapid escape of air from a burst tyre
- B. rapid expansion of air
- C. cloud formation in the atmosphere
- D. conversion of water into ice in refrigerator
Explanation: When water turns into ice in a refrigerator, heat is typically removed from the water to lower its temperature.
Correct answer: conversion of water into ice in refrigerator- A. 40K, 20K
- B. 100K, 80K
- C. 20K, 30K
- D. 60K,40K
Explanation: The efficiency of a Carnot engine is determined by the temperature difference between the hot and cold reservoirs.
Correct answer: 40K, 20K- A. 10%
- B. 20%
- C. 25%
- D. 44%
Explanation: The efficiency of a Carnot engine is determined by the temperature difference between the hot and cold reservoirs.
Correct answer: 20%- A. work
- B. energy
- C. heat
- D. All of these
Explanation: The first law of thermodynamics is a consequence of the conservation of energy, which states that energy cannot be created or destroyed…
Correct answer: All of these- A. Increases
- B. Decreases
- C. Remains the same
- D. Cannot be predicted
Explanation: At constant pressure (isobaric process), the graph between volume (V) and temperature (T) is typically a straight line.
Correct answer: Remains the same- A. Mass
- B. Heat
- C. Energy
- D. All
Explanation: The first law of thermodynamics states that energy cannot be created or destroyed in an isolated system. It can only change forms.
Correct answer: Energy- A. Isobaric
- B. Adiabatic
- C. Isothermal
- D. Isochoric
Explanation: An adiabatic process is one in which no heat enters or leaves the system.
Correct answer: Adiabatic- A. Increases
- B. Decreases
- C. Zero
- D. Remains constant
Explanation: In the Carnot cycle, the internal energy of the working substance remains constant throughout the cycle.
Correct answer: Remains constant- A. W=−Δ(U)
- B. Entropy of system remains the same
- C. Δ(Q)=0
- D. All of these
Explanation: In an adiabatic process, no heat exchange (Δ(Q)=0) occurs between the system and its surroundings (Q=0).
Correct answer: All of these- A. Decreases
- B. Increases
- C. Remains the same
- D. 0
Explanation: During adiabatic expansion, the system performs work on its surroundings without exchanging heat.
Correct answer: Decreases- A. Temperature
- B. Internal energy
- C. Heat
- D. Pressure
Explanation: Heat (Q) is not a state function. It depends on the path taken during a process, whereas state functions like temperature, internal…
Correct answer: Heat- A. P(V2 −V1 )
- B. P(V1 −V2 )
- C. P(V1^γ −V2^γ )
- D. P(1/V1 −1/V2 )
Explanation: The work done by a gas under constant pressure P) during expansion or compression is given by P×(change in volume).
Correct answer: P(V2 −V1 )- A. Volume
- B. Temperature
- C. Pressure
- D. Path followed
Explanation: According to the ideal gas law, the internal energy of an ideal gas depends only on its temperature.
Correct answer: Temperature- A. 100 J
- B. -100 J
- C. 200 J
- D. 1/100 J
Explanation: For an adiabatic process, the change in internal energy (ΔU) is related to the work done (W) by the equation ΔU=−W.
Correct answer: -100 J- A. Isothermal change
- B. Adiabatic change
- C. Isobaric change.
- D. Isochoric change
Explanation: The Laplace formula is related to the adiabatic process in thermodynamics.
Correct answer: Adiabatic change- A. Isobaric process
- B. Adiabatic process
- C. Isothermal process
- D. Isochoric process
Explanation: An isochoric process is a thermodynamic process that occurs at constant volume.
Correct answer: Isochoric process- A. First law of thermodynamics
- B. Second law of thermodynamics
- C. Newton's laws of motion
- D. Entropy
Explanation: A refrigerator operates on the principles of the second law of thermodynamics.
Correct answer: Second law of thermodynamics- A. There will be a change in internal energy
- B. There will be a change in temperature
- C. There will be no change in internal energy
- D. The external pressure will increase
Explanation: This describes a free expansion process into a vacuum. Since no external pressure is overcome, the work done (W) is zero.
Correct answer: There will be no change in internal energy- A. Increased by 80 joules
- B. Decreased by 80 joules
- C. Increased by 20 joules
- D. Decreased by 20 joules
Explanation: Using the first law of thermodynamics, ΔU = Q - W. Here, heat flows in, so Q = +30 J, and the system does work, so W = +50 J.
Correct answer: Decreased by 20 joules