📚 Cambridge IGCSE Physics Core Knowledge Review | 剑桥IGCSE物理核心知识点梳理
This article consolidates the essential topics covered in the Cambridge IGCSE Physics syllabus (0625/0972) for Year 11 students. A thorough understanding of these core principles - from mechanics and thermal physics to waves, electricity and modern physics - is vital for examination success and for building a strong foundation for future scientific study. Each section below pairs the key definitions, equations and graph skills that examiners repeatedly test with the explanations that candidates most often get wrong.
本文梳理了剑桥 IGCSE 物理大纲（0625/0972）中 Year 11 学生需要掌握的核心知识点。深入理解力学、热物理、波、电学乃至现代物理这些基本原理，不仅是考试成功的关键，也为今后的科学学习打下坚实基础。下文每一节都把考官反复考查的核心定义、公式与图像技能，与考生最容易出错的解释性内容配对呈现，方便逐条核对复习。
1. General Physics: Motion and Measurements | 普通物理：运动与测量
Physics begins with measurement. Every quantity in the IGCSE course is expressed in SI units: length in metres (m), mass in kilograms (kg), time in seconds (s), current in amperes (A), temperature in kelvin (K), amount of substance in moles (mol) and luminous intensity in candela (cd). Prefixes allow very large or very small values to be written compactly, and you are expected to convert fluently between them.
物理从测量开始。IGCSE 课程中的每一个量都用国际单位制（SI）表示：长度用米（m）、质量用千克（kg）、时间用秒（s）、电流用安培（A）、温度用开尔文（K）、物质的量用摩尔（mol）、发光强度用坎德拉（cd）。词头让极大或极小的数值可以写得简洁，你需要能在它们之间熟练换算。
| Prefix | Symbol | Factor |
| giga | G | 10⁹ |
| mega | M | 10⁶ |
| kilo | k | 10³ |
| milli | m | 10⁻³ |
| micro | µ | 10⁻⁶ |
| nano | n | 10⁻⁹ |
Quantities are then classified as scalars (magnitude only) or vectors (magnitude and direction). Distance, speed, mass, time, energy and temperature are scalars; displacement, velocity, acceleration, force, weight and momentum are vectors. Confusing distance with displacement is one of the most common sources of lost marks.
接下来，物理量被分为标量（只有大小）和矢量（既有大小又有方向）。距离、速率、质量、时间、能量和温度是标量；位移、速度、加速度、力、重力和动量是矢量。把距离与位移混为一谈，是最常见的失分原因之一。
Speed is the rate of change of distance, while velocity is the rate of change of displacement. Acceleration is the rate of change of velocity, and a negative acceleration indicates deceleration. On a distance-time graph the gradient gives speed; on a velocity-time graph the gradient gives acceleration and the area under the line gives the distance travelled.
速率是距离的变化率，而速度是位移的变化率。加速度是速度的变化率，负的加速度表示减速。在距离-时间图上，斜率表示速率；在速度-时间图上，斜率表示加速度，图线下方围出的面积表示走过的距离。
v = Δd / Δt a = Δv / Δt v² = u² + 2as
In free fall near the Earth's surface all objects accelerate downwards at about 9.8 m/s² (commonly approximated as 10 m/s²), irrespective of their mass, provided air resistance is negligible.
在地球表面附近的自由落体中，只要空气阻力可以忽略，所有物体都以约 9.8 m/s²（通常近似取 10 m/s²）向下加速，与它们的质量无关。
2. Forces, Density and Pressure | 力、密度与压强
A force is a vector quantity measured in newtons (N). It can change an object's speed, direction or shape. Newton's first law states that an object remains at rest or moves at constant velocity unless acted on by a resultant force; Newton's second law relates the resultant force to mass and acceleration.
力是用牛顿（N）测量的矢量。它可以改变物体的速率、方向或形状。牛顿第一定律指出：除非受到合力作用，物体保持静止或做匀速运动；牛顿第二定律则把合力与质量和加速度联系起来。
Weight is the gravitational force on a mass and must never be confused with mass itself. Weight changes with the gravitational field strength g, whereas mass is constant everywhere in the universe.
重力是作用在质量上的引力，绝不能与质量本身混淆。重力会随重力场强度 g 变化，而质量在宇宙任何地方都不变。
mg ρ = m / V p = F / A p = ρgh F = kx
Density is mass per unit volume and explains floating and sinking. Pressure is force per unit area, and in a liquid pressure increases with depth and with density. Hooke's law tells us that the extension of a spring is directly proportional to the load applied, up to the limit of proportionality, after which the graph curves and the spring is permanently deformed.
密度是单位体积的质量，它解释了物体的浮与沉。压强是单位面积上所受的力，在液体中压强随深度和密度的增加而增大。胡克定律告诉我们：在弹性限度内，弹簧的伸长量与所加载荷成正比；超过这个限度后图线弯曲，弹簧发生永久形变。
Turning effect: moment = force × perpendicular distance from the pivot, measured in N m.
转动效应：力矩 = 力 × 到支点的垂直距离，单位为 N m。
Equilibrium: the total clockwise moment equals the total anticlockwise moment, and the resultant force is zero.
平衡条件：顺时针力矩总和等于逆时针力矩总和，且合力为零。
Upthrust: an object floats when the upthrust equals its weight, and sinks when the upthrust is smaller.
