In a cyclic process shown in the figure on ideal gas is adiabatically taken from B to A, the work done on the gas during the process `B rarr A` is 30J, when the gas is taken from `A rarr B` the heat absorbed by the gas is 20J. What is the change in internal ebergy of the gas in the process `A rarr B`.

Explanation

`W_(BA)= -30J,Q_(BA) = 0`
`:. Delta U_(BA) = -W_(BA) = 30J`
In a cyclic process `DeltaU=0`
Now, `Delta U_(AB) = -Delta U_(BA) = -30J`