Question

We consider a thermodynamic system. If $\Delta U$ represents the increase in its internal energy and $W$ the work done by the system, which of the following statements is true?

• A. $\Delta U=-W$ in an adiabatic process
• B. $\Delta U=W$ in an isothermal process
• C. $\Delta U=-W$ in an isothermal process
• D. $\Delta U=W$ in an adiabatic process

Answer 1

Answer: (A)

According to the first law of thermodynamics
$\Delta Q=\Delta U+\Delta W$
In adiabatic process $\Delta Q=0$, hence $d U=-dW$