Question

One mole of 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 whole cyclic process is 250 R
• B. The change in internal energy in the process CA is 700 R
• C. The change in internal energy in the process AB is - 350 R
• D. The change in internal energy in the process BC is - 500 R

Answer 1

Answer: (D)

$\Delta U=n C_{V} \Delta T=1 \times \frac{5 R}{2} \Delta \,T$
For $BC, \Delta T=-200 K$
$\Rightarrow \,\Delta U=-500 \,R$