📚 Year 9 WJEC Physics: Core Knowledge Review | WJEC 九年级物理：核心知识点梳理
This article provides a comprehensive summary of the key topics covered in the Year 9 WJEC Physics curriculum. It is designed to help you revise the essential concepts, from energy and forces to waves and electricity, with clear explanations that mirror the structure of your lessons. Use this guide to consolidate your understanding and prepare confidently for assessments.
本文全面总结了 WJEC 九年级物理课程的核心主题。文章旨在帮助你复习从能量、力到波和电学的基本概念，提供与课堂结构相匹配的清晰解释。利用这份指南巩固理解，自信地准备评估考试。
1. Energy Stores and Transfers | 能量的储存与转移
Energy is the capacity to do work. It is measured in joules (J). A system possesses energy in different stores, such as kinetic energy, gravitational potential energy, thermal energy, chemical energy, elastic potential energy, nuclear energy, and magnetic energy. When a change occurs, energy is transferred between these stores.
能量是做功的能力，以焦耳 (J) 为单位。系统拥有不同形式的能量储存，例如动能、重力势能、热能、化学能、弹性势能、核能和磁能。当发生变化时，能量在这些储存体之间转移。
The law of conservation of energy states that energy cannot be created or destroyed; it can only be transferred from one store to another, or dissipated to the surroundings. For example, when a pendulum swings, gravitational potential energy is converted to kinetic energy and back again, with some energy always transferred to the thermal store of the surroundings due to air resistance and friction at the pivot.
能量守恒定律指出，能量既不能凭空产生也不能凭空消失，只能从一个储存体转移到另一个储存体，或耗散到周围环境。例如，单摆摆动时，重力势能转化为动能，再转化回来，同时部分能量总是通过空气阻力和支点摩擦转移到周围环境的热能储存中。
ul energy transfers are shown with arrows going forward, while wasted energy transfers branch downwards. Sankey diagrams help visualise efficiency, where efficiency = (useful energy output / total energy input) × 100%.
能量转移可利用桑基图表示。每个箭头的宽度与所转移的能量大小成比例。有用的能量转移用向前的箭头表示，浪费的能量则向下分支。桑基图有助于直观理解效率，效率 = (有用的能量输出 / 总能量输入) × 100%。
2. Energy Resources and Electricity Generation | 能源与发电
Energy resources are classified as renewable or non-renewable. Non-renewable resources, such as coal, oil, natural gas, and nuclear fuels, are finite and will eventually run out. Burning fossil fuels releases carbon dioxide, contributing to climate change, while nuclear power produces radioactive waste that requires careful disposal.
能源分为可再生和不可再生两类。不可再生资源（如煤、石油、天然气和核燃料）储量有限，终将耗尽。燃烧化石燃料会释放二氧化碳，加剧气候变化，而核能则产生需谨慎处置的放射性废物。
Renewable energy resources include solar, wind, wave, tidal, hydroelectric, geothermal, and biomass. They can be replenished over a short timescale and generally produce much lower greenhouse gas emissions. However, their output can be variable—for example, solar panels only generate electricity during daylight hours, and wind turbines require sufficient wind speed.
可再生能源包括太阳能、风能、波浪能、潮汐能、水力发电、地热能和生物质能。它们能在短期内再生，通常温室气体排放量低得多。但其输出可能不稳定——例如太阳能电池板仅在白天发电，风力涡轮机需要足够的风速。
In most power stations, a fuel is used to heat water, producing high-pressure steam that drives a turbine connected to a generator. The generator converts kinetic energy into electrical energy via electromagnetic induction. In nuclear power stations, nuclear fission heats the water. In solar cells, light energy is directly converted into electrical energy.
在大多数发电站中，燃料用于加热水，产生高压蒸汽驱动连接发电机的涡轮机。发电机通过电磁感应将动能转化为电能。在核电站中，核裂变加热水；而在太阳能电池中，光能直接转换为电能。
3. Work, Power and Efficiency | 功、功率与效率
In physics, work is done when a force moves an object in the direction of the force. The equation is: W = F × d irection of the force). Work is measured in joules (J). One joule of work is done when a force of one newton moves an object one metre.
