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Thermal Physics Work Done During a Change of Volume of a Gas Consider a quantity of gas in a container which has a frictionless piston as shown in the diagram below. The volume occupied by the gas is changed by DV.
The pressure, p, acting on the surface of the piston produces a force, F, equal to pA. During the change in volume, this force does some work. The work done by this force is w = Fs = pAs but As is the change in the volume occupied by the gas, DV. Therefore
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The above result shows that if the
temperature of a gas is increased at
constant volume, no work
is done. For this reason, gases are said to have two principal specific (or molar) heat capacities:
It should be clear that cp > cv and that the difference between them is given by
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© David Hoult 2008 |
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