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

Options

A. In process `CA` change in internal energy is `225R`.
B. In process `AB` change in internal energy is `-150R`.
C. In process `BC` change in internal energy is `-225R`.
D. Change in internal energy during the whole cyclic process is `+150R`.

Answer

C

Explanation

`DeltaU_(CA) = nC_(V)(T_(A)-T_(C))`
=`1xx(3)/(2)R xx (300-450) = (-225 R)`
`DeltaU_(BC) = nCv(T_(C)-T_(B))`
= ` 1 xx (3)/(2)R xx (450 - 600) = -225R`
`DeltaU_(ABCA) = DeltaU_(CA) + DeltaU_(AB) + Delta_(BC) = 0`