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

Answer 1

The correct option is A

$\Delta U=-W\text{in an adiabatic process}$
According to the first law of thermodynamics,
$Q=\Delta U+W$
In adiabatic process,
$Q=0$
Hence,
$\Delta U=-W$
Therefore option $\left(a\right)$ is correct
For isothermal process,
$\Delta U=0$
Hence option $\left(b\right)$ and $\left(c\right)$ are wrong