IN SCHOOL

Steaming success

The pressure cooker is a celebrity in every household.

Do ask your grandmom how much time was spent cooking rice and dal before the advent of the pressure cooker. Not only does it save time and fuel, it also retains the nutritive value and the flavours of food.

The science of pressure cooking follows gas laws. In a closed container, when water is heated, the pressure increases. Water and vapour will be in equilibrium at the same temperature. With no place to escape, if heat is applied to the closed container, the velocity of the molecules in the gas state will increase, hence temperature. This will increase the pressure on the surface of the liquid. And, the temperature of the water system will then increase. There are two important parts. The rubber ring prevents air from escaping. If it did, the pressure wouldn’t build up. The other important part is the valve on top. It is designed to ensure that pressure doesn’t build up to dangerous levels inside the cooker. If it does, the cooker can explode.

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