Question

In a P-V graph if the initial state is further away from the y axis than the final state, which of these statements is true?

• A. The work done by the gas is positive
• B. The work done by the gas is zero
• C. The work done by the gas is negative
• D. No generalized statement can be made

Answer 1

The correct option is C

The work done by the gas is negative

Whenever the initial state is further away from the y axis than the final state, the initial volume would be higher than final volume.

Let us consider that this process happens on the system shown in the figure below


When the piston is moving from the initial position (higher volume) to the final position (lower volume) it moves in the direction opposite to that of the force $F_g$ applied by the gas on it ($F_g$ = pressure of gas $\times$ area).
Since the displacement and force are opposite to each other, the work done by the gas will be negative.