🔥 Thermodynamics – Stage 1

Page 6 : PV Diagrams & Area Interpretation (JEE Core)

Golden Rule:
Work done in a thermodynamic process = Area under PV curve

1️⃣ What is a PV Diagram?

A graph between Pressure (P) on Y-axis and Volume (V) on X-axis showing how a gas changes its state during a process.

• Each point → one equilibrium state
• A curve → thermodynamic process

2️⃣ Work Done from PV Diagram

Mathematical Meaning:
W = ∫ P dV

Physical Meaning:
Area enclosed between PV curve and volume axis

⚠ Direction matters:
Expansion → Positive work
Compression → Negative work

3️⃣ PV Diagrams for Important Processes

(a) Isothermal Process

• Curve: Rectangular hyperbola
• Equation: PV = constant
• Area under curve = nRT ln(V₂/V₁)

(b) Adiabatic Process

• Curve steeper than isothermal
• Equation: PV^γ = constant
• Less area than isothermal (for same V change)

Important JEE Insight:
Adiabatic curve always lies below isothermal curve during expansion

(c) Isobaric Process

• Horizontal straight line
• Work = PΔV (area of rectangle)

(d) Isochoric Process

• Vertical straight line
• No area → No work done

4️⃣ Cyclic Process & Area

A cyclic process returns the system to its initial state.

Key Result:
Net work done = Area enclosed by the cycle

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

5️⃣ JEE-Trap Comparisons

Process	PV Curve Shape	Work Done
Isothermal	Hyperbola	Maximum
Adiabatic	Steeper curve	Less than isothermal
Isobaric	Straight horizontal	PΔV
Isochoric	Straight vertical	Zero

6️⃣ JEE Advanced Thinking Tips

• Larger area → More work
• Steeper curve → Less work
• Always check direction of process
• Cycles → Think area, not formulas

👉 Next Page:
Page 7 – First Law of Thermodynamics (ΔQ, ΔU, W Applications)

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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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