PV diagrams

Some basic PV (pressure-volume) diagrams with isothermal, isochoric, isobaric or adiabatic processes, including the Otto cycle and Carnot cycle. For more figures related to thermodynamics, see the “thermodynamics” category.

PV diagram for a constant pressure P:
PV diagram for a constant volume V:
PV diagram with an isotherm (constant temperature T):
PV diagram of a simple, engine:
Connecting isotherms via different paths in PV by adding heat Q to the system:
Specific heat capacities for constant pressure (C_P) or constant volume (C_V):
Connecting isotherms with an adiabatic process:
The work done by an adiabatic process is given by the area:
PV diagram for the Otto cycle:
PV diagram for the Carnot cycle:

Edit and compile if you like:

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% Author: Izaak Neutelings (June, 2018)
\documentclass[border=3pt,tikz]{standalone}
\usepackage{tikz}
\usepackage{amsmath} % for \text
\usepackage[outline]{contour} % glow around text
\usetikzlibrary{arrows.meta} % to control arrow size
\tikzset{>={Latex[length=4,width=4]}} % for LaTeX arrow head
\usetikzlibrary{calc,decorations.markings,arrows.meta}
\usepackage{xcolor} % for colored text
\contourlength{1.2pt}
\colorlet{mylightblue}{blue!20}
\colorlet{myblue}{blue!80!black}
\colorlet{mydarkblue}{blue!30!black}
\colorlet{mylightred}{red!10}
\colorlet{myred}{red!80!black}
\colorlet{mydarkred}{red!60!black}
\colorlet{mydarkgreen}{green!30!black}
%\tikzstyle{midarr}=[decoration={markings,mark=at position 0.5 with {\arrow{stealth}}},postaction={decorate}]
\tikzset{
  midarr/.style={decoration={markings,mark=at position #1 with {\arrow{stealth}}},postaction={decorate}},
  midarr/.default=0.5
}
\def\xtick#1#2{\draw[thick] (#1)++(0,.1) --++ (0,-.2) node[below=-.5pt,scale=0.9] {#2};}
\def\ytick#1#2{\draw[thick] (#1)++(.1,0) --++ (-.2,0) node[left=-.5pt,scale=0.9] {#2};}
\begin{document}
% PV diagram - constant P
\def\N{40} % number of plot samples
\def\xmax{3}
\def\ymax{2.5}
\begin{tikzpicture}
  
  % AREA
  \coordinate (A) at (.2*\xmax,.8*\ymax);
  \coordinate (B) at (.8*\xmax,.8*\ymax);
  \coordinate (C) at (.8*\xmax,.2*\ymax);
 
 
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