Question

There is an expansion of a gas in a thermodynamic system. But this change cannot be plotted on a P-V diagram. Then it is

• A. an isothermal expansion.
• B. a free expansion
• C. an adiabatic expansion
• D. an isobaric expansion

Hint:

Only quasi-static processes pass through equilibrium states and can be drawn. One expansion is sudden and uncontrolled.

Answer 1

The Correct Option is B

Step 1: Elimination
Isothermal ($PV=\text{constant}$), adiabatic ($PV^{\gamma}=\text{constant}$) and isobaric ($P=\text{constant}$) processes all have definite curves.

Step 2: Remaining option
Free expansion occurs rapidly against zero pressure, with no equilibrium state in between.

Step 3: Result
Only the free expansion cannot be drawn.

Final Answer:
Only a free expansion has no path on the P-V diagram. \[ \boxed{\text{(B) }\text{a free expansion}} \]