📚 Year 8 WJEC Physics: Core Knowledge Review | Year 8 WJEC 物理：核心知识点梳理
This article summarises the essential topics covered in the Year 8 WJEC Physics curriculum. It provides a clear and structured overview of energy, forces, electricity, waves, matter, and space, helping you consolidate your learning and prepare effectively for assessments. Each section pairs English explanations with Chinese translations, ensuring you grasp key concepts in both languages.
本文梳理了 Year 8 WJEC 物理课程的核心知识点，涵盖能量、力、电、波、物质和空间等重要主题。文中每个要点都采用英文和中文配对讲解，帮助你巩固学习，为考试做好充分准备。
1. Energy Forms and Stores | 能量的形式与储存
Energy is never created or destroyed; it is stored in different ways. The main energy stores include kinetic (movement), thermal (heat), chemical (in fuels and food), elastic potential (stretched or compressed objects), gravitational potential (height of an object), and nuclear (inside atoms).
能量既不会凭空产生也不会凭空消失，它以多种形式储存起来。主要的能量储存形式包括动能（运动）、热能（热量）、化学能（燃料和食物中）、弹性势能（拉伸或压缩的物体）、重力势能（物体的高度）以及核能（原子内部）。
An object can have more than one energy store at the same time. For example, a moving car has kinetic energy, but also chemical energy in its fuel and thermal energy in the engine.
一个物体可以同时具有多种能量储存。例如，行驶中的汽车既有动能，其燃料中还储存着化学能，发动机内还包含热能。
Energy is measured in joules (J). A kilojoule (kJ) is 1000 J. The larger the energy store, the greater its ability to do work.
能量的单位是焦耳 (J)。1 千焦 (kJ) 等于 1000 J。储存的能量越多，做功的能力就越强。
2. Energy Transfers and Conservation | 能量的转移与守恒
Whenever something changes, energy is transferred from one store to another. These transfers can happen through heating, doing work using a force, or by electric currents. A toaster, for instance, transfers electrical energy to thermal energy.
每当发生某种变化时，能量就会从一个储存转移到另一个储存。能量的转移可以通过加热、通过力做功或通过电流来实现。例如，烤面包机将电能转化为热能。
The total amount of energy before and after any transfer is always the same. This is the law of conservation of energy. In every transfer, some energy is almost always dissipated (spread out) as thermal energy and becomes less useful.
任何转移前后，能量的总量始终不变。这就是能量守恒定律。在每次转移过程中，总有一部分能量以热能的形式耗散（散发出去），变得不再那么有用。
We can show energy transfers using simple diagrams or Sankey diagrams. Sankey diagrams use arrows whose widths represent the amount of energy; the input arrow and the useful and wasted output arrows add up to the same total.
我们可以用简单的图示或桑基图来表示能量的转移。桑基图用箭头的宽度代表能量的多少；输入箭头代表的总能量等于有用输出与浪费输出之和。
3. Forces and Their Effects | 力及其作用效果
A force is a push or a pull acting on an object. Forces are measured in newtons (N). They can cause an object to speed up, slow down, change direction, or change shape. Gravity, friction, air resistance, and upthrust are all forces.
力是作用在物体上的推力或拉力，单位是牛顿 (N)。力可以使物体加速、减速、改变方向或改变形状。重力、摩擦力、空气阻力和浮力都是常见的力。
Forces usually act in pairs. When you sit on a chair, your weight pushes down on the chair, and the chair pushes back up on you with an equal and opposite reaction force.
力通常成对出现。当你坐在椅子上时，你的体重向下压椅子，椅子同时向上给你一个大小相等、方向相反的支持力。
Friction is a force that opposes motion. It can be useful, such as when it allows tyres to grip the road, but it can also be a problem, causing moving parts to wear out and produce unwanted heat.
摩擦力是阻碍运动的力。它有时很有用，比如让车胎抓紧路面；但有时也会带来麻烦，使运动部件磨损并产生不需要的热量。
4. Speed and Motion | 速度与运动
Speed tells us how quickly an object is moving. It can be calculated using:
average speed = distance ÷ time
速度表示物体运动的快慢。可用下式计算：
平均速度 = 距离 ÷ 时间
If a cyclist travels 300 metres in 30 seconds, their average speed is 10 m/s. The unit of speed depends on the units of distance and time, for example metres per second (m/s) or kilometres per hour (km/h).
如果一名自行车手在 30 秒内骑行了 300 米，其平均速度就是 10 m/s。速度的单位取决于距离和时间的单位，如米每秒 (m/s) 或千米每小时 (km/h)。
A distance–time graph shows how an object moves. A straight horizontal line means the object is stationary; a straight sloping line shows constant speed; a steeper line indicates a faster speed.
