Question

why food is cooked fast in pressure cooker then in vessel

Answer 1

Water boils at higher temperatures under pressure so, food cooks at a higher temperature. Pressure cookers are more common in the mountains where elevation is higher. At higher elevations, atmospheric pressure is lower and therefore water boils are lower temperatures. In order to make up for that difference, people use pressure cookers. This higher temperature is why it is so important to let a pressure cooker cool and take caution when opening it. Pressure cookers are able to reach significantly higher temperatures which can cause serious injury if the pot opened when it is still too hot.