11.Thermodynamics
easy

One mole of a diatomic ideal gas undergoes a cyclic process $ABC$ as shown in figure. The process $BC$ is adiabatic. The temperatures at $A, B$ and $C$ are $400\ K, 800\ K $ and $600\ K$ respectively. Choose the correct statement

A

The change in internal energy in the process $CA$ is $700\ R$

B

The change in internal energy in the process $AB$ is $ -350R$

C

The change in internal energy in the process $BC$ is $-500R$ 

D

The change in internal energy in whole cyclic process is $250R $ 

(JEE MAIN-2014)

Solution

In cyclic process, change in total internal energy is zero.

$\Delta {U_{cyclic}} = 0$

$\Delta {U_{BC}} = n{C_v}\Delta T = 1 \times \frac{{5R}}{2}\Delta T$

$Where,{C_v} = molar\,specific\,heat\,at\,constant\,volume.$

$For\,BC,\Delta T =  – 200K$

$\therefore \,\,\Delta {U_{BC}} =  – 500R$

Standard 11
Physics

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