距离-时间图能展示物体的运动情况。水平直线表示物体静止；倾斜直线表示匀速运动；线条越陡，速度越快。
5. Electric Circuits: Series and Parallel | 串联电路与并联电路
An electric circuit must be complete for a current to flow. It consists of a power supply (battery), wires, and components such as bulbs, buzzers, or motors. The current is the flow of electric charge, measured in amperes (A).
电路必须闭合才能形成电流。它由电源（电池）、导线以及灯泡、蜂鸣器或电动机等元件组成。电流是电荷的流动，单位是安培 (A)。
In a series circuit, there is only one loop. The current is the same everywhere, but the lamps share the voltage from the battery, so adding more lamps makes each one dimmer. If one component breaks, the whole circuit stops working.
在串联电路中，只有一条回路。各处的电流大小相同，但灯泡会分担电池的电压，因此增加灯泡会使每个灯泡变暗。一旦某个元件损坏，整个电路就会中断。
In a parallel circuit, there are multiple loops. The voltage across each branch is the same as the battery voltage, so lamps stay bright. If one lamp goes out, the others can still work. Parallel circuits are used in most home lighting systems.
在并联电路中，存在多条支路。每条支路的电压与电池电压相同，因此灯泡能保持明亮。即使一盏灯熄灭，其他灯仍能正常工作。大部分家庭照明都采用并联电路。
6. Current, Voltage and Resistance | 电流、电压与电阻
Current (I) is the rate of flow of charge. Voltage (V) is the push that drives the current around the circuit. Resistance (R) is a measure of how difficult it is for the current to flow, measured in ohms (Ω).
电流 (I) 是电荷流动的速率。电压 (V) 是驱动电流在电路中流动的推力。电阻 (R) 衡量电流流动的难易程度，单位是欧姆 (Ω)。
As resistance increases, the current decreases if the voltage stays the same. Ohm's law is often stated as:
V = I × R
在电压不变的情况下，电阻增大，电流就会减小。欧姆定律常表示为：
V = I × R
Thin or long wires have higher resistance than thick or short wires. Components such as resistors are designed to provide a specific resistance to control current in a circuit.
细长导线的电阻比粗短导线大。电阻器等元件被设计来提供特定的电阻，以控制电路中的电流。
7. Sound Waves | 声波
Sound is produced by vibrations that travel through a medium (solid, liquid, or gas) as longitudinal waves. In a longitudinal wave, the particles vibrate back and forth in the same direction as the wave travels, forming compressions and rarefactions.
声音是由振动产生的，并以纵波的形式通过介质（固体、液体或气体）传播。在纵波中，粒子的振动方向与波的传播方向相同，形成疏密相间的压缩区和稀疏区。
Sound cannot travel through a vacuum because there are no particles to pass on vibrations. This is why astronauts on the Moon cannot hear each other directly and must use radio equipment.
声音不能在真空中传播，因为没有粒子传递振动。这就是为什么月球上的宇航员不能直接听到彼此的声音，必须使用无线电设备。
Pitch depends on frequency (the number of vibrations per second, measured in hertz, Hz). A high frequency gives a high pitch. Loudness depends on the amplitude of the wave: larger amplitude means a louder sound.
音调取决于频率（每秒振动的次数，单位是赫兹 Hz）。频率高则音调高。响度取决于波的振幅：振幅越大，声音越响。
8. Light and Reflection | 光与反射
Light travels in straight lines at a speed of about 300 000 000 m/s in a vacuum. It can be reflected, refracted, or absorbed. When light bounces off a flat mirror, the angle of incidence equals the angle of reflection.
光在真空中沿直线传播，速度约为 3×10⁸ 米/秒。光可以被反射、折射或吸收。当光射到平面镜上时，反射角等于入射角。
The incident ray, the reflected ray, and the normal (an imaginary line perpendicular to the mirror) all lie in the same plane. This is called the law of reflection.
入射光线、反射光线和法线（垂直于镜面的假想线）位于同一平面内，这就是反射定律。
White light is a mixture of all the colours of the visible spectrum. When it passes through a prism, it is dispersed into the colours red, orange, yellow, green, blue, indigo, and violet (ROYGBIV).
白光是由可见光谱中所有颜色的光混合而成的。当白光通过棱镜时，会被分散成红、橙、黄、绿、蓝、靛、紫 (ROYGBIV) 七种颜色。
9. The Particle Model of Matter | 物质的粒子模型
All matter is made up of tiny particles that are constantly moving. The arrangement and movement of these particles determine whether a substance is a solid, liquid, or gas.
