13 Jun 2026

Thermodynamics Standard Problems

Standard competitive exam problems in thermodynamics with answer key.

thermodynamics gate-2024 csir-net-2023 jest-2022

These are original standard problems based on frequently tested competitive-exam patterns.

Q: For a reversible isothermal expansion of an ideal gas, the change in internal energy is
A: positive
B: negative
C: zero
D: equal to work done
ANSWER: C
SOURCE: GATE 2024 style
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Q: The efficiency of a Carnot engine operating between $T_h$ and $T_c$ is
A: $T_c/T_h$
B: $1-T_c/T_h$
C: $T_h/T_c-1$
D: $T_h-T_c$
ANSWER: B
SOURCE: CSIR-NET 2023 style
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Q: The thermodynamic identity for a simple compressible system is
A: $dU=TdS-PdV$
B: $dU=PdV-TdS$
C: $dU=SdT+VdP$
D: $dU=TdV-PdS$
ANSWER: A
SOURCE: JEST 2022 style
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Q: The heat capacity difference for one mole of ideal gas is
A: $C_P-C_V=R$
B: $C_V-C_P=R$
C: $C_P+C_V=R$
D: $C_P/C_V=R$
ANSWER: A
SOURCE: GATE 2021 style
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Q: Entropy of an isolated system in a spontaneous process
A: always decreases
B: remains exactly zero
C: never decreases
D: is unrelated to irreversibility
ANSWER: C
SOURCE: CSIR-NET 2020 style
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Q: In an adiabatic reversible process for an ideal gas,
A: $PV^\gamma=\text{constant}$
B: $PV=\text{constant only}$
C: $P/V=\text{constant}$
D: $P+V=\text{constant}$
ANSWER: A
SOURCE: GATE style
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Q: The Gibbs free energy is
A: $G=U-TS$
B: $G=H-TS$
C: $G=TS-PV$
D: $G=PV-U$
ANSWER: B
SOURCE: CSIR-NET style
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Q: At constant temperature and pressure, spontaneous processes minimize
A: internal energy
B: enthalpy only
C: Gibbs free energy
D: volume only
ANSWER: C
SOURCE: JEST style

Problem Sheet Standard MCQs