Question

A system is changed from state A to state B by one path and from B to A by another path. If $△U_1$ and $△U_2$ are the corresponding changes in internal energy, then:-

• A. $△U_1+U_2=+ve$
• B. $△U_1+U_2=-ve$
• C. $△U_1+U_2=0$
• D. None of the above

Answer 1

The correct option is C $△U_1+U_2=0$

The system is going from A to B $\left(△U_1\right)$ and then B to A $\left(△U_2\right)$
As the initial and final states are same, and we know internal energy is a state function.
So,
$\Delta U_{total}=0$
This means,
$△U_1+U_2=0$