Thermodynamics
Clausius Inequality
Entropy change is at least Q/T. Equality holds for reversible processes.
Variables
ΔSJ/K
Entropy change
Change in entropy
In SI units: kg·m²/(s²·K)
QJ
Heat transfer
Heat added to system
In SI units: kg·m²/s²
TK
Temperature
Temperature of reservoir
Derivation
From second law: for irreversible processes, entropy generation > 0, so ΔS > Q/T.
Your notes
0/5000
Other thermodynamics formulas with the same quantities
- Stefan-Boltzmann Law (Heat & Temperature) shares Temperature
- Work (Isothermal Process) (First Law) shares Temperature
- Internal Energy (Ideal Gas) (First Law) shares Temperature
- Ideal Gas Law (Kinetic Theory) shares Temperature
- Ideal Gas Law (Molecular) (Kinetic Theory) shares Temperature
- Average Kinetic Energy (Gas) (Kinetic Theory) shares Temperature
Where this formula is listed
- Thermodynamics formulas, under Second Law, alongside Heat Engine Efficiency, Coefficient of Performance (Refrigerator) and Coefficient of Performance (Heat Pump).
- In the thermodynamics list it comes after Coefficient of Performance (Heat Pump) and before Ideal Gas Law.
- Thermodynamics formula sheet, one of 34 formulas printed with symbol keys and SI units.
- The full formula index, grouped by category and topic.
Common questions
What is the Clausius Inequality formula?
Clausius Inequality is written ΔS ≥ Q/T. Entropy change is at least Q/T. Equality holds for reversible processes. It belongs to Thermodynamics, under Second Law.
What are the units in ΔS ≥ Q/T?
In SI units, ΔS is entropy change, measured in kg·m²/(s²·K); Q is heat transfer, measured in kg·m²/s²; T is temperature, measured in K.
How is the Clausius Inequality formula derived?
From second law: for irreversible processes, entropy generation > 0, so ΔS > Q/T. The result is ΔS ≥ Q/T.