📚 GCSE CIE Physics: Last-Minute Revision Notes | GCSE CIE 物理：考前冲刺笔记
Preparing for your CIE GCSE Physics exam? This last-minute revision guide distils the essential concepts, equations, and practical advice to boost your confidence. Use these notes to quickly review key topics and sharpen your exam technique.
正在准备 CIE GCSE 物理考试？这份考前冲刺笔记浓缩了核心概念、公式和实用建议，助你提升信心。用此笔记快速回顾重点主题，打磨考试技巧。
1. Motion & Kinematics | 运动与运动学
ector; it includes direction. The gradient of a distance-time graph gives speed. A horizontal line on a distance-time graph means the object is stationary; a curved line means acceleration.
速率是标量，只有大小。平均速率 = 总路程 ÷ 时间 (v = s / t)。速度是矢量，包含方向。距离-时间图的斜率给出速率。距离-时间图的水平线段表示物体静止；曲线表示有加速度。
The gradient of a velocity-time graph gives acceleration. The area under a velocity-time graph gives the distance travelled. For uniform acceleration, three key equations apply (often called SUVAT).
速度-时间图的斜率给出加速度。速度-时间图下的面积给出移动的距离。对于匀加速直线运动，三个关键方程适用 (常称为 SUVAT)。
| Equation | Useful when you do not know |
|---|---|
| v = u + at | s |
| v² = u² + 2as | t |
| s = ut + ½at² | v (but you need t) |
ty, a = acceleration, t = time, s = displacement. Acceleration due to free fall near Earth's surface is g ≈ 9.8 m/s²; in exams you may be told to use 10 m/s².
其中 u = 初速度, v = 末速度, a = 加速度, t = 时间, s = 位移。地表附近的自由落体加速度 g ≈ 9.8 m/s²；考试中可能要求取 10 m/s²。
2. Forces & Newton’s Laws | 力与牛顿定律
orce. Newton’s Second Law: F = ma, where F is resultant force, m is mass, a is acceleration. Newton’s Third Law: action and reaction forces are equal in magnitude and opposite in direction, but act on different bodies.
力是推或拉，以牛顿 (N) 为单位。牛顿第一定律：物体保持静止或匀速直线运动状态，除非受到合外力作用。牛顿第二定律：F = ma，其中 F 是合外力，m 是质量，a 是加速度。牛顿第三定律：作用力与反作用力大小相等、方向相反，但作用在不同物体上。
Friction opposes motion and can be useful (walking, braking) or a nuisance (waste of energy). Terminal velocity occurs when the resistive force (air resistance) balances the weight, so the resultant force becomes zero and the object falls at constant speed.
摩擦力阻碍运动，可能有益 (行走、刹车) 也可能有害 (浪费能量)。当阻力 (空气阻力) 与重力平衡时，合外力为零，物体达到终末速度，匀速下落。
ce from the pivot. For an object in equilibrium, the sum of clockwise moments equals the sum of anticlockwise moments, and there is no resultant force.
力矩：力对支点的力矩 = 力 × 力臂 (支点到力作用线的垂直距离)。物体处于平衡态时，顺时针力矩之和等于逆时针力矩之和，且合外力为零。
3. Energy, Work & Power | 能量、功与功率
netic energy (KE) = ½mv². Gravitational potential energy (GPE) = mgh, where h is the vertical height.
当力使物体沿力的方向移动时，力做了功：W = F × d。能量是做功的本领；两者的 SI 单位都是焦耳 (J)。动能 (KE) = ½mv²。重力势能 (GPE) = mgh，其中 h 为垂直高度。
ot be created or destroyed. Efficiency = (useful energy output / total energy input) × 100%. In Sankey diagrams, the width of arrows represents the amount of energy.
能量守恒：能量可在不同形式 (动能、内能、化学能等) 之间传递，但不会凭空产生或消失。效率 = (有用能量输出 / 总能量输入) × 100%。在桑基图中，箭头的宽度表示能量的大小。
/s. P = E / t, and also P = Fv for an object moving at constant speed v against a force F.