浮力：浮力等于重力时物体漂浮，浮力小于重力时物体下沉。
Terminal velocity: drag increases with speed until it balances weight, so acceleration becomes zero.
终端速度：阻力随速率增大，直到与重力平衡，加速度变为零。
3. Energy, Work and Power | 能量、功与功率
Energy is the capacity to do work and is measured in joules (J). It cannot be created or destroyed, only transferred between stores: kinetic, gravitational potential, elastic potential, chemical, thermal, nuclear, and energy carried by waves or electricity. A sankey diagram is the standard way of showing these transfers and the wasted energy.
能量是做功的本领，用焦耳（J）测量。能量既不能创生也不能消灭，只能在各种能量形式之间转移：动能、重力势能、弹性势能、化学能、内能、核能，以及由波或电流携带的能量。桑基图是展示这些能量转移与损耗能量的标准方式。
W = Fd P = W / t = E / t Ek = ½mv² Ep = mgh
Work is done when a force moves an object through a distance in the direction of the force. Power is the rate of doing work, or the rate of energy transfer, and is measured in watts (W). One watt equals one joule per second.
当力使物体沿力的方向移动一段距离时，就说这个力做了功。功率是做功的速率，也就是能量转移的速率，用瓦特（W）测量。1 瓦特等于每秒 1 焦耳。
Efficiency compares useful output energy with total input energy. Efficiency can never exceed 100 per cent because some energy is always dissipated to the surroundings, usually as thermal energy.
效率比较的是有用的输出能量与总输入能量。效率永远不可能超过 100%，因为总有一部分能量耗散到周围环境中，通常以内能的形式散失。
efficiency = useful energy output / total energy input × 100%
Renewable resources such as solar, wind, hydroelectric, geothermal, tidal and biomass replenish themselves, while fossil fuels and nuclear fuel are non-renewable. Each has advantages and disadvantages in terms of reliability, cost, pollution and suitability for a given location.
太阳能、风能、水能、地热能、潮汐能和生物质能等可再生资源可以自我补充，而化石燃料和核燃料属于不可再生资源。在可靠性、成本、污染以及是否适合某一地区等方面，它们各有优缺点。
4. Thermal Physics: Kinetic Model and Heat Transfer | 热物理：分子模型与传热
The kinetic particle model explains the properties of solids, liquids and gases in terms of the arrangement, spacing and motion of particles. Temperature is a measure of the average kinetic energy of the particles, while internal energy is the total kinetic and potential energy of all the particles in a body.
分子动理论用粒子的排列、间距和运动来解释固体、液体和气体的性质。温度是粒子平均动能的量度，而内能是物体内所有粒子的动能与势能的总和。
Brownian motion - the random zig-zag movement of smoke or pollen particles suspended in a fluid - provides direct evidence for the random motion of molecules. As a substance is heated, its particles gain kinetic energy and move faster, so the substance expands.
布朗运动——悬浮在流体中的烟雾或花粉颗粒所做的无规则折线运动——为分子的无规则运动提供了直接证据。物质被加热时，粒子获得动能、运动加快，因此物质膨胀。
Q = mcΔT E = mL p₁V₁ = p₂V₂
Specific heat capacity is the energy needed to raise the temperature of 1 kg of a substance by 1 °C. Specific latent heat is the energy needed to change the state of 1 kg of a substance without any change in temperature. During melting or boiling, energy is used to break the bonds between particles rather than to raise the temperature.
比热容是使 1 kg 某物质温度升高 1 °C 所需的能量。比潜热是使 1 kg 某物质发生物态变化而不改变温度所需的能量。在熔化或沸腾过程中，能量用于破坏粒子间的结合，而不是用来升高温度。
Conduction: transfer by particle vibration and free electron diffusion, best in metals.
传导：通过粒子振动和自由电子扩散传递能量，在金属中最有效。
Convection: transfer by the bulk movement of a heated fluid, which becomes less dense and rises.
对流：通过受热流体的整体流动传递能量，受热流体密度变小而上升。
Radiation: transfer by infrared waves, requires no medium, and is reduced by shiny, light-coloured surfaces.
辐射：通过红外波传递，不需要介质，表面光亮、颜色浅可减少辐射。
Evaporation: the escape of the fastest particles from a liquid surface, which cools the remaining liquid.
蒸发：液体表面最快的粒子逃逸出去，使剩余液体温度下降。
mbined relationship pV / T = constant can be applied, with temperature measured in kelvin.
对于一定质量的气体，在温度不变时，压强与体积成反比。如果温度也在变化，可用组合关系 pV / T = 常数，此时温度必须用开尔文表示。
5. Waves and Sound | 波与声
A wave is a transfer of energy without the transfer of matter. In a transverse wave the oscillations are perpendicular to the direction of travel, for example light and water ripples; in a longitudinal wave they are parallel, for example sound. Amplitude, wavelength, frequency and period are the quantities used to describe any wave.
波是在不传递物质的情况下传递能量。横波中振动方向与传播方向垂直，例如光和水的波纹；纵波中振动方向与传播方向平行，例如声波。振幅、波长、频率和周期是描述任何波的四个基本物理量。
v = fλ T = 1 / f
All waves can be reflected, refracted, diffracted and, when coherent, made to interfere. Diffraction is most noticeable when the wavelength is similar to the size of the gap or obstacle. Refraction occurs because the speed of
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