Free First Law of Thermodynamics MCQs with Answers

• A. Then the work is done by the gas
• B. Internal energy of the gas increases
• C. Both A and B
• D. None of these

Explanation: Properties of isobaric process. When heat is added to a gas in an isobaric process, a part of it is used to do external work while the…

• A. Positive in all cases (i) to (iv)
• B. Negative in cases (i), (ii) and (iii) but zero in (iv) case
• C. Positive in cases (i), (ii) and (iii) but zero in (iv) case
• D. Zero in all four cases

Explanation: In case of any cyclic process change in internal energy is zero. Here, the given four diagrams are representing the cyclic process.

• A. Totally K.E
• B. Partly K.E and partly P.E
• C. Totally P.E
• D. Neither K.E nor P.E

Explanation: The internal energy changes in an ideal gas can be described solely by change in its kinetic energy.

• A. A
• B. B
• C. C
• D. D

Explanation: For an isothermal process, the heat added to an ideal system versus work performed by that system is represented graphically as a straight…

• A. It is sum of all forms of molecular energies of a system
• B. It is a state function of a system
• C. It is proportional to transnational K.E of the molecules
• D. All of the above

Explanation: All of the these options are properties of internal energy

• A. The internal energy changes in all processes
• B. The change in entropy can never be zero
• C. Internal energy and entropy are state functions
• D. The work done in an adiabatic process is always zero

Explanation: State functions are properties that depend only on the current state of a system, not on the path taken to reach it.

• A. First law of thermodynamics
• B. Second law of thermodynamics
• C. Newton law of motion
• D. Entropy

Explanation: According to the Second Law of Thermodynamics, heat will always flow spontaneously from hot to cold, and never the other way around.

• A. Increased by 80 joules
• B. Decreased by 80 joules
• C. Increased by 20 joules
• D. Decreased by 20 joules
• E. Remained constant

Explanation: Apply 1st Law of Thermodynamics∆E = q - where,∆E = 30J - (+50) (work is done BY the system)∆E = -20Ji.e Internal energy decreased by 20…

• A. Change in internal energy (ΔU)
• B. Change in enthalpy (ΔH)
• C. Change in free energy (ΔG)
• D. Change in temperature only (ΔT)
• E. Change in pressure only (ΔP)

Explanation: At constant pressure, the heat added to a system is equal to the change in enthalpy (ΔH).

• A. Decreases
• B. Increases
• C. Becomes zero
• D. Remain constant

Explanation: In an isothermal process the internal energy remains constant so the temperature remains constant.In an Isobaric process,the pressure…

• A. Positive in each case
• B. Negative for I and positive for II
• C. Positive for I and negative for II
• D. Zero in each case
• E. Zero in I and positive for II

Explanation: An adiabatic process is a thermodynamic process that involves the transfer of energy without transfer of heat or mass to the surrounding…

• A. PV𝛾 = constant
• B. PV𝛾 = RT
• C. P/V𝛾 = RT/n
• D. PV𝛾 = nRT

Explanation: The adiabatic relation between pressure and v."PV𝛾 = Constant".Where 𝛾 is the specific heat ratio, i.e., 𝛾 = Cp/Cv.

• A. Change in pressure
• B. Change in temperature
• C. Change in volume
• D. All of these options are correct

Explanation: In an adiabatic process, the system is insulated so that no heat is exchanged with the surroundings.

• A. 1-(Q2/Q1)
• B. 1+(Q2/Q1)
• C. 1-(Q1/Q2)
• D. 1+(Q1/Q2)

Explanation: Correct option:AThe efficiency of a heat engine is defined as the ratio of the work output to the heat input.

• A. Q = ΔU +W
• B. Q + ΔU = W
• C. Q = ΔU - W
• D. Q = ΔU x W

Explanation: The first law of thermodynamics can be stated as: Q = ΔU + Wwhere Q represents the heat added to the system, ΔU represents the change in…

• A. No heat is added or taken out of the system
• B. No change of temperature takes place
• C. Boyle's law is applicable
• D. Pressure and volume remains constant

Explanation: An adiabatic process is one in which there is no heat exchange with the surroundings.

• A. Q = U
• B. U = W
• C. Q = U/W
• D. Q = W

Explanation: Since it is an isothermal process, there is no change in temperature hence the internal energy is constant.

• A. fallen, since more molecules bombarded the container and so they must be moving slower
• B. fallen, since more molecules collide more frequently with one another and so their average speed is lower
• C. remained constant if the compression is very slow
• D. risen, since doing work on the gas increases the kinetic energy of the molecules
• E. risen, since there are more intermolecular collisions and so more heat is produced by them

Explanation: When a gas in a thermally insulated container is compressed, work is done on the gas, and no heat is lost to the surroundings.

• A. Decreases
• B. Increases
• C. Become zero
• D. Remain constant

Explanation: In an isothermal process, the temperature of the system remains constant.

• A. Risen
• B. Decreased
• C. Remained constant
• D. Cannot be determined

Explanation: This is the correct answer. When a gas is compressed in a thermally insulated container (adiabatic process), work is done on the gas.