2.2b KCL

Kirchhoff's Current Law

Kirchhoff’s current law (KCL) states that net current flowing out of (or into) any node must equal zero.

\usepackage[straightvoltages]{circuitikz}
\begin{document}
\begin{circuitikz}
\draw
(-2.2,0) to[generic, v^=$i_1$] (0,0)
to [generic, v^=$i_2$] (2.2,0)
(0,-2.2) to[generic, v=$i_3$] (0,0);
\end{circuitikz}
\end{document}

In other words,
$$i_1-i_2+i_3=0,$$
where $i_2$ is flowing out of the node and is therefore subracted.