在物理学中，当一个力使物体沿力的方向移动时，即做功。公式为：W = F × d（功 = 力 × 沿力方向移动的距离）。功的单位是焦耳 (J)。1 牛顿的力使物体移动 1 米所做的功为 1 焦耳。
Power is the rate at which work is done, or the rate at which energy is transferred. P = W / t J/s. A machine with a high power rating can transfer more energy per second than one with a low power rating.
功率是做功的速率或能量转移的速率。P = W / t（功率 = 做功量 / 时间）。功率的单位是瓦特 (W)，1 W = 1 J/s。高功率的机器每秒钟可比低功率的机器转移更多的能量。
cribes how well a device converts input energy into useful output energy. No device is 100% The efficiency formula is: efficiency = (useful output energy / total input energy) × 100% mproving efficiency reduces wasted energy, saving money and reducing environmental impact.
效率描述设备将输入能量转化为有用输出能量的程度。没有任何设备能达到 100% 的效率，因为总有部分能量以热能形式耗散到周围环境。效率公式为：效率 = (有用的输出能量 / 总输入能量) × 100%。提高效率可减少能源浪费、节约成本并降低环境影响。
4. Forces and Their Effects | 力及其效应
A force is a push or a pull acting upon an object as a result of its interaction with another object. Forces are vector quantities, meaning they have both magnitude and direction. The SI unit of force is the newton (N). Common forces include gravity, friction, air resistance, tension, normal reaction force, and magnetic force.
力是一个物体对另一个物体相互作用而产生的推或拉。力是矢量，既有大小也有方向。力的国际单位是牛顿 (N)。常见的力包括重力、摩擦力、空气阻力、张力、法向反作用力和磁力。
Forces can be represented using free body diagrams; arrows show the direction of each force, with the length proportional to its magnitude. When forces on an object are balanced, the resultant force is zero, and the object remains stationary or moves at a constant velocity. When forces are unbalanced, there is a resultant force causing acceleration in that direction.
力可以用隔离体受力图表示；箭头表示力的方向，长度与其大小成比例。当物体所受的力平衡时，合力为零，物体保持静止或匀速直线运动。当力不平衡时，存在合力，使物体在该方向产生加速度。
Hooke’s Law describes the extension of a spring: F = k × x, where F is the force applied, k is the spring constant, and x is the extension. This linear relationship holds up to the limit of proportionality; beyond this, the spring may be permanently deformed. Elastic materials return to their original shape when the force is removed.
胡克定律描述弹簧的伸长量：F = k × x，其中 F 为施加的力，k 为弹簧常数，x 为伸长量。这种线性关系在比例极限内成立；超过后弹簧可能发生永久形变。弹性材料在撤去外力后能恢复原状。
5. Speed, Velocity and Acceleration | 速率、速度与加速度
Speed is a scalar quantity that measures how fast an object moves, without regard to direction. The average speed is calculated using: v = s / t (speed = distance / time). The standard unit is metres per second (m/s). A distance–time graph has distance on the y‑axis and time on the x‑axis; the gradient represents speed.
速率是一个标量，衡量物体运动的快慢，不考虑方向。平均速率用公式 v = s / t（速率 = 距离 / 时间）计算。标准单位是米每秒 (m/s)。距离–时间图的纵轴为距离，横轴为时间；其斜率表示速率。
Velocity is a vector quantity that describes both speed and direction. An object moving at constant speed but changing direction has a changing velocity, which implies acceleration. Acceleration is the rate of change of velocity: a = Δv / t, where Δv is the change in velocity. It is measured in m/s².
速度是矢量，描述速率和方向。以恒定速率但改变方向运动的物体其速度在变化，这意味着存在加速度。加速度是速度变化的速率：a = Δv / t，其中 Δv 为速度变化量，单位是 m/s²。
On a velocity–time graph, the gradient indicates acceleration, while the area under the graph represents the displacement travelled. A horizontal line shows constant velocity, a straight sloping line shows constant acceleration, and a curved line indicates changing acceleration. Calculating these features allows us to analyse motion in detail.
