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

**The reason for C _{p} greater than C_{v} 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 C _{p}=dU+P.dV**

**And C _{v}=dU**

**Therefore using the above relation C _{p} is greater than C_{v}.**

**Physical Meaning of why C _{p} is greater than C_{v}:**

**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 C _{p} has a greater value than C_{v}.**

**Hope it helps!!**

**Cheers!!**

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