📚 IGCSE Edexcel Physics: Circuit Analysis Key Points | IGCSE Edexcel 物理：电路分析 考点精讲
Circuit analysis forms a core part of the IGCSE Edexcel Physics syllabus. Understanding how to interpret circuit diagrams, apply fundamental laws, and analyse both series and parallel circuits is essential for examinations and practical work. This revision guide covers all the key concepts, from basic definitions to component behaviour and safety, equipping you with the knowledge needed to tackle circuit problems confidently.
电路分析是IGCSE Edexcel物理课程的核心部分。理解如何解读电路图、应用基本定律并分析串联和并联电路，对于考试和实践都至关重要。这份复习指南涵盖了从基本定义到元件行为和安全的所有关键概念，为你提供自信应对电路问题所需的知识。
1. Circuit Symbols and Diagrams | 电路符号与电路图
Recognising standard circuit symbols is the first step in analysing circuits. The Edexcel specification requires you to draw and interpret common components.
识别标准电路符号是分析电路的第一步。Edexcel课程要求你会画并解释常见元件。
A cell (power supply) provides electrical energy; symbol: long line (positive) and short line (negative).
电池（电源）提供电能；符号：长线（正极）和短线（负极）。
A battery consists of two or more cells; shown as repeated long and short lines.
电池组由两个或多个电池组成；表示为重复的长短线。
A fixed resistor limits current; symbol: a rectangle.
固定电阻限制电流；符号：矩形。
A variable resistor (rheostat) can change resistance; symbol: a rectangle with a diagonal arrow.
可变电阻器（滑动变阻器）可以改变电阻；符号：带有对角箭头的矩形。
A thermistor has resistance that decreases as temperature increases; symbol: resistor with a line through it, often annotated 't°'.
热敏电阻的电阻随温度升高而降低；符号：带有一条线的电阻，常标注 't°'。
A light-dependent resistor (LDR) has resistance that decreases in bright light; symbol: circle inside a rectangle with arrows pointing towards it.
光敏电阻（LDR）电阻在强光下降低；符号：矩形中的圆圈，周围有箭头指向它。
A diode allows current to flow in one direction only; symbol: triangle pointing to a line.
二极管只允许电流单向流动；符号：指向一条线的三角形。
A light-emitting diode (LED) emits light when current flows; symbol: diode symbol with arrows pointing away.
发光二极管（LED）在电流流过时发光；符号：带有指向外侧箭头的二极管符号。
A fuse protects circuits from high current; symbol: rectangle with a wire passing through.
保险丝保护电路免受大电流损坏；符号：有导线穿过的矩形。
A voltmeter measures voltage and is connected in parallel; symbol: circle with 'V'.
电压表测量电压，并联连接；符号：带有 'V' 的圆圈。
An ammeter measures current and is connected in series; symbol: circle with 'A'.
电流表测量电流，串联连接；符号：带有 'A' 的圆圈。
2. Current, Voltage, and Resistance | 电流、电压和电阻
mperes (A). One ampere equals one coulomb of charge passing a point per second: I = Q / t.
电流（I）是电荷流动的速率。它以安培（A）为单位。1安培等于每秒通过某点的电荷为1库仑：I = Q / t。
Current flows from the positive terminal to the negative terminal in conventional current, but electrons actually move in the opposite direction.
在传统电流方向中，电流从正极流向负极，但电子实际上向相反方向移动。
Voltage (V), also called potential difference, is the energy transferred per unit charge. It is measured in volts (V). A voltmeter is always connected in parallel across a component.
电压（V），也称电势差，是每单位电荷转移的能量。它以伏特（V）为单位。电压表始终并联在元件两端。
poses the flow of current. It is measured in ohms (Ω). Resistance is defined by R = V / I.
电阻（R）衡量元件对电流流动的阻碍程度。它以欧姆（Ω）为单位。电阻由 R = V / I 定义。
3. Ohm's Law | 欧姆定律
Ohm's law states that the current through a conductor is directly proportional to the potential difference across it, provided the temperature remains constant.
欧姆定律指出，在温度保持不变的条件下，流过导体的电流与导体两端的电势差成正比。
V = I × R
An ohmic conductor (e.g., a metal wire at constant temperature) has a constant resistance. Its I–V graph is a straight line through the origin.
欧姆导体（例如恒温下的金属导线）电阻恒定。其 I–V 图是一条过原点的直线。
Non-ohmic components, such as filament lamps and diodes, do not obey Ohm's law because their resistance changes with current.
非欧姆元件（例如灯丝灯泡和二极管）不遵守欧姆定律，因为它们的电阻随电流变化。
For a fixed resistor, doubling the voltage doubles the current, giving a linear relationship.
对于固定电阻，电压加倍则电流加倍，呈线性关系。
4. Series Circuits | 串联电路
Components are connected end-to-end in a single loop. There is only one path for current to flow.
元件首尾相连形成单一回路。电流只有一条路径。
The current is the same at all points in a series circuit: Iₜ = I₁ = I₂ = I₃ ...
串联电路中各点的电流相等：Iₜ = I₁ = I₂ = I₃ ...
otal voltage from the power supply is shared between the components: Vₜ = V₁ + V₂ + V₃ ...
电源总电压由各元件分担：Vₜ = V₁ + V₂ + V₃ ...
ces: Rₜ = R₁ + R₂ + R₃ ... Adding more resistors in series increases the total resistance.
总电阻是各电阻之和：Rₜ = R₁ + R₂ +
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