Kirchhoff’s Second Law | 基尔霍夫第二定律

📚 Kirchhoff’s Second Law | 基尔霍夫第二定律

Kirchhoff’s second law is a fundamental circuit rule that follows directly from conservation of energy. It is sometimes called the loop rule or Kirchhoff’s voltage law (KVL). For any closed loop in a circuit, the total energy gained per unit charge by the moving charges must equal the total energy lost per unit charge. This article explains the law, its sign conventions, worked examples, and common exam pitfalls for CIE A-Level Physics.

基尔霍夫第二定律是一条由能量守恒直接推出的基本电路定律，也称为回路规则或基尔霍夫电压定律(KVL)。对于电路中任意闭合回路，运动电荷每单位电荷获得的总能量必定等于每单位电荷失去的总能量。本文讲解该定律、符号约定、例题以及 CIE A-Level 物理考试中的常见失分点。

1. Statement of the Law | 定律表述

Around any closed loop in a circuit, the algebraic sum of the electromotive forces (e.m.f.s) is equal to the algebraic sum of the potential differences across the components.

在电路中，沿任意闭合回路，电动势(e.m.f.)的代数和等于各元件两端电势差的代数和。

Σ ε = Σ IR

An equivalent form is that the sum of all

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