Question

In an isothermal process the volume of an ideal gas is halved. One can say that

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

Answer 1

Answer: (C)

Work done by the gas is negative

Answer 2

For isothermal process

$dU = 0$and work done $= dW = P(V_{2} - V_{1})$

$\because\mspace{6mu} V_{2} = \frac{V_{1}}{2} = \frac{V}{2}$∴ $dW = - \frac{PV}{2}$