This law is named after Jacques Charles (1746–1823), a French physicist who discovered that all
gases increase in volume by the same proportion if heated through the same temperature range, provided
that the pressure remained constant. This proportion is 1/273 of their volume at freezing point
(0◦C or 273K) for each 1K rise above 273K. Therefore, the temperature of a volume of gas would
need to be increased from 0◦C to 273◦C in order to double its volume. (Note: 1K rise = 1◦C rise.)
Where the pressure remains constant, Charles’s law is expressed as:
Volume ÷ Temperature = Constant
In simple terms, if the temperature increases, so does the volume. As with Boyle’s law, the formula
can be redefined as:
V1 ÷ T1 = V2 ÷ T2
Where V1 = original volume, T1 = original temperature, V2 = final volume and T2 = final temperature.
Practical example If 1 m3 of gas enters a building from outside where the temperature is 2◦C and
passes into a building where the temperature is 21◦C, the gas would increase in volume by:
V1 ÷ T1 = V2 ÷ T2, so (V1 × T2) ÷ T1 = V2
∴ 1 × (21 + 273) ÷ (2 + 273) = 1.07 m3, an increase of 7%
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