功率 = 做功 / 所用时间，或能量传递 / 时间。单位是瓦特 (W)，1 W = 1 J/s。P = E / t，对于克服恒力以恒速 v 运动的物体，有 P = Fv。
4. Momentum | 动量
. It is a vector quantity. In a closed system, total momentum before a collision equals total momentum after (principle of conservation of momentum).
动量 (p) = 质量 × 速度 (p = mv)。它是矢量。在封闭系统内，碰撞前的总动量等于碰撞后的总动量 (动量守恒定律)。
rbags, crumple zones, and seat belts increase the time over which a collision occurs, reducing the force on the passengers.
冲量 = 力 × 时间 = 动量的变化。Ft = Δp。安全气囊、溃缩区和安全带等延长了碰撞的作用时间，从而减小乘客所受的力。
For elastic collisions, both momentum and kinetic energy are conserved. For inelastic collisions, momentum is conserved but kinetic energy is not (some is converted to heat or sound).
在弹性碰撞中，动量和动能均守恒。在非弹性碰撞中，动量守恒，但动能不守恒 (部分转化为热或声)。
5. Thermal Physics | 热物理
te zero (0 K = −273 °C) is the temperature at which particles have minimum kinetic energy.
温度衡量的是粒子的平均动能；温度不同于热量。常用单位：摄氏度 (°C) 和开尔文 (K)。绝对零度 (0 K = −273 °C) 是粒子动能最小时的温度。
Thermal expansion: most solids, liquids, and gases expand when heated because particles vibrate more and move farther apart. The bimetallic strip bends when heated due to different expansion rates of the two metals.
热膨胀：多数固体、液体和气体受热时因粒子振动加剧、间距增大而膨胀。双金属片受热时因两种金属膨胀率不同而弯曲。
eeded to change the state of 1 kg of a substance without changing its temperature: Q = mL. Latent heat of fusion: solid ⇌ liquid; latent heat of vaporisation: liquid ⇌ gas.
比热容 (c) 是使 1 kg 物质升高 1 °C 所需的能量：Q = mcΔθ。比潜热 (L) 是使 1 kg 物质在温度不变的情况下改变状态所需的能量：Q = mL。熔解潜热：固态 ⇌ 液态；汽化潜热：液态 ⇌ 气态。
6. Waves | 波
Waves transfer energy without transferring matter. Transverse waves: oscillations are perpendicular to the direction of energy travel (e.g. light, water waves). Longitudinal waves: oscillations are parallel to the direction of energy travel (e.g. sound).
波传递能量而不传递物质。横波：振动方向垂直于能量传播方向 (如光波、水波)。纵波：振动方向平行于能量传播方向 (如声波)。
metres. The period T = 1/f. Amplitude is the maximum displacement from the rest position.
波速 v = f λ，f 为频率 (Hz)，λ 为波长 (m)。周期 T = 1/f。振幅是离开平衡位置的最大位移。
le of reflection, measured to the normal. Refraction: waves change speed and direction when entering a different medium. For light going into a denser medium, it bends towards the normal and slows down.
反射：入射角 = 反射角，均从法线量起。折射：波进入不同介质时速度和方向发生改变。光进入光密介质时，向法线偏折且速度减慢。
violet, X-ray, gamma. All EM waves travel at the same speed in a vacuum (c = 3 × 10⁸ m/s).
电磁波谱 (按频率和能量递增排列)：无线电波、微波、红外线、可见光、紫外线、X 射线、伽马射线。所有电磁波在真空中传播速度相同 (c = 3 × 10⁸ m/s)。
7. Electricity | 电学
In a series circuit, current is the same everywhere. In a parallel circuit, the total current is the sum of the branch currents.
电流 (I) 是电荷流动的速率：I = Q / t。单位是安培 (A)。串联电路中电流处处相等。并联电路中总电流等于各支路电流之和。
istors, voltage splits in proportion to resistance. In parallel branches, voltage is the same across each branch.
