Boyle's Law

Boyle’s Law describes the relationship between the pressure (P) and the volume (V) of a gas, saying that only when the temperature (T) is constant, pressure and volume are two inversely proportional parameters. For gases, when the temperature is constant and the pressure increases, the volume will drop. In the same way, when the pressure decreases at a constant temperature, the volume of that gas will rise.

Robert Boyle determined this relation as one of the Three Gas Laws. This law is often used to compare two different situations with the same gas to figure out one of the parameters when the other changes at a constant temperature. The formula used to explain this relation between pressure and volume is: P₁V₁=P₂V₂ P one per V one is equal to P two times V two

Figure 1. Comparison between two tanks containing the same gas. When the volume decreases, the gas has less space, and its pressure increases.

During inhalation, the air gets slightly warmed up. The volume of the gas is adjusted to match the internal body temperature, which will be kept constant, helping in the pressure-volume relationship of Boyle’s law.