A pressure cooker works on the principle of

A pressure cooker operates on the fundamental principle that the boiling point of a liquid increases as the ambient pressure increases. In a sealed pressure cooker, steam generated from heating the water is trapped inside, which significantly raises the internal pressure. Under normal atmospheric pressure (14.7 psi), water boils at 100°C; however, inside a pressure cooker, the pressure can double, raising the boiling point to approximately 121°C. This elevation of the boiling point allows the water to reach a much higher temperature before turning into steam, which in turn transfers more thermal energy to the food, drastically reducing cooking time. While the high temperature and pressure do soften food grains, the core physical principle governing the device's function is the pressure-induced elevation of the boiling point.

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 3: Geological Time Scale The Evolution of The Earths Surface > 3. Geological Time Scale – The Evolution of The Earth's Surface > p. 43