所有物质都由不断运动的微小粒子组成。粒子的排列方式和运动情况决定了物质是固体、液体还是气体。
| State | Arrangement | Movement |
|---|---|---|
| Solid | Regular pattern, closely packed | Vibrate in fixed positions |
| Liquid | Random, close together | Move around each other |
| Gas | Random, far apart | Move quickly in all directions |
加热物质时，粒子获得更多动能，运动加快，导致物质体积膨胀或发生物态变化。物质从固态变为液态的过程称为熔化，从液态变为气态称为沸腾或蒸发。
When substances are cooled, particles lose kinetic energy and move closer together. This is why solids generally contract when cooled, and gases can condense into liquids.
当物质被冷却时，粒子失去动能，彼此靠得更近。这就是固体遇冷通常会收缩，而气体能凝结成液体的原因。
Density describes how much mass is packed into a given volume. Solids usually have the highest density because particles are packed tightly. Density is calculated by:
density = mass ÷ volume
密度描述单位体积内所含质量的大小。由于粒子排列紧密，固体通常密度最高。密度计算公式为：
密度 = 质量 ÷ 体积
10. Magnets and Electromagnets | 磁铁与电磁铁
A magnet has two poles, north and south. Like poles repel each other, and unlike poles attract. The region around a magnet where it exerts a force is called a magnetic field, shown by field lines going from north to south.
磁铁有两个磁极：北极和南极。同名磁极相互排斥，异名磁极相互吸引。磁铁周围产生力的区域称为磁场，用从北极指向南极的磁感线来表示。
A compass is a small bar magnet that aligns itself with Earth's magnetic field. Its north pole points toward Earth's magnetic north pole.
指南针是一个小磁条，会与地球磁场方向对齐。它的北极指向地球的磁北极。
An electromagnet is made by wrapping a coil of wire around an iron core and passing an electric current through it. Its magnetism can be turned on and off; it is much stronger when the current is larger or when the coil has more turns. Electromagnets are used in scrapyard cranes, electric bells, and relays.
电磁铁是将线圈缠绕在铁芯上并通以电流制成的。它的磁性可以随时开启和关闭；电流越大或线圈匝数越多，磁性就越强。电磁铁常用于废料厂起重机、电铃和继电器中。
11. The Solar System and Seasons | 太阳系与季节
Our solar system consists of the Sun, eight planets, dwarf planets, moons, asteroids, and comets. The planets are held in orbit by the gravitational pull of the Sun. In order from the Sun, they are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
太阳系由太阳、八大行星、矮行星、卫星、小行星和彗星组成。行星在太阳的引力作用下沿轨道运行。按照离太阳由近到远的顺序，依次是水星、金星、地球、火星、木星、土星、天王星和海王星。
The Earth rotates on its axis once every 24 hours, giving us day and night. It orbits the Sun in about 365.25 days, which is one year. The tilt of Earth's axis causes the seasons, as different parts of the planet receive varying amounts of sunlight throughout the year.
地球每 24 小时自转一圈，形成了昼夜交替。它绕太阳公转一圈约为 365.25 天，也就是一年。地轴的倾斜导致了季节变化，因为一年中地球不同区域接收到的太阳光照量不同。
During summer in the northern hemisphere, the North Pole tilts toward the Sun, resulting in longer days and warmer temperatures. In winter, it tilts away, making days shorter and colder.
北半球夏季时，北极向太阳倾斜，导致白昼更长、气温更高。冬季时，北极远离太阳，白昼变短，天气变冷。
12. Heat Transfer: Conduction, Convection and Radiation | 热传递：传导、对流和辐射
Thermal energy is transferred from hotter regions to cooler regions by three processes: conduction, convection, and radiation. Conduction happens mainly in solids, where vibrating particles pass on energy to neighbours. Metals are excellent conductors because they have free electrons that help transfer heat quickly.
热能通过三种方式从高温区域传递到低温区域：传导、对流和辐射。传导主要发生在固体中，振动的粒子将能量传递给相邻的粒子。金属是优良的导体，因为它们拥有自由电子，能迅速传递热量。
Convection occurs in fluids (liquids and gases). When a fluid is heated, it expands, becomes less dense, and rises. Cooler, denser fluid sinks to take its place, setting up a convection current. This is what transfers heat in a pot of water or in the air above a radiator.
对流发生在流体（液体和气体）中。流体受热后膨胀，密度变小而上升。较冷、密度较大的流体下沉补充，形成对流。这就是锅中水和散热器上方空气传递热量的原理。
Radiation is the transfer of energy by infrared waves. It does not require particles and can travel through a vacuum, which is how the Sun's heat reaches Earth. Dark, matt surfaces are good absorbers and emitters of radiation, while shiny, light surfaces reflect it.
辐射是通过红外波进行的能量传递。它不需要粒子，可以在真空中传播，这正是太阳热量到达地球的方式。暗色、粗糙的表面是辐射的良好吸收体和发射体，而光亮、浅色的表面则能反射辐射。
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