在速度–时间图中，斜率表示加速度，图线下的面积表示位移。水平线代表匀速直线运动，斜直线代表匀加速运动，曲线则代表加速度在变化。通过计算这些特征可以详细分析运动。
6. Gravity, Mass and Weight | 重力、质量与重量
Mass is a measure of the amount of matter in an object. It is a scalar quantity and remains constant regardless of location. The SI unit of mass is the kilogram (kg). Weight is the force acting on a mass due to gravity; it is a vector quantity measured in newtons (N).
质量是物体所含物质的量度，是标量，不随位置改变而改变。质量的国际单位是千克 (kg)。重量是作用在质量上的重力，为矢量，单位是牛顿 (N)。
The relationship between weight and mass is: W = m × g ften used for calculations. The value of g is different on other planets and decreases with altitude above Earth’s surface.
重量和质量的关系为：W = m × g，其中 W 为重量，m 为质量，g 为重力场强度。在地球上，g 约等于 9.8 N/kg，计算中常取 10 N/kg。其他行星上的 g 值不同，并且随离地面高度的增加而减小。
An object’s weight can be measured using a force meter (spring balance). Weight causes objects to fall towards the centre of the Earth. In the absence of air resistance, all objects fall with the same acceleration (g). Air resistance acts opposite to the direction of motion, eventually causing a falling object to reach terminal velocity when forces balance.
物体的重量可用测力计（弹簧秤）测量。重力使物体落向地球中心。若无空气阻力，所有物体将以相同的加速度 (g) 下落。空气阻力与运动方向相反，最终使下落的物体达到收尾速度，此时受力平衡。
7. Electric Circuits: Current and Voltage | 电路：电流与电压
Electric current is the rate of flow of electric charge. It is measured in amperes (A). In a metal wire, current is the movement of free electrons from the negative terminal to the positive terminal, although conventional current flows from positive to negative. The equation linking charge and current is: Q = I × t, where Q is charge in coulombs (C), I is current, and t is time in seconds.
电流是电荷流动的速率，单位是安培 (A)。在金属导线中，电流是自由电子从负极向正极移动的过程，但常规电流方向是从正极到负极。电荷与电流的关系为：Q = I × t，其中 Q 为电荷量（库仑，C），I 为电流，t 为时间（秒）。
Voltage (potential difference) is the energy transferred per unit charge between two points. It is measured in volts (V). One volt means one joule of energy transferred per coulomb of charge. The equation is: V = W / Q or E = Q × V. A battery or power supply provides the potential difference that pushes charge around a circuit.
电压（电势差）是单位电荷在两点间转移的能量，单位是伏特 (V)。1 伏特表示每库仑电荷转移 1 焦耳能量。公式为：V = W / Q 或 E = Q × V。电池或电源提供电势差，推动电荷在电路中流动。
Current is measured using an ammeter connected in series, while potential difference is measured using a voltmeter connected in parallel. In a series circuit, the current is the same at all points, but the supply voltage is shared between components. In a parallel circuit, the current splits at junctions, and each branch receives the full supply voltage.
测量电流用串联电流表，测量电压用并联电压表。在串联电路中，各处电流相等，但总电压分配给各元件。在并联电路中，电流在节点处分流，每条支路都获得全部电源电压。
8. Resistance and Ohm’s Law | 电阻与欧姆定律
Resistance is a measure of how much a component opposes the flow of electric current. It is measured in ohms (Ω). Resistance depends on the material, length, cross-sectional area, and temperature of the conductor. A longer wire has higher resistance; a thicker wire has lower resistance.
电阻衡量元件对电流阻碍作用的大小，单位是欧姆 (Ω)。电阻取决于导体的材料、长度、横截面积和温度。长度越长，电阻越大；横截面积越大，电阻越小。
Ohm’s Law states that, for a metallic conductor kept at constant temperature, the current through it is directly proportional to the potential difference across it: V = I × R. Components that obey this law are called ohmic conductors; their current–voltage graph is a straight line passing through the origin. Components such as diodes and filament lamps are non-ohmic.
