# Isentropic process is related to

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3. Isothermal Expansion
4. Reversible Isothermal Expansion

Option 2 : Reversible Adiabatic Expansion
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## Detailed Solution

Concept:

In thermodynamics, an isentropic process is an idealized thermodynamic process that is both adiabatic and reversible. The work transfers of the system are frictionless, and there is no transfer of heat or matter.

$$dS = \frac{{d{Q_{rev}}}}{T}$$

If the process is reversible and adiabatic: dQrev = 0 ⇒ dS = 0

$${Q_{rev}} = \smallint TdS$$

Entropy analysis for a closed system:

$$ds=(\frac{\delta Q}{T} )+ (\delta S)_{gen}$$

Case 1: For internally reversible process (δs)gen = 0

• When heat is added to the system ⇒ (δQ) = +ve ⇒ ds = +ve
• When heat is rejected from the system ⇒ (δQ) = -ve ⇒ ds = -ve
• For adiabatic process ⇒ (δQ) = 0 ⇒ ds = 0 (ISENTROPIC)

Case 2: For internally irreversible process (δs)gen ≠ 0 ⇒ (δs)gen = +ve

• When heat is added to the system ⇒ (δQ) = +ve ⇒ ds = +ve
• When heat is rejected from the system ⇒ (δQ) = -ve ⇒ ds = -ve or +ve or zero
• Since (δs)gen = +ve and (δQ) = -ve so change in entropy, ds can be zero is (δQ/T) = δs)gen, In this case, the process will be ISENTROPIC
• For adiabatic process ⇒ (δQ) = 0 ⇒ ds = +ve

Thus for a process to be isentropic there are two cases:
The text passage is a multiple-choice question from an exam, followed by a detailed explanation of the concept of an isentropic process in thermodynamics.
no_question

the passage does not contain a mathematical question or calculation. it provides a multiple-choice question and a detailed explanation of a thermodynamic concept.
Given a text passage, determine:
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    2. If an answer to that mathematical question is provided in the text

First, describe the content structure you found in 1-2 sentences.

Then provide your analysis in the following format:
TYPE: <one of the following values>
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system
# Isentropic process is related to

This question was previously asked in
ISRO Scientist ME 2017 (II) Official Paper
View all ISRO Scientist ME Papers >
3. Isothermal Expansion
4. Reversible Isothermal Expansion

Option 2 : Reversible Adiabatic Expansion
Free
ISRO Scientist Mechanical FT 1
1.6 K Users
95 Questions 100 Marks 120 Mins

## Detailed Solution

Concept:

In thermodynamics, an isentropic process is an idealized thermodynamic process that is both adiabatic and reversible. The work transfers of the system are frictionless, and there is no transfer of heat or matter.

$$dS = \frac{{d{Q_{rev}}}}{T}$$

If the process is reversible and adiabatic: dQrev = 0 ⇒ dS = 0

$${Q_{rev}} = \smallint TdS$$

Entropy analysis for a closed system:

$$ds=(\frac{\delta Q}{T} )+ (\delta S)_{gen}$$

Case 1: For internally reversible process (δs)gen = 0

• When heat is added to the system ⇒ (δQ) = +ve ⇒ ds = +ve
• When heat is rejected from the system ⇒ (δQ) = -ve ⇒ ds = -ve
• For adiabatic process ⇒ (δQ) = 0 ⇒ ds = 0 (ISENTROPIC)

Case 2: For internally irreversible process (δs)gen ≠ 0 ⇒ (δs)gen = +ve

• When heat is added to the system ⇒ (δQ) = +ve ⇒ ds = +ve
• When heat is rejected from the system ⇒ (δQ) = -ve ⇒ ds = -ve or +ve or zero
• Since (δs)gen = +ve and (δQ) = -ve so change in entropy, ds can be zero is (δQ/T) = δs)gen, In this case, the process will be ISENTROPIC
• For adiabatic process ⇒ (δQ) = 0 ⇒ ds = +ve

Thus for a process to be isentropic there are two cases:
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The text passage is a multiple-choice question from an exam, followed by a detailed explanation of the concept of an isentropic process in thermodynamics.

TYPE: NO_QUESTION

The passage does not contain a mathematical question or calculation. It provides a multiple-choice question and a detailed explanation of a thermodynamic concept.