🌡️ Thermodynamics – Stage 2

Page 2 : Advanced P–V Graphs & Work Calculation (JEE Advanced)

In JEE Advanced, P–V graphs are weapons. If you read them correctly, half the problem is solved.

1️⃣ Work Done from P–V Graph (Core Rule)

Work done = Area under the P–V curve
(between initial and final volumes)

👉 Larger enclosed area → more work done

2️⃣ Straight Line P–V Process (Hidden Favorite)

If pressure varies linearly with volume:

Work done = Area of trapezium

Formula:
W = (P₁ + P₂)/2 × (V₂ − V₁)

⚠ Many students wrongly use isothermal formula here

3️⃣ Curved P–V Graphs (Estimation Technique)

If equation is unknown:

Divide area into strips
Approximate using rectangles/trapeziums
Estimate logically (IIT accepts this)

4️⃣ Cyclic Processes (Very High Yield)

For a cyclic process:

ΔU = 0

Therefore:
Q = W

👉 Net work = Area enclosed by loop

5️⃣ Direction of Loop = Sign of Work

Clockwise loop → Work done by gas (+)
Anticlockwise loop → Work done on gas (−)

⚠ This is a very common JEE Advanced trap

6️⃣ Comparing Different Paths (Same States)

Two paths, same initial & final states:

ΔU is same
Work is different
Heat exchanged is different

👉 Path matters for Q and W, not for ΔU

7️⃣ Visual Shortcut (Toppers’ Trick)

Before calculation, ask:

Is expansion more at high pressure?
Which path encloses more area?

👉 Bigger area always wins

8️⃣ IIT-Level Mistakes to Avoid

❌ Ignoring graph scale
❌ Forgetting direction of cycle
❌ Applying wrong process formula

✅ Stage 2 – Page 2 Complete
👉 Next: Stage 2 – Page 3 : First Law in Multi-Process Systems

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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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