Question

During isothermal expansion of an ideal gas, its internal energy?

• A. Decreases
• B. Increases
• C. May increase or decrease
• D. Remains unchanged

Answer 1

The correct option is D Remains unchanged

isothermal expansion

$w<0$ (as vol. T)

$\Delta U=n{C}_U\Delta T$ (for ideal gas)

$=0$

as $\Delta T=0$

$\therefore$ internal energy is same.