A system goes from P to Q by two different paths in the P -V diagram as shown in figure. Heat given to the system in path 1 is 1000 J. The work done by the system along path 1 is more than path 2 by 100 J. What is the heat exchanged by the system in path 2 ?

Explanation

For path 1: Heat given `Q_1`=+1000 J
Work done = `W_1`
For path 2: Work done `W_2=W_1-100J`
Heat given `Q_2`= ?
As change in internal energy between two states for different path is same.
`therefore DeltaU=Q_1-W_1=Q_2-W_2`
`therefore 1000-W_1=Q_2-(W_1-100)`
`therefore Q_2=1000-W_1+W_1-100`
`therefore Q_2`=900 J