Question

what is the principle used in pressure cooker

Answer 1

Pressure cookers work on the principle that when the pressure increases boiling point of water increases and the steam is produced from water. it helps in controlling the escape of steam. 
hope this will help

Answer 2

The major principle that lies in a ‘pressure cooker’ is the steam pressure.

The stem builds up inside a sealed cooked pot, which increases that ‘boiling point’ of the water trapped inside. This pressure along with the steam enables food to be ‘cooked faster’.

The pressure cooker has a major advantage that is it stores the heat liable nutrients to an extent, due to the shorter cooking time and its sealed nature prevents the nutrients from evaporating.