Line
Definition
... a linear process according to
$$ p = a V + b $$
, denoted by a line on the pV diagram.
Where it occurs.
... in piston-cylinder-spring problems.
Special features
In expansion, note that there should be increases in p, V and T.
How to draw it
The POI is connected to the most recently drawn symbol. Plot a symbol at the line's start point, pick a POI at the end point and press the line button.
The theory
On the pV plot, work is area under the line. Given that said area is a trapezium,
$$ W= - p_{avg} (V_2-V_1) $$
where \( p_{avg} = (p_1+p_2)/2 \).