Question

A gas can be taken from $A$ to $B$ via two different processes $ACB$ and $ADB$. When path $ACB$ is used $60J$ of heat flows into the system and $30J$ of work is done by the system. If path $ADB$ is used work done by the system is $10J$. The heat Flow into the system in path $ADB$ is :

• A. $80J$
• B. $20J$
• C. $100J$
• D. $40J$

Answer 1

The correct option is D $40J$

$\Delta Q_{ACB}=\Delta W_{ACB}+\Delta U_{ACB}$
$\Rightarrow 60J=30J+\Delta U_{ACB}$
$\Rightarrow \Delta U_{ACB}=30J$
$\Rightarrow \Delta U_{ADB}=\Delta U_{ACB}=30J$
$\Delta Q_{ACD}=\Delta U_{ACB}+\Delta W_{ADB}$
$=10J+30J=40J$