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 9 of 15
- A. decrease
- B. increase
- C. become zero
- D. remain constant
Explanation: During an isothermal process, the temperature of the system remains constant.
Correct answer: remain constant- A. Work can never be converted into heat.
- B. Work can be converted completely into heat.
- C. Both heat and work are interconvertible.
- D. Heat can never be converted into work.
- E. Heat can be converted completely into work.
Explanation: Yes, heat and work are interconvertible forms of energy. In thermodynamics, they can be transformed into each other.
Correct answer: Both heat and work are interconvertible.- A. Isochoric
- B. Isobaric
- C. Adiabatic
- D. Isotropic
- E. Isothermal
Explanation: The process in which all the supplied heat is converted into work is called a reversible isothermal process.
Correct answer: Isothermal- A. Remains constant during the initial phase of the process
- B. Remains constant throughout the process
- C. Alters throughout the process
- D. Increases throughout the process
Explanation: In an isothermal process, the temperature of the system remains constant.
Correct answer: Remains constant throughout the process- A. 1
- B. 0
- C. -1
- D. 2
Explanation: In an adiabatic process, the value of heat energy (\(Q\)) is zero. This is because, by definition, an adiabatic process is one in which no…
Correct answer: 0- A. Adiabatic condition
- B. Isobaric condition
- C. Isochoric condition
- D. Isothermal condition
Explanation: The isothermal condition is the best for performing maximum work, particularly in reversible processes, because the system can exchange…
Correct answer: Isothermal condition- A. becomes maximum
- B. becomes minimum
- C. becomes zero
- D. remains constant
Explanation: In an isothermal process change in energy ΔU becomes zero.
Correct answer: becomes zero- A. Adiabatic condition
- B. Isochoric condition
- C. Isobaric condition
- D. Isothermal condition
Explanation: In an isochoric process, the volume remains constant. Since work is defined as W=PΔV, where ΔV=0 means no work is performed.
Correct answer: Isochoric condition- A. The temperature decreases
- B. The temperature increases
- C. The temperature remains constant
- D. Temperature increases first then decreases
Explanation: During an adiabatic process, when the volume of a gas decreases, its temperature increases due to the work done on the gas, which raises…
Correct answer: The temperature increases- A. Absorbs heat
- B. Releases heat
- C. Neither absorbs nor releases heat
- D. None of the given options
Explanation: For isothermal expansion of an ideal gas, work is done by the system, and to keep the temperature constant, heat must be absorbed.
Correct answer: Absorbs heat- A. Isothermal steps only
- B. Adiabatic steps only
- C. Both adiabatic and isothermal steps
- D. Neither adiabatic nor isothermal
Explanation: The Carnot cycle consists of two isothermal and two adiabatic processes.These steps are essential for its maximum efficiency.Therefore…
Correct answer: Both adiabatic and isothermal steps- A. Increases
- B. Decreases
- C. Remains the same
- D. Decreases by 0.1 J
Explanation: Since the heat added equals the work done, the internal energy does not change.Therefore, this option is correct.
Correct answer: Remains the same- A. 7900 J
- B. 8200 J
- C. 5600 J
- D. 6400 J
Explanation: Correct. Applying the first law of thermodynamics: ΔU = Q - W Q = 2 kcal = 2000 cal = 2000 × 4.186 J = 8372 J W = 500 J ΔU = 8372 J - 500…
Correct answer: 7900 J- A. 150 J
- B. 70 J
- C. 110 J
- D. 40 J
Explanation: Correct. Applying the first law of thermodynamics: ΔU = Q - W W = Q - ΔU Q = 110 J ΔU = 40 J W = 110 J - 40 J = 70 J
Correct answer: 70 J- A. 166 cal
- B. 333 cal
- C. 500 cal
- D. 400 cal
Explanation: Correct. Using the first law of thermodynamics: ΔU = Q - W Q = ΔU + W Q = 167 cal + 333 cal = 500 cal
Correct answer: 500 cal- A. -5 J
- B. 10 J
- C. 15 J
- D. 5 J
Explanation: The change in internal energy = work done by the system + heat energy supplied to the system. The work done by the system is 5 J.
Correct answer: 5 J- A. Cyclic
- B. Free expansion
- C. Isobaric
- D. Adiabatic
Explanation: The net work done is zero in a free expansion process.In a free expansion, the gas expands into a vacuum.
Correct answer: Free expansion- A. Heat absorbed = work done on the system
- B. Heat absorbed = work done by the system
- C. Heat released = work done by the system
- D. Heat released= work done by the system+ change in internal energy
Explanation: Option A : According to the first law of thermodynamics, heat absorbed is not equal to work done on the system.
Correct answer: Heat absorbed = work done by the system- A. dQ
- B. dW
- C. dQ-dW
- D. dQ+dW
Explanation: In a thermodynamic process, the internal energy (ΔU = ΔQ - ΔW) is a state function, therefore it depends only on the initial and the final…
Correct answer: dQ-dW- A. Isothermal
- B. Adiabatic
- C. Isobaric
- D. Isochoric
Explanation: Isothermal process is the one where temperature remains constant.Isochoric process is the one where volume remains constant.Isobaric…
Correct answer: Adiabatic