电压 (电势差, V) 衡量单位电荷转移的能量：V = W / Q。串联电阻两端电压按电阻比例分配。并联支路两端电压均相等。
sectional area, and material: R = ρL / A. For filament lamps, resistance increases with temperature; for diodes, current flows in one direction only.
欧姆定律：对温度恒定的电阻器，V = IR。电阻 R 以欧姆 (Ω) 为单位。导线的电阻取决于长度、横截面积和材料：R = ρL / A。灯丝的电阻随温度升高而增大；二极管只允许单向电流通过。
ic circuits, the live, neutral, and earth wires are used; fuses and circuit breakers protect against overcurrent.
电功率：P = IV = I²R = V² / R。电能：E = IVt。家庭电路中设有火线、零线和地线；熔断器和断路器用于过流保护。
8. Magnetism & Electromagnetism | 磁与电磁学
Magnets have north and south poles; like poles repel, unlike poles attract. A magnetic field line shows the direction of the force on a north pole. The field is strongest where lines are closest together.
磁铁有 N 极和 S 极；同名极相斥，异名极相吸。磁感线方向表示 N 极受力方向。磁感线越密，磁场越强。
An electromagnet is created by passing a current through a coil (solenoid) often containing an iron core. Its strength can be increased by increasing the current, adding more turns, or using a soft iron core.
电磁铁由电流通过线圈 (螺线管) 产生，通常包含铁芯。增大电流、增加线圈匝数或使用软铁芯均可增强其磁性。
e F = BIL, where B is magnetic flux density. This is used in loudspeakers and d.c. motors.
电动机效应：磁场中的载流导线会受到力的作用 (弗莱明左手定则)。对长度为 L 的导线，F = BIL，B 为磁通量密度。该效应用于扬声器和直流电动机。
Electromagnetic induction: when a conductor cuts magnetic field lines (or the field changes), a voltage is induced. This is the principle behind generators and dynamos. The size of induced voltage can be increased by moving the wire faster, using a stronger magnet, or increasing the number of coil turns.
电磁感应：当导体切割磁感线 (或磁场变化) 时，会感应出电压。这是发电机和发电机的原理。增大切割速度、使用更强磁铁或增加线圈匝数均可增大感应电压。
e current; step-down transformers do the opposite. Power is almost conserved: VₚIₚ ≈ VₛIₛ.
变压器改变交流电压：Vₚ / Vₛ = Nₚ / Nₛ (理想情况)。升压变压器升高电压、减小电流；降压变压器相反。功率近似守恒：VₚIₚ ≈ VₛIₛ。
9. Atomic Physics & Radioactivity | 原子物理与放射性
of protons; mass number A = protons + neutrons. Isotopes have the same Z but different A.
原子由原子核 (质子 + 中子) 和核外分层排布的电子组成。原子序数 Z = 质子数；质量数 A = 质子数 + 中子数。同位素具有相同的 Z 但不同的 A。
Radioactive decay is a random process where unstable nuclei emit radiation. Alpha particles (α): helium nucleus ⁴₂He, highly ionising, stopped by paper. Beta particles (β): fast electron, moderately ionising, stopped by aluminium. Gamma rays (γ): electromagnetic wave, weakly ionising, stopped by thick lead or concrete.
放射性衰变是随机的：不稳定的原子核释放辐射。α 粒子：氦核 ⁴₂He，电离能力强，可被纸张阻挡。β 粒子：高速电子，电离能力中等，可被铝片阻挡。γ 射线：电磁波，电离能力弱，需厚铅板或混凝土阻挡。
Background radiation comes from rocks, cosmic rays, and medical sources. Half-life is the time taken for half the radioactive nuclei in a sample to decay. The activity (Bq) halves each half-life. Half-life data can be used to date materials or plan medical treatments.
本底辐射来源于岩石、宇宙射线和医疗等。半衰期是样品中一半放射性原子核发生衰变所需的时间。放射性活度 (Bq) 每经过一个半衰期减半。半衰期可用于材料年代测定或医疗计划。
Nuclear equations: the sum of top numbers (mass) and bottom numbers (atomic number) must balance. In beta decay, a neutron changes to a proton, emitting an electron and an antineutrino.
