One mole of a 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 600K respectively. Choose the correct statement:

Options

A. change in internal energy in the process AB `=350R`
B. change in internal energy in the process BC is `-500R`
C. change in internal energy in the whole cyclic process is `250R`
D. change in internal energy in the process CA is `700R`

Answer

B

Explanation

`DeltaU_(AB)=nC_(v)(T_(B)-T_(A))`
`=1xx(5R)/2(800-400)=1000R`
`DeltaU_(BC)= n C_(v)(T_(c)-T_(B))`
`= 1xx(5R)/2(600-800)= -500R`
`DeltaU_(total)=0 ( :. "Process is cyclic")`
`DeltaU_(CA)= n C_(v)(T_(A)-T_(C))`
`= 1xx(5R)/2(400-600)= -500R`