欧姆定律指出，对于保持恒温的金属导体，通过它的电流与两端的电势差成正比：V = I × R。遵循此定律的元件称为欧姆导体，其电流–电压图是通过原点的直线。而二极管、白炽灯等元件是非欧姆的。
For resistors in series, the total resistance is the sum of individual resistances: Rtotal = R₁ + R₂ + .... For resistors in parallel, the total resistance is less than the smallest individual resistance and can be found using 1/Rtotal = 1/R₁ + 1/R₂ + .... Adding resistors in parallel provides additional paths, reducing total resistance and increasing current.
串联电阻的总电阻为各电阻之和：R总 = R₁ + R₂ + ...。并联电阻的总电阻小于最小单个电阻，计算公式为 1/R总 = 1/R₁ + 1/R₂ + ...。并联电阻增加了电流路径，使总电阻减小、总电流增大。
9. Waves: Longitudinal and Transverse | 波：纵波与横波
Waves transfer energy from one place to another without transferring matter. There are two main types: transverse and longitudinal. In transverse waves, the oscillations are perpendicular to the direction of energy transfer. Examples include water waves, waves on a string, and all electromagnetic waves.
波将能量从一处传递到另一处而不传递物质。波主要有两种类型：横波和纵波。在横波中，振动方向与能量传递方向垂直。例如水波、弦上的波以及所有电磁波。
In longitudinal waves, the oscillations are parallel to the direction of energy transfer. These waves consist of compressions (regions of high pressure) and rarefactions (regions of low pressure). Sound waves in air are longitudinal. The particles vibrate back and forth along the direction the wave travels, creating alternating regions of compression and rarefaction.
在纵波中，振动方向与能量传递方向平行。这类波由密部（高压区）和疏部（低压区）组成。空气中的声波是纵波。粒子沿着波传播方向来回振动，形成交替的密部和疏部。
The key features of a wave include wavelength (λ), frequency (f), amplitude, and wave speed (v). The wave equation links these: v = f × λ. Frequency is measured in hertz (Hz), meaning cycles per second. Amplitude is the maximum displacement from the rest position and relates to the energy carried by the wave.
波的主要特征包括波长 (λ)、频率 (f)、振幅和波速 (v)。波动方程将它们联系起来：v = f × λ。频率的单位是赫兹 (Hz)，即每秒周期数。振幅是离开平衡位置的最大位移，与波携带的能量有关。
10. Sound Waves and Hearing | 声波与听觉
Sound travels as a longitudinal wave, requiring a medium such as solid, liquid, or gas; it cannot travel through a vacuum. The speed of sound in air at room temperature is approximately 340 m/s. Sound travels faster in solids than in liquids, and faster in liquids than in gases, because particles are closer together and can pass on vibrations more rapidly.
声音以纵波形式传播，需要固体、液体或气体等介质；真空中无法传声。室温下空气中的声速约为 340 m/s。声音在固体中比在液体中传播得快，在液体中比在气体中快，因为粒子间距更近，能更快传递振动。
The pitch of a sound is determined by its frequency; a high-frequency wave produces a high-pitched sound, while a low-frequency wave produces a low-pitched sound. The loudness of a sound relates to the amplitude of the wave; larger amplitude means louder sound. Humans can typically hear frequencies from about 20 Hz to 20 kHz. Frequencies above this range are ultrasound.
声音的音调由频率决定；高频波产生高音调，低频波产生低音调。声响度与波的振幅有关；振幅越大，声音越响。人类通常可听到的频率范围约 20 Hz 到 20 kHz。高于此范围的频率为超声波。
Sound waves can be reflected, forming echoes. The reflection of sound follows the law of reflection: the angle of incidence equals the angle of reflection. Ultrasound has many applications, including medical imaging (scanning foetuses), industrial cleaning, and sonar for measuring the depth of water or detecting objects underwater.
声波可发生反射形成回声。声波的反射遵循反射定律：入射角等于反射角。超声波有许多应用，包括医学成像（胎儿扫描）、工业清洁以及用于测量水深或探测水下物体的声呐。
11. Light and the Electromagnetic Spectrum | 光与电磁波谱
⁸ m/s. When light strikes a surface, it can be reflected, transmitted, or absorbed. The law of reflection applies to smooth surfaces; rough surfaces cause diffuse reflection, scattering light in many directions.
