Question

When a system is taken through the process abc shown in figure, 80 J of heat is absorbed by the system and 30 J of work is done by it. If the system does 10 J of work during the process adc, how much heat flows into it during the process ?

Answer 1

$\Delta \text{Q}=\Delta \text{U}+\Delta \text{W}$

In abc, $\Delta \text{Q}=80\text{J},\Delta \text{W}=30\text{J}$

So, $\Delta \text{U}=(80-30)\text{J}=50\text{J}$

Now in abc,

$\Delta \text{W}=10\text{J}$

So, $\Delta \text{Q}=10\text{J}+50\text{J}=60\text{J}$ $[\therefore \Delta \text{U}=50\text{J}]$