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Mechanical Properties Of Fluids

Question
CBSEENPH11019648

Derive the equation of state for adiabatic process. Plot P versus V graph for the process.

Solution
According to the first law of thermodynamics,
                     dQ space equals space dU plus dW 
In an adiabatic process, no heat is allowed to exchange between the system and surrounding, therefore dQ = 0.
Thus, 
space space space space space space space dU space plus space PdV space equals space 0 space

rightwards double arrow space straight C subscript straight P dT space plus space PdV space equals space 0 space
rightwards double arrow space straight C subscript straight V dT space plus space PdV space equals space 0 space

That space is comma space

straight C subscript straight V dT space plus space RT over straight V dV space equals space 0 space left square bracket because space PV space equals space RT right square bracket space

That space is comma space

dT over straight T plus straight R over straight C subscript straight p dV over straight V space equals space 0 space

rightwards double arrow space dT over straight T space plus space left parenthesis straight gamma space minus 1 right parenthesis space dV over straight V space equals space 0 space

On space integrating comma space

space space space space integral dT over straight T space plus space space left parenthesis straight gamma space minus 1 right parenthesis space integral dV over straight V space equals space constant

rightwards double arrow space Ln space straight T space plus space space left parenthesis straight gamma space minus 1 right parenthesis space Ln space straight V space equals space constant

rightwards double arrow space TV to the power of straight gamma space minus space 1 end exponent space equals space constant space comma space which space is space
the space equation space of space state. space

Since comma space PV space equals space space RT space

we space have comma space straight T space equals space PV over straight R space

therefore space TV to the power of straight gamma space minus space 1 end exponent space equals space PV over straight R straight V to the power of straight gamma space minus space 1 end exponent space equals space constant

rightwards double arrow space PV to the power of straight gamma space equals space constant
P vs. V graph for an adiabatic process is as shown below.