光是一种横波电磁波，能在真空中以约 3.0 × 10⁸ m/s 的速度传播。光照射到表面时可被反射、透射或吸收。光滑表面遵循反射定律；粗糙表面发生漫反射，将光散射到各个方向。
Refraction is the bending of light when it passes from one transparent medium to another, due to a change in speed. When light enters a denser medium, it slows down and bends towards the normal; when it enters a less dense medium, it speeds up and bends away from the normal. Lenses use refraction to converge or diverge light rays.
折射是光从一种透明介质进入另一种介质时，由于速度变化而发生弯折的现象。光进入密度较大的介质时速度减小，向法线偏折；进入密度较小的介质时速度增大，远离法线偏折。透镜利用折射会聚或发散光线。
The electromagnetic spectrum is a continuous range of waves ordered by frequency and wavelength. From longest wavelength/lowest frequency to shortest/highest, the main regions are: radio waves, microwaves, infrared, visible light, ultraviolet, X‑rays, and gamma rays. All travel at the same speed in a vacuum but have different properties and uses. For instance, infrared is used for thermal imaging, and X‑rays for medical imaging.
电磁波谱是按频率和波长排列的连续波谱。从波长最长/频率最低到波长最短/频率最高，主要区域为：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速度相同，但性质与用途各异。例如，红外线用于热成像，X 射线用于医学影像。
12. The Particle Model and Pressure | 粒子模型与压力
All matter is made up of tiny particles. The particle model describes the arrangement, movement, and energy of these particles in solids, liquids, and gases. In solids, particles vibrate in fixed positions, giving a definite shape and volume. In liquids, particles are close but can move past each other, so they take the shape of the container but have a fixed volume. In gases, particles are far apart and move rapidly, filling any available space.
所有物质均由微小粒子组成。粒子模型描述了固体、液体和气体中粒子的排列、运动和能量。固体中粒子在固定位置振动，具有确定的形状和体积。液体中粒子排列紧密但可相互滑动，因此呈容器形状但体积固定。气体中粒子相距较远且快速运动，充满所有可用空间。
Density is the mass per unit volume of a substance: ρ = m / V, where ρ is density, m is mass, and V is volume. The unit is kg/m³. Solids generally have high densities because particles are tightly packed; gases have very low densities. The density of a regularly shaped solid can be found by measuring its mass and calculating volume from its dimensions.
密度是物质单位体积的质量：ρ = m / V，其中 ρ 为密度，m 为质量，V 为体积，单位是 kg/m³。固体因粒子紧密排列通常密度较高；气体密度很低。规则形状固体的密度可通过测量质量并结合尺寸计算体积来求得。
Changes of state occur when a substance is heated or cooled. Melting and boiling absorb energy without temperature change; freezing and condensing release energy. The temperature at which these changes occur are the melting point and boiling point. The particle model helps explain these: during melting, particles gain enough energy to break free from fixed positions.
物质受热或冷却时发生物态变化。熔化和沸腾时吸收能量而温度不变；凝固和冷凝时释放能量。发生这些变化时的温度即熔点和沸点。粒子模型有助于解释：熔化时粒子获得足够能量脱离固定位置。
Gas pressure is caused by particles colliding with the walls of a container. Increasing temperature increases the average kinetic energy of the particles, making collisions more frequent and more forceful, thereby raising the pressure (at constant volume). At a constant temperature, reducing the volume of a gas increases pressure because particles hit the walls more often. This is described by the relationship p × V = constant for a fixed mass of gas at constant temperature.
气体压强由粒子碰撞容器壁产生。温度升高使粒子的平均动能增大，碰撞更频繁、更有力，从而增大压强（体积一定时）。在恒温下，减小气体体积会使压强升高，因为粒子更频繁地撞击壁面。这由固定质量气体在恒温下的关系 p × V = 常量 描述。
Published by TutorHao | Physics Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图