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 10 of 15
- A. 1st Law of thermodynamics
- B. 2nd Law of thermodynamics
- C. Law of conservation of energy
- D. Law of entropy
Explanation: An adiabatic process is one where no heat enters or leaves a system. Here, we compress a gas adiabatically inside a bicycle pump.
Correct answer: 1st Law of thermodynamics- A. 7 P1V1
- B. 8 P1V1
- C. 9 P1V1
- D. 10 P1V1
Explanation: In this problem, the process involves the pressure of the gas being proportional to the volume, which suggests a linear relationship.
Correct answer: 9 P1V1- A. 2/5
- B. 3/5
- C. 3/7
- D. 5/7
Explanation: Q=U+wU which is internal energy includes intermolecular interactions, vibrational, rotational, translational kinetic energy.In a monatomic…
Correct answer: 3/5- A. 100%
- B. 300%
- C. 200%
- D. 75%
Explanation: The correct answer is Option D: 75%. The internal energy change of an ideal gas is directly proportional to the change in temperature.
Correct answer: 75%- A. ∆Q=∆W
- B. ∆Q=∆U+∆W
- C. ∆Q=∆U
- D. ∆Q=∆U/∆W
Explanation: The correct expression for the 1st law of thermodynamics is ∆Q=∆U+∆W, which states that the heat energy added to a system (∆Q) is equal to…
Correct answer: ∆Q=∆U+∆W- A. The heating of a system equals the increase of its internal energy plus the work done on the system
- B. The increase in the internal energy of a system equals the heating of the system minus the work done by the system
- C. The increase in the internal energy of a system equals the heating of the system plus the work done by the system
- D. The work done on a system equals the increase of its thermal energy plus the heating of the system
Explanation: The first law of thermodynamics is essentially a statement of energy conservation.
Correct answer: The increase in the internal energy of a system equals the heating of the system minus the work done by the system- A. ∆U is positive, Q is zero, W is positive
- B. ∆U is negative, Q is zero, W is negative
- C. ∆U is zero, Q is zero, W is positive
- D. ∆U is positive, Q is positive, W is zero
Explanation: When the balloon bursts, the gas undergoes rapid adiabatic expansion, meaning there is no heat exchange with the surroundings (Q = 0).
Correct answer: ∆U is negative, Q is zero, W is negative- A. Qx = Qy and Ux = Uy
- B. Qx = Qy and Ux < Uy
- C. Qx < Qy and Ux < Uy
- D. Qx < Qy and Ux = Uy
Explanation: When heating occurs at constant volume, all the heat added increases the internal energy, whereas at constant pressure, some heat…
Correct answer: Qx < Qy and Ux = Uy- A. Decreases
- B. First increases and then decreases
- C. Increases
- D. Remains the same
Explanation: The correct answer is D: Remains the same. For an ideal gas, internal energy is a function of temperature only (U ∝ T).
Correct answer: Remains the same- A. 50J
- B. 90J
- C. 60J
- D. 110J
Explanation: The problem is solved using the first law of thermodynamics, which states that the change in internal energy (∆U) is equal to the heat…
Correct answer: 50J- A. Increases
- B. Remains constant
- C. Decreases
- D. Becomes Zero
Explanation: When objects are rubbed together, mechanical work is done on them, which increases their temperature.
Correct answer: Increases- A. 31.4J
- B. 3.14 x 10^7 J
- C. 3.14J
- D. None
Explanation: Q=∆U+W cyclic process i.e. ∆U=0 Q=W=Area pf P-V graph= πr² =π(Pr)(Vr) =3.14(100x103)(100)=31.4x106 J
Correct answer: 3.14 x 10^7 J- A. Isothermal
- B. Isobaric
- C. Isochoric
- D. Adiabatic
Explanation: The correct answer is Isochoric because in an isochoric process, the volume of the system remains constant, meaning no work is done by or…
Correct answer: Isochoric- A. AB, BC, CD
- B. DC, CB, BA
- C. CD, DA, AB
- D. BA, AD, DC
Explanation: In the pressure-volume diagram, an isochoric process is characterized by a constant volume (ΔV=0), which corresponds to a vertical line.
Correct answer: DC, CB, BA- A. A
- B. B
- C. C
- D. D
Explanation: During X--->Y, V↓,P↑During Y--->Z P∝1/VDuring Z--->X P=constant V↓
Correct answer: D- A. 2 J
- B. 1 J
- C. -2 J
- D. -1 J
Explanation: In an adiabatic process, there is no heat exchange with the surroundings (Q = 0).
Correct answer: 2 J- A. 100 kJ
- B. 10 kJ
- C. 0 kJ
- D. 1 kJ
Explanation: The correct answer is 10 kJ because, according to the first law of thermodynamics, the change in internal energy (∆U) is equal to the heat…
Correct answer: 10 kJ- A. -100 J
- B. 0 J
- C. +100 J
- D. None
Explanation: In an adiabatic process, there is no heat exchange with the surroundings (Q = 0).
Correct answer: +100 J- A. T decreases
- B. Mechanical energy goes out of the system
- C. Q=constant
- D. All of these
Explanation: The correct answer is D because during an adiabatic expansion:A) The temperature (T) of the system decreases.B) Mechanical energy goes out…
Correct answer: All of these- A. Isothermal expansion
- B. Energy dissipation
- C. Adiabatic expansion
- D. Adiabatic compression
Explanation: The correct answer is Adiabatic expansion. In this process, the air escaping from the punctured football expands rapidly without…
Correct answer: Adiabatic expansion