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Cheat sheet · Class 11 · CBSE · Science Physics

Thermodynamics cheat sheet

The whole chapter on one page: key formulas, facts and the points to remember, for quick revision before a test.

CBSE Class 11 · Physics

Cheat sheet

Chapter 11Thermodynamics

ΔQ = ΔU + ΔW — heat in = internal energy up + work out.

1. Laws

Zeroth law

Two systems each in equilibrium with a third are in equilibrium with each other — defines temperature.

First law

ΔQ=ΔU+ΔW\Delta Q = \Delta U + \Delta W (energy conservation).

Second law

No engine is 100% efficient; heat doesn't flow cold → hot by itself (Kelvin–Planck, Clausius).

2. Processes (ideal gas)

ProcessConstantWork done
IsothermalTμRTln⁡V2V1\mu RT\ln\dfrac{V_2}{V_1}
AdiabaticQ = 0μR(T1−T2)γ−1\dfrac{\mu R(T_1 - T_2)}{\gamma - 1}
IsobaricPPΔVP\Delta V
IsochoricV0

Adiabatic: PVγPV^\gamma = constant, γ=Cp/Cv\gamma = C_p/C_v.

3. Engines & Refrigerators

η=1−Q2Q1\eta = 1 - \dfrac{Q_2}{Q_1}ηCarnot=1−T2T1\eta_{Carnot} = 1 - \dfrac{T_2}{T_1}
α=Q2W\alpha = \dfrac{Q_2}{W} (coefficient of performance)

4. Key Points

  • U of an ideal gas depends only on T.
  • Carnot engine: 2 isothermal + 2 adiabatic.
  • Reversible processes are idealisations.
  • Heat and work are path functions; U is a state function.

Remember: ΔQ = ΔU + ΔW | 4 processes | Carnot η = 1 − T₂/T₁

Thermodynamics: questions and notes

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