Circuitikz: polar capacitor terminals polarity labels are wrong

Question

When using circuitikz to draw some circuit pictures, I noticed that the terminal polarity labels are incorrect (I believe) for polar capacitors. Consider the following:

\documentclass{article}
\usepackage[american voltages,siunitx]{circuitikz}

\begin{document}
\begin{circuitikz}
   \draw (0,0) to [battery=\SI{9}{V}] (3,0)
               to [pC,v=$v_C$] (6,0);
\end{circuitikz}
\end{document}

When I compile this (circuitikz v2.4) I get the following picture:

I believe that the rounded terminal should be the negative one and the straight terminal is the positive one. Am I missing anything?

Please forgive me if this is not the right place to post this. I noticed that the package author sometimes posts here, and so I thought that this might be appropriate, and also perhaps I'm not understanding something!

Answer 1

I am not quite sure what you are asking.

If you want to change rounded terminal's polarity always:

 \draw (0,0) to [battery=\SI{9}{V}] (3,0)
               to [pC,v^>=$v_C$] (6,0); %<--- change v= to v^>=

But if you want to change the polarity, then reverse the co-ordinates like this:

\documentclass{article}
\usepackage[american voltages,siunitx]{circuitikz}

\begin{document}
\begin{circuitikz}
  \draw (0,0) to  [battery=\SI{9}{V}] (3,0) ;
  \draw (6,0) to  [pC, v=$v_C$] (3,0) ; % <-----------co-ordinates reversed here
\end{circuitikz}
\end{document}

Answer 2

I believe that it has everything to do with the direction of the greater than(>) or less than (<) symbol. In the case of CircuiTikZ, these inequalities are essentially the head of the arrow, pointing in the direction of the positive terminal—at least for bipolar elements, I'm uncertain about tripolar elements.

Notice that the only [non-textual] difference in the following code occurs in that single character:

\begin{circuitikz}[american voltages]
   \draw (0,0) to [battery, i=$$, v_>=$Potential\;increases$] (2.25,0);
\end{circuitikz}

\begin{circuitikz}[american voltages]
   \draw (0,0) to [battery, i=$$, v_<=$Potential\;decreases$] (2.25,0);
\end{circuitikz}

The workaround you discovered with the coordinates may work, I would suggest avoiding it—especially as your circuits increase in complexity.