📚 Cambridge IGCSE Physics Complete Revision Guide | 剑桥 IGCSE 物理完整复习指南
Cambridge IGCSE Physics (0625) is one of the most popular international qualifications for students aged 14-16. The syllabus covers a wide range of topics, from mechanics and thermal physics to waves, electricity, atomic physics and space physics. This revision guide summarises the key ideas, equations and exam skills you need to succeed.
剑桥 IGCSE 物理（0625）是 14-16 岁学生最受欢迎的国际资格证书之一。课程大纲涵盖力学、热物理学、波、电学、原子物理和空间物理等广泛主题。本复习指南总结了你取得成功所需的核心概念、公式和应试技巧。
1. Exam Overview | 考试概览
The CIE IGCSE Physics syllabus (0625) is available at Core and Extended levels. Core candidates take Papers 1 and 3, while Extended candidates take Papers 2 and 4. All candidates also sit either Paper 5 (Practical Test) or Paper 6 (Alternative to Practical).
CIE IGCSE 物理大纲（0625）提供核心（Core）和拓展（Extended）两个级别。核心考生参加试卷 1 和 3，拓展考生参加试卷 2 和 4。所有考生还需参加试卷 5（实验操作）或试卷 6（实验替代笔试）。
Paper 1 and Paper 2 contain 40 multiple-choice questions each. Paper 3 and Paper 4 are written theory papers with short-answer and longer structured questions. Extended papers include more challenging applications, such as momentum calculations and electromagnetic induction.
试卷 1 和试卷 2 各包含 40 道选择题。试卷 3 和试卷 4 是书面理论卷，包含简答题和较长的结构化问题。拓展试卷包含更具挑战性的应用，例如动量计算和电磁感应。
The final grade is based on a weighted combination of the theory paper and the practical paper. Understanding the structure helps you allocate revision time effectively.
最终成绩基于理论卷和实验卷的加权组合。了解试卷结构有助于你合理分配复习时间。
2. Motion, Forces and Energy | 运动、力与能量
Speed is the distance travelled per unit time, while velocity is speed in a given direction. Acceleration is the rate of change of velocity. The equations of motion link initial velocity u, final velocity v, acceleration a, time t and displacement s.
速率是单位时间内移动的距离，而速度是给定方向上的速率。加速度是速度的变化率。运动学方程将初速度 u、末速度 v、加速度 a、时间 t 和位移 s 联系起来。
v = u + at
s = ut + ½at²
Newton' n object remains at rest or in uniform motion unless acted on by a resultant force. Newton' by F = ma, and the third law states that every action has an equal and opposite reaction.
牛顿第一定律指出，除非受到合外力作用，物体将保持静止或匀速直线运动。牛顿第二定律可概括为 F = ma，第三定律指出每一个作用力都有一个大小相等、方向相反的反作用力。
ergy, chemical energy and internal energy. Work done and power are key quantities in energy transfers.
能量可以储存为动能 Eₖ = ½mv²、重力势能 Eₚ = mgh、弹性势能、化学能和内能。功和功率是能量转移中的关键物理量。
3. Thermal Physics | 热物理学
Matter exists in solid, liquid and gas states. The kinetic particle model explains properties such as density, expansion and pressure in terms of particle motion and spacing. Brownian motion provides evidence for random molecular movement.
物质以固态、液态和气态存在。动力学粒子模型用粒子的运动和间距解释密度、膨胀和压强等性质。布朗运动为分子的无规则运动提供了证据。
. Specific heat capacity c relates energy change to mass and temperature change: Q = mcΔT.
温度测量粒子的平均动能，而热量是内能的转移。比热容 c 将能量变化与质量和温度变化联系起来：Q = mcΔT。
. For a fixed mass of gas at constant temperature, pressure and volume obey pV = constant.
潜热是物质在恒定温度下发生状态变化时吸收或释放的能量。比潜热 L 用于方程 Q = mL。对于一定质量的气体，在恒温条件下，压强和体积遵循 pV = 常量。
4. Waves | 波
Waves transfer energy without transferring matter. Transverse waves have oscillations perpendicular to the direction of energy transfer, while longitudinal waves have oscillations parallel to it. Sound waves are longitudinal; light and water waves are transverse.
波传递能量而不传递物质。横波的振动方向垂直于能量传递方向，纵波的振动方向平行于能量传递方向。声波是纵波；光波和水波是横波。
ction, refraction and diffraction are key wave behaviours. Total internal reflection occurs when light travels from a denser to a less dense medium at an angle greater than the critical angle.
波动方程将速度 v、频率 f 和波长 λ 联系起来：v = fλ。反射、折射和衍射是波的关键行为。当光从光密介质射向光疏介质且入射角大于临界角时，会发生全反射。
gamma rays. All electromagnetic waves travel at the same speed in a vacuum: 3.0 × 10⁸ m/s.
电磁波谱包括无线电波、微波、红外线、可见光、紫外线、X 射线和伽马射线。所有电磁波在真空中的速度相同：3.0 × 10⁸ m/s。
5. Electricity and Magnetism | 电与磁
ence (voltage) is the energy transferred per unit charge. Resistance is defined by V = IR.
电流是电荷流动的速率。电荷 Q、电流 I 和时间 t 的关系为 Q = It。电势差（电压）是每单位电荷转移的能量。电阻由 V = IR 定义。
voltage is the same across branches and total resistance is found from 1/R = 1/R₁ + 1/R₂.
在串联电路中，各处电流相同，总电阻为 R = R₁ + R₂。在并联电路中，各支路电压相同，总电阻由 1/R = 1/R₁ + 1/R₂ 求得。
rs, generators and transformers. A transformer changes voltage according to Vₚ/Vₛ = Nₚ/Nₛ.
