The p–V diagram (A-level only) Flashcards – AQA A-level Physics (7408)

Which quantities are plotted on the axes of a pressure–volume diagram?

Pressure $p$ on the vertical axis and volume $V$ on the horizontal axis.

What do a point and a path represent on a pressure–volume diagram?

A point represents a state; a path represents a process in which pressure and volume change.

How does the direction of a path on a pressure–volume diagram indicate expansion or compression?

Moving toward greater volume indicates expansion; moving toward smaller volume indicates compression.

What area on a pressure–volume diagram represents the work done by the system during a volume change?

The area between the process curve and the volume axis over that change.

What is the sign of work done by a system during expansion and during compression?

Positive during expansion; negative during compression.

What is the work done by a system during a constant-pressure volume change?

$W=p\Delta V=p(V_{\text{final}}-V_{\text{initial}})$

What does a cyclic process look like on a pressure–volume diagram?

A closed loop: the system returns to its initial state.

What represents the magnitude of the net work done in one cycle on a pressure–volume diagram?

The area enclosed by the loop.

How does the direction of a cycle on a pressure–volume diagram determine the sign of net work done by the system?

Clockwise: positive net work. Anticlockwise: negative net work.