Question

The pressure of a gas changes linearly with volume from 10 kPa, 200 cc to 50 kPa, 50 cc.
(a) Calculate the work done by the gas.
(b) If no heat is supplied or extracted from the gas, what is the changes in the internal energy of the gas?

Answer 1

First draw `P-V` diagram
(a) `DeltaW_(1rarr2)=`area below `1rarr2`
`=-(1)/(2)(10+50)xx10^3xx(200-50)xx10^-6`
`=-4.5J`
(b) From `I^(st)` law, `DeltaQ=DeltaU+DeltaW`
`0=DeltaU-4.5`
`DeltaU=4.5J`