Thermodynamics Laws
Fundamental laws describing energy conversion and transfer, forming the basis of physics and engineering. Including four major laws: Zeroth, First, Second, and Third Laws.
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First Law: Conservation of Energy
🔥 Four Laws of Thermodynamics
Zeroth Law:
If A is in thermal equilibrium with B, and B with C, then A is in thermal equilibrium with C. Defines temperature.
If A is in thermal equilibrium with B, and B with C, then A is in thermal equilibrium with C. Defines temperature.
First Law:
ΔU = Q - W
Conservation of energy - energy cannot be created or destroyed.
ΔU = Q - W
Conservation of energy - energy cannot be created or destroyed.
Second Law:
ΔS ≥ 0
Entropy increases - heat cannot spontaneously flow from cold to hot.
ΔS ≥ 0
Entropy increases - heat cannot spontaneously flow from cold to hot.
Third Law:
Absolute zero (0K) is unattainable, and entropy approaches zero at absolute zero.
Absolute zero (0K) is unattainable, and entropy approaches zero at absolute zero.
⚡ Conservation of Energy
The change in internal energy equals heat absorbed minus work done.
- ΔU: Change in internal energy
- Q: Heat absorbed
- W: Work done
- Perpetual motion machines are impossible
📈 Entropy and Disorder
Entropy measures system disorder; entropy of isolated systems never decreases.
- Entropy increase: system tends to disorder
- Irreversible process: entropy increases
- Reversible process: entropy unchanged
- Thermodynamic explanation of time's arrow
🔄 Heat Engine Efficiency
Carnot cycle gives the maximum efficiency of an ideal heat engine.
- η = 1 - T₂/T₁
- T₁: Temperature of hot reservoir
- T₂: Temperature of cold reservoir
- Actual efficiency is always less than Carnot efficiency