applying first law of thermodynamics obtain an adiabatic relation between pressure and volume.

Dear student

 

A/C to 1st law of thermodynamics;

 



dQ= dU + PdV

For adiabatic process, dQ=0

So, dU + PdV=0

or, dU = -PdV

When the expansion takes place, volume of the gas increases i.e. dV = +ve, hence dU = -ve

;

i.e. internal energy of the gas decreases and hence the temperature falls.

If the gas is compressed, volume of the gas decreases, i.e. dV = -ve, hence dU = +ve; i.e.

internal energy of the gas increase and hencew its temperature increase.

Hope this clarifies your doubt.

Regards

Team

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