电功率可用 P = IV、P = I²R 或 P = V²/R 计算。磁学和电磁学是电动机、发电机和变压器的基础。变压器根据 Vₚ/Vₛ = Nₚ/Nₛ 改变电压。
6. Atomic Physics | 原子物理
An atom consists of a small, dense nucleus containing protons and neutrons, surrounded by electrons in shells. The proton number Z defines the element, and the nucleon number A is the total number of protons and neutrons.
原子由一个包含质子和中子的致密小原子核以及核外分层排布的电子组成。质子数 Z 决定了元素种类，核子数 A 是质子数与中子数之和。
Isotopes are atoms of the same element with different numbers of neutrons. Some isotopes are unstable and emit ionising radiation: alpha particles (helium nuclei), beta particles (fast electrons) and gamma rays (electromagnetic waves).
同位素是同一元素中中子数不同的原子。一些同位素不稳定，会发射电离辐射：α 粒子（氦核）、β 粒子（高速电子）和 γ 射线（电磁波）。
Radioactive decay is random and can be described by half-life, the time taken for half the nuclei in a sample to decay. Nuclear equations must balance both proton number and nucleon number. Nuclear fission and fusion release large amounts of energy.
放射性衰变是随机的，可以用半衰期来描述，即样品中半数原子核发生衰变所需的时间。核反应方程必须同时满足质子数和核子数守恒。核裂变和核聚变释放大量能量。
7. Space Physics | 空间物理
The Earth rotates on its axis once every 24 hours and orbits the Sun once a year. The Solar System consists of the Sun, eight planets, dwarf planets, moons, asteroids and comets. Gravitational force keeps planets in orbit.
地球每 24 小时绕地轴自转一周，每年绕太阳公转一周。太阳系由太阳、八大行星、矮行星、卫星、小行星和彗星组成。引力使行星保持在轨道上运行。
Stars form from clouds of gas and dust, undergo nuclear fusion of hydrogen into helium, and eventually evolve into red giants, white dwarfs, neutron stars or black holes depending on their mass. The Sun is a main-sequence star.
恒星由气体和尘埃云形成，通过氢聚变为氦的核聚变反应产生能量，并根据质量最终演化为红巨星、白矮星、中子星或黑洞。太阳是一颗主序星。
Redshift of light from distant galaxies shows that the Universe is expanding. This supports the Big Bang theory. Hubble's law states that the speed of recession of a galaxy is proportional to its distance from us.
来自遥远星系的光发生红移表明宇宙正在膨胀。这支持了大爆炸理论。哈勃定律指出，星系远离我们的速度与其距离成正比。
8. Practical Skills | 实验技能
Paper 5 and Paper 6 test your ability to plan experiments, record data, draw graphs and evaluate sources of error. Common experiments include measuring the density of regular and irregular objects, investigating resistance, and determining the focal length of a lens.
试卷 5 和试卷 6 考查你设计实验、记录数据、绘制图表和评估误差来源的能力。常见实验包括测量规则和不规则物体的密度、研究电阻以及测定透镜焦距。
Always record units, use an appropriate number of significant figures and plot graphs with labelled axes. For a straight-line graph, the gradient and intercept often give useful quantities, such as resistance or acceleration.
始终记录单位，使用恰当的数值位数，并绘制带有坐标轴标签的图表。对于直线图，斜率和截距通常能给出有用的物理量，例如电阻或加速度。
When evaluating an experiment, identify systematic errors (which affect accuracy) and random errors (which affect precision). Suggest realistic improvements, such as repeating readings or using a more sensitive instrument.
评估实验时，要区分系统误差（影响准确度）和随机误差（影响精密度）。提出切实可行的改进措施，例如重复读数或使用更灵敏的仪器。
9. Common Mistakes | 常见错误
weight is a force measured in newtons and depends on gravitational field strength: W = mg.
一个常见错误是混淆质量和重量。质量以千克为单位，是标量；而重量是一种力，以牛顿为单位，取决于重力场强度：W = mg。
y transferred per second, so 1 W = 1 J/s. Convert minutes to seconds before using P = E/t.
另一个常见错误是能量、功率和时间的单位使用不当。记住功率是每秒转移的能量，因此 1 W = 1 J/s。在使用 P = E/t 之前，要先将分钟转换为秒。
When drawing ray diagrams, many students forget to draw arrows on rays or label the normal. In circuit questions, failure to distinguish series and parallel connections often leads to incorrect resistance calculations.
在绘制光线图时，许多学生忘记在光线上标箭头或标记法线。在电路题中，未能区分串联和并联往往导致电阻计算错误。
10. Exam Tips | 备考策略
Read command words carefully. 'State' requires a brief answer, 'describe' requires a step-by-step account, and 'explain' requires a scientific reason. Show all your working in calculations, as method marks can be awarded even if the final answer is wrong.
仔细阅读指令词。“State”要求简要回答，“describe”要求分步描述，“explain”要求给出科学原因。在计算题中写出所有解题步骤，因为即使最终答案错误，也可能获得步骤分。
Manage your time by allocating marks per minute. For example, a 3-mark question deserves about 3 minutes. Leave time at the end to check units, significant figures and circuit symbols.
合理分配时间，按分数分配分钟。例如，一道 3 分的题大约用 3 分钟。最后留出时间检查单位、有效数字和电路符号。
Practise past papers under timed conditions and use the mark scheme to understand what examiners expect. Focus on the topics that appear most frequently, such as motion, electricity and waves.
在限时条件下练习历年真题，并利用评分标准了解阅卷人的要求。重点复习出现频率最高的主题，例如运动、电学和波。
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