words per minute
11
ASHEESH_SINGH
00:00
Speed
When a body of air is subjected to an increase in pressure it undergoes compressional heating as opposed to thermal heating. If the same body of air is subjected to a reduction in pressure it undergoes expansional cooling as opposed to thermal cooling. Changes of this type are called adiabatic changes. For example in the former case, the temperature of the air in a bicycle pump is increased when vigorously compressed. In the latter case, when compressed gas is released from a cylinder its temperature falles. Atmospheric pressure decreases with height. Thus, if a body of air rises through the surrounding air (ie its environment) it undergoes a reduction in pressure and is cooled adiabatically. In both cases, no interchange of heat take place between the body of air and its environment.