how does a pressure cooker work?

Answer 1

stolen from wiki

Pressure cooking is a method of cooking in a sealed vessel that does not permit air or liquids to escape below a preset pressure. Because water's boiling point increases as the pressure increases, the pressure built up inside the cooker allows the liquid in the pot to rise to a temperature higher than 100 °C (212 °F) before boiling.

Answer 2

A home pressure cooker generally raises the pressure to about 15psig. (2 atmospheres)
At this pressure water boils at around 250°F (121°C).

The added heat allows food to cook in about half the normal time as for 212°F (100°C).
The water level in the cooker is only 1 to 2 inches (2½ to 5cms). The food is in separate containers within the cooker resting on the trivet and they are cooked by the high pressure, superheated steam.
The pressure is controlled by a weight placed in the top of the lid and is so constructed as to lift at the correct pressure and vent excess steam from the cooker, thus controlling the pressure. When the weight is passing steam from the cooker, the heat can be reduced until just a faint 'Hiss' is coming from the escaping steam.
The lid has a seal ring to prevent leakage of steam.
The faster cooking time decreases the amount of energy used in the cooking process. (Saves gas or electricity).
Before opening the lid, be sure to cool the cooker by allowing cold water to run over it, or allowing the pressure to drop sufficiently to enable the lid to be removed SAFELY.
If this is not done, removing the lid with full pressure on the lid will be very dangerous with the possibility of serious burns.

Answer 3

How Does Pressure Cooker Work

Answer 4

And the amount of pressure built up inside in household pressure cookers is determined by the weight placed on the steam exit tube. When the water is brought to a boil and the weight starts rocking, there is enough steam pressure inside to slightly lift the weight which tips to one side, opening more gap and letting pressure fall. The heat is reduced so the weight gently rocks.
The higher pressure raises the boiling point of water, permitting faster cooking. At higher altitudes, where the lower pressure lowers the boiling point so far as to extend cooking times, using a pressure cooker permits more practical cooking times.

Answer 5

Just to add to the prior good answers, that it is not just the higher temperature of the steam under pressure that aids in the cooking - heat transfer to what is beng cooked, but the nature of steam to condense on a cooler surface, transfering its heat in the process. Any part being cooked that is not up to temperature yet, the steam condenses on, heating it, and drawing in more steam until everything is equilibrated hot.

Answer 6

http://missvickie.com/workshop/howdoesit.html

http://fastcooking.ca/pressure_cookers/how_pressure_cookers_work.php