🔥 Thermodynamics – Stage 2

Page 7 : Cyclic Process & Heat Engine (JEE Advanced)

This page is extremely high-weight for JEE Advanced. Almost every year → Work = Area based questions appear.

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1️⃣ What is a Cyclic Process?

A thermodynamic process in which the system returns to its initial state.

👉 Initial state = Final state
👉 ΔU = 0 (very important!)

Key Result:
Net Heat Supplied = Net Work Done

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2️⃣ Work Done in a Cyclic Process

✔ Work done in a cycle = Area enclosed by the P–V curve

Clockwise cycle → Work done by gas (Positive)
Anticlockwise cycle → Work done on gas (Negative)

⚠ JEE trap: Direction of loop decides sign of work

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3️⃣ Heat Engine – Basic Idea

A heat engine converts heat energy into mechanical work.

It works in a cycle between two reservoirs.

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4️⃣ Parts of a Heat Engine

• Hot Reservoir (Temperature T₁)
• Working Substance (Gas)
• Cold Reservoir (Temperature T₂)

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5️⃣ Heat Engine Energy Flow

Heat absorbed from source = Q₁
Heat rejected to sink = Q₂
Work done = W

Energy balance:
Q₁ = W + Q₂

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6️⃣ Efficiency of a Heat Engine

Efficiency (η) = Work Output / Heat Input

η = W / Q₁ = (Q₁ − Q₂) / Q₁

⚠ η can never be 100%

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7️⃣ Important JEE Advanced Observations

• No engine can convert all heat into work
• Some heat must be rejected
• Efficiency depends on reservoirs, not working substance
• Larger enclosed area → more work

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8️⃣ Ranker’s One-Line Rules

ΔU = 0 → CYCLIC PROCESS
Area inside P–V loop → WORK DONE
Clockwise loop → ENGINE

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✅ Stage 2 – Page 7 Completed
➡️ Next: Stage 2 – Page 8 : Refrigerator & Heat Pump (COP, JEE Traps)

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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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📘 Complete Physics Libraries

• SHM – Complete Library
• Waves – Objective Library
• Gravitation – Complete Library
• Momentum & Collisions
• Centre of Mass
• Work, Energy & Power
• WEP – Intermediate Notes
• Motion in a Plane

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🔗 Learning Hubs & Community

• IIT–JEE Physics Master Library
• Physics Mega Library
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• Shaktimatha Learning Resource Hub
• WhatsApp Learning Channel

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