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. infernal 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)

In an isothermal process, work done is
$dW=pdV$
$\therefore dW=p\left(V_2-V\right)$
$=p\left(\frac{V}{2}-V\right)$
$\left(\because V_1=V,V_2=\frac{V}{2}\right)$
$=-\frac{pV}{2}$
So, the work done by the gas is negative.