核方程：左上角 (质量数) 和左下角 (原子序数) 的总和必须平衡。β 衰变中，一个中子转变为一个质子，并释放一个电子和一个反中微子。
10. Space Physics | 空间物理
The Earth rotates on its axis once every 24 hours, causing day and night. It orbits the Sun once every 365.25 days. The Moon orbits the Earth about every 28 days. The gravitational force keeps these bodies in orbit.
地球每 24 小时自转一周，产生昼夜更替。地球绕太阳公转周期约 365.25 天。月球绕地球公转约 28 天。万有引力使这些天体保持在轨道上。
Our Solar System is in the Milky Way galaxy. A star’s life cycle depends on its mass: stars like the Sun end as planetary nebulae and white dwarfs; much more massive stars can become red supergiants and then explode as supernovae, leaving behind neutron stars or black holes.
我们的太阳系位于银河系内。恒星的演化取决于质量：类太阳恒星最终形成行星状星云和白矮星；质量大得多的恒星可变为红超巨星，继而超新星爆发，留下中子星或黑洞。
Redshift of light from distant galaxies shows they are moving away, providing evidence for the expanding Universe and the Big Bang theory. The Cosmic Microwave Background Radiation (CMBR) is another key piece of evidence.
遥远星系光谱的红移表明它们正在远离，为宇宙膨胀和大爆炸理论提供了证据。宇宙微波背景辐射 (CMBR) 也是重要证据。
11. Practical Skills & Key Experiments | 实验技能与重点实验
Learn to identify independent, dependent, and control variables. For graphs, draw axes labelled with quantities and units, plot points accurately, and draw a line of best fit. The gradient and intercept often represent physical quantities.
学会识别自变量、因变量和控制变量。绘图时，坐标轴要标明物理量和单位，点要准确描出，并画出最佳拟合线。斜率和截距常代表相应的物理量。
determining the specific heat capacity of a metal block using an electric heater; measuring the IV characteristics of a resistor, lamp, and diode; determining the focal length of a lens; investigating waves in a ripple tank; and measuring the half-life of a radioactive source using a Geiger-Müller counter.
核心实验：用光门测速度；用弹簧探究胡克定律 (F = kx)；用电加热器测定金属块的比热容；测量电阻、灯和二极管的 IV 特性；测定透镜焦距；用波动槽探究波的性质；以及使用盖革-米勒计数器测量放射源的半衰期。
Always take repeat readings and calculate the mean to minimise random errors. A zero error in a measuring instrument (e.g. ammeter not reading zero when no current flows) causes a systematic error, which can be corrected by subtracting or adding the offset.
始终进行重复测量并计算平均值，以减少随机误差。测量仪器的零误差 (如电流表在无电流时未指零) 会引起系统误差，可通过减去或加上偏置值来修正。
12. Exam Tips & Common Mistakes | 考试技巧与常见错误
Read the question carefully: underline command words such as 'describe', 'explain', 'calculate', and 'compare'. 'Explain' requires using scientific principles (e.g. particles, forces, energy) to give reasons.
仔细读题：圈画出指令词如 “describe”(描述)、“explain”(解释)、“calculate”(计算)、“compare”(比较)。解释类问题需引用科学原理 (如粒子、力、能量) 来说明原因。
Manage your time: don’t spend too long on one calculation. If a question asks for the unit, always include it. For multi-step calculations, show all working to gain method marks even if the final answer is wrong.
合理分配时间：不要在单个计算题上耗时过多。若题目要求给出单位，务必写上。对多步计算题，展示完整的解题过程，即使最终答案有误也能获得步骤分。
In graph questions, use a sharp pencil, scale the axes sensibly, and check if the origin (0,0) is necessary. To find the gradient, draw a large triangle on the line and use coordinates, not data points.
做图题时，用铅笔、合理设定坐标轴刻度，并检查是否需要原点 (0,0)。求斜率时
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