Air inside a rigid, thermally-insulated tank undergoes stirring as shown in the figure below. Which one of the following options is correct?

Both the enthalpy and the entropy of the air increase

The enthalpy of the air increases while the entropy of the air remains constant

Both the enthalpy and the entropy of the air remain constant

Both the enthalpy and the entropy of the air increase

The enthalpy of the air decreases while the entropy of the air increases

GATE 2025 Mechanical Engineering Q18 — Mechanical Engineering

GATE 2025Set MasterQ18MCQanswer keyexplanation soonmedium

Mechanical Engineering · Thermodynamics

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Figure from the original GATE 2025 paper. (IIT Roorkee archive)

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Recurring concept

Thermodynamics has appeared in GATE Mechanical Engineering 5 times across 4 years (2019, 2021, 2025, 2026).