The Physics of Pressure Cooker

The Physics of the Pressure Cooker

Generally, water boils at 100 degree Celsius (212 degree Fahrenheit) in normal room temperature and pressure. If somebody boils the water for five minutes or for twenty minutes, the temperature will always remain the same. The pressure of air affects the boiling point of water. If air pressure is changed, then the boiling point will also change according to it (How does”).

This is why a pressure cooker cooks food quickly as the pressure of the steam in the cooker gets as high as twice the normal pressure of the atmosphere. A this pressure, water gets boils at 120 degree centigrade (“Foundation”).

Before defining the term pressure cooker, we have to know, what is pressure? Pressure is the force acted per unit area exerted on a surface. In SI unit, it is measured in newton per square meter. It is called Pascal (Pa). The air pressure at the earth’s surface is due to the weight of the column of air above the surface (Kirkpatrick L.D 171)

Simply, a pressure cooker is a sealed cooking pot where water vapor cannot escape to the atmosphere. Since, water vapor cannot escape to the atmosphere at the boiling point, 100 degree centigrade; it results in the increase in pressure and temperature. That is why food cooks faster in a pressure cooker. To work with a pressure cooker is a risky job. If the pressure inside the pressure cooker could not move out, then the whole pot may blow up. That is why all pressure cookers have pressure release valves. These cookers are typically used at higher altitudes where water boils at a temperature which is too low to enable complete cooking. To understand fully the relationship between temperature, pressure and volume people need to have knowledge about the...

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Kirkpatrick, D. L., Wheeler, F.G. Physics a World View. Harcourt, Inc., 2001. “History of the Pressure Cooker?” 21 Mar. 2003 <http://missvickie.com/library/ history.html>.

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<http://cherwell.oxon.sch.uk/prm/hfact5.htm “View Question” 21 Mar. 2004 <http://www.science.ca/askascientist/viewquestion.php? qID=100>.