Thermodynamics
First Law of Thermodynamics
Energy conservation: ΔU = Q - W (physics convention).
Variables
ΔUJ
Internal energy change
Change in internal energy
In SI units: kg·m²/s²
QJ
Heat added
Heat into system
In SI units: kg·m²/s²
WJ
Work done
Work by system
In SI units: kg·m²/s²
Derivation
Fundamental law of energy conservation.
Your notes
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- Q = 2 J (Heat added)
- W = 3 J (Work done)
Result: ΔU = -1 J
Where this formula is listed
- Thermodynamics formulas, under First Law, alongside Work (Isothermal Process), Internal Energy (Ideal Gas), Adiabatic Process, Heat Capacity Relation and Work (Adiabatic Process).
- In the thermodynamics list it comes after Newton's Law of Cooling and before Work Done by Gas.
- 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 First Law of Thermodynamics formula?
First Law of Thermodynamics is written ΔU = Q − W. Energy conservation: ΔU = Q - W (physics convention). It belongs to Thermodynamics, under First Law.
What are the units in ΔU = Q − W?
In SI units, ΔU is internal energy change, measured in kg·m²/s²; Q is heat added, measured in kg·m²/s²; W is work done, measured in kg·m²/s².
How is the First Law of Thermodynamics formula derived?
Fundamental law of energy conservation. The result is ΔU = Q − W.