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Mechanical Engineering Exam  >  Mechanical Engineering Test  >  Thermodynamics  >  Test: Entropy - 3 - Mechanical Engineering MCQ

Entropy - 3 - Free MCQ Practice Test with solutions, GATE ME Thermodynamics


MCQ Practice Test & Solutions: Test: Entropy - 3 (15 Questions)

You can prepare effectively for Mechanical Engineering Thermodynamics with this dedicated MCQ Practice Test (available with solutions) on the important topic of "Test: Entropy - 3". These 15 questions have been designed by the experts with the latest curriculum of Mechanical Engineering 2026, to help you master the concept.

Test Highlights:

  • - Format: Multiple Choice Questions (MCQ)
  • - Duration: 45 minutes
  • - Number of Questions: 15

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Test: Entropy - 3 - Question 1
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In a reversible cycle, the entropy of the system

Test: Entropy - 3 - Question 2
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​Entropy may be expressed as a function of

Detailed Solution: Question 2

  • Entropy is a measure of disorder or randomness in a system.
  • It can be expressed in several ways, depending on the variables involved:
  • Pressure and temperature: Entropy changes with alterations in pressure and temperature, especially in gases.
  • Temperature and volume: In thermodynamic processes, entropy is influenced by changes in volume and temperature.
  • Heat and work: Entropy is related to the heat transferred and the work done in a system.
  • Thus, entropy can indeed be expressed as a function of all these variables.

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Test: Entropy - 3 - Question 3
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Clausius inequality is stated as

Detailed Solution: Question 3

If  Cycle is reversible
If Cycle is irreversible
If Cycle is impossible
Hence
For cycle is possible 
This is known as Clausius inequality.

Test: Entropy - 3 - Question 4
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When a system undergoes a process such that  and ΔS > 0, the process is

Test: Entropy - 3 - Question 5
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A certain amount of fluid at temperature T1 is mixed with an equal amount of the same fluid at temperature T2 in an insulated container with total fluid as the system, consider the following statements
I. Energy of the system is conserved
II. Entropy of the system is conserved
III. Entropy of the system increases
IV. Entropy of the system decreases
Q. Which of the above statements is/are true?

Test: Entropy - 3 - Question 6
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Which one of the following statements applicable to a perfect gas will also be true for an irreversible process

Detailed Solution: Question 6

δQ = dU+ PdV... Applicable for a closed system when only PdV work is present. This is true only for a reversible process.
δQ = TdS ...Applicable for a reversible process.
TdS = dU + PdV... Applicable for any process reversible or irreversible, undergone by a closed system, since it is a relation among properties which are independent of the path.

Test: Entropy - 3 - Question 7
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The entropy change for any closed system which undergoes an irreversible adiabatic process

Test: Entropy - 3 - Question 8
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Consider two subsystem 1 and 2 containing same fluid and having same mass m; but at Temperature T1 and T2(T1 > T2) enclosed in an adiabatic enclosure separate by a partition, if the partition is removed and the fluids are allowed to mix. The entropy change of process is

Detailed Solution: Question 8

Subsystem 1 having a fluid of mass m1 specific heat c1 and temperature t1 and subsystem 2 consisting of a fluid of mass m2, specific heat c2, and temperature t2, comprise a composite system in an adiabatic enclosure figure. When the partition is removed, the two fluids mix together, and at equilibrium let tf be the final temperature, and t2 < tf < t1 Since energy interaction is exclusively confined to the two fluids, the system being isolated

∴  

Entropy change for the fluid in subsystem1,

This will be negative, since T1 > Tf
Entropy change for the fluid in subsystem 2

This will be positive, since T2 < Tf

ΔSuniv will be positive definite, and the mixing process is irreversible.
Although the mixing process is irreversible, to evaluate the entropy change for the subsystem, the irreversible path was replaced by a reversible path on which the integration was performed.

Test: Entropy - 3 - Question 9
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For the isentropic expansion of an ideal gas from the initial conditions P1,T1 to the final conditions P2,T2, which one of the following relations is valid?

Detailed Solution: Question 9

For isentropic expansion, PVγ = constant

from ideal gas law,


Also, 

Test: Entropy - 3 - Question 10
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The change in entropy of the system, ΔSsys, undergoing a cyclic irreversible process is

Detailed Solution: Question 10

The change in entropy of a system, represented as ΔSsys, during a cyclic irreversible process is characterised by the following:

  • In an irreversible process, the entropy of the system increases.
  • This means that ΔSsys is always greater than zero.
  • For a cyclic process, the overall change in entropy of the system after one complete cycle is zero.
  • However, during the individual cycles, the entropy can still increase due to irreversibilities.

Thus, in summary, the entropy change of the system is indeed greater than zero during the process.

Test: Entropy - 3 - Question 11
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In a reversible isothermal process, an ideal gas expands to four times its initial volume. The change in entropy is

Test: Entropy - 3 - Question 12
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High pressure steam is expanded adiabatically and reversible through a well insulated turbine which produces some shaft work. If the enthalpy change and entropy change across the turbine are represented by ΔH and ΔS, respectively, for this process:

Detailed Solution: Question 12

For reversible adiabatic process, ΔS = 0 but ΔH ≠ 0.

Test: Entropy - 3 - Question 13
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A system undergo a state change from 1 to 2, according to second law of thermodynamics for the process to be feasible, the entropy change (S2 - S1) of the system

Test: Entropy - 3 - Question 14
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The following four figure have been drawn to represent a fictitious thermodynamic cycle, on P - V and T - S planes




According to first Saw of thermodynamics, equal areas are enclosed by

Detailed Solution: Question 14

We know that:
For closed cycle change in internal energy is zero First law of thermodynamic for closed system

Hence, equal area are enclosed by figures 1 and 2.

Test: Entropy - 3 - Question 15
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Four process of thermodynamic cycle are shown in figure on P-V diagram in the sequence 1 -2-3-4. The corresponding correct sequence of these process in the T-S plane shown in figure will be

Detailed Solution: Question 15

Explanation:


  • Process 1-2: This process is represented by line AB in the T-S diagram. It is an isentropic compression process where the gas is compressed adiabatically and reversibly.

  • Process 2-3: This process is represented by line BC in the T-S diagram. It is an isobaric heat addition process where the gas absorbs heat at constant pressure and the temperature and entropy increase.

  • Process 3-4: This process is represented by line CD in the T-S diagram. It is an isentropic expansion process where the gas expands adiabatically and reversibly, doing work on the surroundings.

  • Process 4-1: This process is represented by line DA in the T-S diagram. It is an isochoric heat rejection process where the gas releases heat at constant volume and the temperature and entropy decrease.


    •  

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About this Mechanical Engineering Practice Test

This test contains 15 MCQs on Entropy - 3 with detailed solutions for each question. It is part of the Thermodynamics course on EduRev, designed to align with the current Mechanical Engineering syllabus. Each solution explains not just the correct answer but also gives you an understanding of the topic — not just to attempt the question but also help you prepare for the exam with practice.

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