Function of pressure cooker?

cook things at high temperatures. thats the function of it.

yes - you can get the water to go to a higher temp whilst cooking due to the higher pressure - Thus a faster cook.

it's function = reduce cooking time.

 

At 2 bars, the boiling temperature of water is already 120 deg C.

 

http://www.efunda.com/materials/water/steamtable_sat.cfm

I used an old one as a low pressure air receiver.

Except its use as a method of cooking, it's also used to reduce food toxins.

And for killing bacteria etc.

yah, thats true ,pressure cooker's functions is cooking.and it also lowers the time of cooking and how? But what is the mechanism going during this operation?

So, we've established that the temperature inside a pressure cooker is higher.

 

See it like this: the higher the temperature, the faster molecules are moving. This also goes for the water inside the cooker. So, at 120 deg C, the molecules move faster than in your normal pan. This means that they also penetrate the rice/pasta faster. The food is finished when enough water has entered the food. The faster the water molecules move, the faster this is finished.

 

For potatoes, there is simply the need to warm up. This obviously goes faster at higher temperature.

Function of pressure cooker?

 

To decrease cooking times, via increasing the boiling point of water and hence the temperature that the food is cooked. Note that at high altitudes, this can be used to counter the effects of the lower pressure that can result in insane cooking time.