🔥 Thermodynamics – Stage 3

Page 7 : JEE Advanced Mixed PYQs (Numerical + Reasoning)

These problems require concept linking + approximation + logic. Direct formula application will fail.

PYQ 1️⃣ : Variable Pressure Work Trap

Gas expands with pressure varying as P = a − bV.

Work = ∫ P dV = ∫ (a − bV)dV
= a(V₂−V₁) − b(V₂²−V₁²)/2

❌ Using W = PΔV

PYQ 2️⃣ : Half-Cycle Trap

Gas completes half of a cyclic process.

ΔU ≠ 0 (state not repeated)

❌ Assuming cyclic behavior too early

PYQ 3️⃣ : Maximum Work Condition

Gas expands from P₁ to P₂.

Maximum work → Reversible isothermal

❌ Choosing adiabatic for max work

PYQ 4️⃣ : Carnot Engine Reality Check

Engine working between 400K and 300K.

η_max = 1 − 300/400 = 25%

❌ Expecting real engine efficiency = Carnot

PYQ 5️⃣ : Mixing of Gases Entropy

Two different ideal gases mix.

ΔS > 0 even if temperatures equal

❌ Thinking entropy depends only on temperature

PYQ 6️⃣ : Internal Energy Illusion

Ideal gas compressed isothermally.

ΔU = 0, but Q ≠ 0 and W ≠ 0

❌ Equating ΔU = 0 to no heat transfer

PYQ 7️⃣ : Fast vs Slow Process

Same expansion done fast and slow.

Work differs; final state same

❌ Thinking work is state function

PYQ 8️⃣ : Temperature vs Heat

Two gases absorb equal heat.

ΔT depends on degrees of freedom

❌ Assuming ΔT ∝ Q always

PYQ 9️⃣ : Refrigerator Misconception

Refrigerator removes heat from cold body.

Work input required (always)

❌ Thinking natural heat flow helps refrigerator

PYQ 🔟 : Final JEE Trap Statement

Same ΔT does NOT imply same heat absorbed

✅ Stage 3 – Page 7 Completed
➡️ Next: Stage 3 – Page 8 (Assertion–Reason & Concept Killer Problems)

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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
Set 14
Set 15
Set 16
Set 17
Set 18
Set 19
Set 20
Set 21
Set 22
Set 23
Set 24
Set 25
Set 26
Set 27
Set 28
Set 29
Set 30
Set 31
Set 32
Set 33
Set 34
Set 35
Set 36
Set 37
Set 38
Set 39
Set 40
Set 41
Set 42
Set 43
Set 44
Set 45
Set 46
Set 47
Set 48
Set 49
Set 50
Set 51
Set 52
Set 53
Set 54
Set 55
Set 56
Set 57
Set 59

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