Question

If in an isothermal process the volume of ideal gas is halved, then we can say that :

• A. Internal energy of the system decreases
• B. Internal energy of the system increases
• C. Work done by the gas is negative
• D. Work done by the gas is positive

Answer 1

Answer: (C)

Work done by the gas is negative

In an isothermal process, work done is

$dW=pdV$

$\therefore dW=p(V_2-V_1)$

$=p(\frac{V}{2}-V)$ $(\because V_1=V,V_2=\frac{V}{2})$

$=-\frac{pV}{2}$

So, the work done by the gas is negative.