Q. The internal energy of an ideal gas increases during an isothermal process when the gas is
A) Expanded by adding more molecules to it
B) Expanded by adding more heat to it
C) Expanded against zero pressure
D) None of these
Explanation
(a) Internal energy of an ideal gas is given by
$U = \frac{f}{2}\mu RT = \frac{f}{2}\left( \frac{N}{N_{A}} \right)RT \Rightarrow U \propto NT$
In isothermal process $T =$ constant $\Rightarrow U \propto N$
$i.e.$ internal energy increases by increasing number of molecules ($N$)
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.