Explain the free expansion of gas. - Vidyadip

Question

Explain the free expansion of gas.

✓

Answer

The expansion of gas in vacuum is known as free expansion of gas. In free expansion of ideal gas there is no work done.
According to first law of thermodynamics :
$
\begin{array}{l}
\Delta U=q+w \\
\left(w=-p_{e x} \Delta V\right)
\end{array}
$
On putting value of w
$
\Delta U=q-p_{cx} \Delta V
$
For isochoric process : $\Delta V =0$
Hence $\quad \Delta U=q_v$
The free and isothermal expansion of an ideal gas can be done in vacuum than ( $T =$ constant), so $w=0$ because $p _{ ex }=0$. Joule do experiments and concluded if $q =0$ then $\Delta U =0$.

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