📚 Edexcel A-Level Physics Combined 200: Core Topics and Exam Strategy | Edexcel A-Level 物理综合 200：核心主题与应试策略
This article brings together the most frequently examined ideas in Edexcel A-Level Physics under a single 'Combined 200' revision framework. It is designed for students who have finished the main syllabus and need to practise mixed-topic questions, where mechanics, electricity, fields, waves and quantum ideas appear side by side.
本文把 Edexcel A-Level 物理考试中最常出现的知识点整合在一个 "综合 200" 复习框架下。它适合已经完成主体课程、需要训练混合章节题目的学生，这些题目往往同时涉及力学、电学、场、波动和量子概念。
1. Mechanics: SUVAT and Newton's Laws | 力学：SUVAT 与牛顿定律
In Edexcel A-Level Physics, the SUVAT equations only apply when acceleration is constant. You must define the positive direction clearly before substituting values.
在 Edexcel A-Level 物理中，SUVAT 方程只适用于加速度恒定的情况。代入数值前必须先明确规定正方向。
v = u + at, s = ut + ½at², v² = u² + 2as
y is constant, while the vertical motion obeys the same equations with a = g = 9.81 m s⁻².
对于抛体运动，要把问题分解为水平和竖直分量。水平速度保持不变，竖直运动遵循相同的方程，其中 a = g = 9.81 m s⁻²。
Newton' ass it reduces to F = ma. Remember to use the resultant force, not just one applied force.
牛顿第二定律最准确的表述是 F = dp/dt，但在质量不变时简化为 F = ma。注意必须使用合力，而不是某一个施加力。
2. Materials: Stress, Strain and the Young Modulus | 材料：应力、应变与杨氏模量
Stress is defined as force per unit cross-sectional area, and strain is extension per original length. Both are needed to calculate the Young modulus.
应力定义为单位横截面积上的力，应变定义为原始长度上的伸长量。两者用于计算杨氏模量。
σ = F/A, ε = ΔL/L, E = σ/ε
Stress-strain graphs show the elastic limit, yield point and plastic deformation. The area under a force-extension graph gives the work done or stored elastic strain energy.
应力-应变图可展示弹性极限、屈服点和塑性形变。力-伸长图下的面积等于做功或储存的弹性应变能。
Edexcel questions often ask you to compare the properties of brittle and ductile materials, so describe the shape of the graph and the meaning of its gradient.
Edexcel 考题常要求比较脆性材料和延性材料的性质，因此要描述图线的形状及其斜率的含义。
3. Electric Circuits: Ohm's Law and Potential Dividers | 电路：欧姆定律与分压器
Ohm's law applies to ohmic conductors at constant temperature. In an I-V graph, a fixed resistor gives a straight line through the origin, while a filament lamp curves because resistance increases with temperature.
欧姆定律适用于温度恒定的欧姆导体。在 I-V 图中，固定电阻是一条过原点的直线，而灯丝曲线弯曲是因为电阻随温度升高而增大。
V = IR, P = IV = I²R = V²/R
A potential divider uses two resistors in series to produce a desired output voltage. This is a favourite Edexcel combined question with sensors such as LDRs and thermistors.
分压器利用两个串联电阻产生所需输出电压。这是 Edexcel 综合题常考内容，常与光敏电阻和热敏电阻等传感器结合。
Vout = Vin × R₂/(R₁ + R₂)
When using this equation, identify which resistor you are measuring across, because the output voltage depends on the ratio of its resistance to the total resistance.
使用该公式时，要明确测量的是哪个电阻两端的电压，因为输出电压取决于该电阻阻值与总阻值之比。
4. Waves: Superposition and Interference | 波动：叠加与干涉
Coherent waves have the same frequency and a constant phase difference. Constructive interference occurs when the path difference is nλ, and destructive interference occurs when it is (n + ½)λ.
相干波具有相同频率和恒定相位差。当波程差为 nλ 时发生相长干涉，当波程差为 (n + ½)λ 时发生相消干涉。
Δx = λD/d, d sin θ = nλPublished by TutorHao | A-Level Revision Series | aleveler.com
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