🔥 Thermodynamics – Objective Page 10

FINAL IIT Advanced Level • Mixed Concepts • PYQ Logic

✔ Multi-law questions
✔ No direct formula usage
✔ Think like IIT examiner

🧠 Q1. Impossible Process Identification

Which process is impossible?

100% heat → work in cyclic engine ❌
Work → heat completely ✔

Reason: Second law violation.

🧠 Q2. Engine + Refrigerator Combo

An engine drives a refrigerator.

Total entropy of universe ≥ 0
System entropy may decrease

IIT Focus: Always judge universe, not subsystem.

🧠 Q3. Heat Exchange Between Bodies

Two bodies at different temperatures exchange heat:

ΔS_hot < 0
ΔS_cold > 0
ΔS_total > 0

Key: Direction decided by entropy, not energy.

🧠 Q4. Cyclic Process Trap

For any cyclic process:

ΔU = 0
Q = W

Trap: Q and W need not be zero.

🧠 Q5. Entropy Change at Constant Temperature

At constant temperature:

ΔS depends on heat absorbed
Independent of path only if reversible

PYQ Favorite.

🧠 Q6. Multiple Correct Logic

Select correct statements:

Entropy is state function ✔
Heat is state function ❌
Work is state function ❌
Internal energy is state function ✔

🧠 Q7. Sudden Expansion of Gas

Sudden expansion:

Irreversible
Entropy increases
Temperature may drop or stay same

Depends on constraints.

🧠 Q8. Real Gas vs Ideal Gas

Ideal gas:

U depends only on T
No intermolecular force

Real gas: U depends on T and V.

🧠 Q9. Maximum Efficiency Condition

Efficiency is maximum when:

Process is reversible
Temperature difference is maximum

Carnot principle.

🧠 Q10. Ultimate IIT Elimination Rule

Always check:

Energy conservation
Entropy law

If any option violates → eliminate immediately.

✅ Objective Page 10 Completed
🏁 THERMODYNAMICS – FULLY MASTERED

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🔥 Thermodynamics – Objective Final Revision

Thermodynamics – Set 1
Set 2
Set 3
Set 4
Set 5
Set 6
Set 7
Set 8
Set 9
Set 10
Set 11
Set 12
Set 13
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