Kirchhoff’s Rules

Core Sentence / 核心句

Kirchhoff’s junction rule expresses charge conservation, and the loop rule expresses energy conservation.

中文理解：节点定律保证节点不持续积累电荷；回路定律保证绕闭合路径一圈后电势升降代数和为零。

\sum I_{in} = \sum I_{out}

或统一 signed convention：

\sum I_{k} = 0

\sum Δ V = 0

sign table：

branch current 可任意设方向。解得 negative value，只表示真实方向与假设相反。

connected network with $N$ essential nodes and $B$ branches：

N - 1 independent junction equations

B - N + 1 independent loop equations

看到 multiple loops、multiple sources、bridge network、unknown branch currents、not reducible by series/parallel inspection，就使用 Kirchhoff’s rules。