Physics Laws & Theorems
Intermediate

Zeroth Law of Thermodynamics

Two systems in thermal equilibrium with a third are in equilibrium with each other.

Formula

A=B, B=C⇒A=CA = B, \ B = C \Rightarrow A = C

Variables

A,B,CSystems (temperatures)

Example

If two cups of coffee each match a thermometer’s reading, they are the same temperature.

Did You Know?

The zeroth law was named last but is so fundamental it had to come "before" the first — it defines temperature.

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