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explain why cp is always greater than cv????

BEST ANSWER Certified by MeritNation Expert

The reason for Cp greater than Cv is very simple.

This can be easily demonstrated by First law of thermodynamics.

At constant Pressure

dQ=dU+P.dV----(1)

Where as,

At Constant Volume,

dQ=dU+P.dV

Since dV=0

Therefore dQ=dU     ---(2).

Therefore Cp=dU+P.dV

And Cv=dU

Therefore using the above relation Cp is greater than Cv.

Physical Meaning of why Cp is greater than Cv:

At constant volume, heat is required only to increase the internal energy of system while At constant Pressure heat is needed for increasing Internal energy as well as for doing the work to displace the piston of system through a distance. Therefore Cp has a greater value than Cv.

Hope it helps!!

Cheers!!

Posted by Devilishly Cool(KENDRIYA VIDYALAYA NO 2) on 8/12/13

This conversation is already closed by Expert

thanx dude.. a thumbs up frm mah side.. :)

Posted by Angel Malik(OXFORD ACADEMY RUDRAPUR) on 8/3/12

explain why air temperature reading are always taken with thermometer in the shade?

Posted by Kamalbistaon 5/12/12

The air temperature reading is always taken in shade because due to the exposure of sunlight thermometer reading increases than the real temperature.

Posted by Pavithraon 5/12/13

I need a thumbs up.