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Revise: Heat Transfer and Thermodynamics

How heat moves, the first law of thermodynamics, and how heat engines convert heat into work.

Mechanisms of Heat Transfer

Conduction, convection, radiation. Q/t = kA(ΔT)/d for conduction.

k=50,A=0.02,ΔT=100,d=0.5 → 200W.

Radiation and the Stefan-Boltzmann Law

P = εσAT⁴ — T must be in kelvin.

ε=0.9,A=0.5,T=400K → P≈653.2W.

Internal Energy and Work

W = PΔV — area under a horizontal P-V line.

P=200000Pa, ΔV=0.03m³ → W=6000J.

The First Law of Thermodynamics

ΔU = Q−W — energy conservation.

Q=8000J, W=6000J → ΔU=2000J.

Heat Engines and Efficiency

η = W/Qₕ = 1−Qc/Qₕ.

Qₕ=5000J, Qc=3000J → η=40%.