Physics Laws & Theorems
Intermediate

First Law of Thermodynamics

Energy conservation: change in internal energy equals heat added minus work done.

Formula

ΔU=Q−W\Delta U = Q - W

Variables

\Delta UInternal energy change
QHeat added
WWork done

Example

Add 100 J of heat and let the gas do 30 J of work — its internal energy rises 70 J.

Did You Know?

The first law is just conservation of energy applied to heat — you can't get energy from nothing.

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