There are a few concepts which work simultaneously and make this happen i.e. cooking food in a short amount of time.
As per Gay- Lussac’s law, at constant volume, pressure is directly proportional to temperature for a system. Now, the temperature inside cooker increases the pressure increases too.
The boiling point of a liquid is the temperature at which its vapor pressure becomes equal to atmospheric pressure. For pure water, this temperature is 1000C. But for the common drinking water this temperature is quite low. That is water starts boiling at lower temperatures hence, the food also is cooking at low temperature only.
Now, with increase in the pressure insider the cooker, the vapor pressure increases and hence the water inside boils are much higher temperature i.e. the temperate of a cooker is much higher than open pan. This cooks food faster.
