📚 Core Topics Revision for Year 7 WJEC Physics | Year 7 WJEC 物理：核心知识点梳理
Welcome to your Year 7 WJEC Physics revision guide. This article brings together all the essential topics you need to master, from forces and energy to electricity, waves and the particle model. Each section is presented in a clear bilingual format to help you build understanding and confidence in both English and Chinese. Let us start strengthening your physics foundations right now.
欢迎阅读 Year 7 WJEC 物理复习指南。本文汇集了你必须掌握的所有核心知识点，从力、能量到电学、波和粒子模型。每个部分都以清晰的双语对照形式呈现，帮助你用中英双语建立理解和信心。现在就开始夯实你的物理基础吧。
1. Understanding Forces | 认识力
A force is a push or a pull acting on an object. Forces can change the speed, direction or shape of something. They are measured in newtons (N) using a force meter.
力是作用在物体上的推或拉。力可以改变物体的速度、方向或形状。力用牛顿 (N) 作单位，可用测力计测量。
Forces often occur in pairs. When you sit on a chair, your weight pushes down on the chair and the chair pushes back up on you. This is called an interaction pair.
力往往成对出现。当你坐在椅子上时，你的体重向下压椅子，椅子同时向上推你。这称为相互作用力对。
force (N) = mass (kg) × acceleration (m/s²)
We can represent forces using arrows in free-body diagrams. The length of the arrow shows the size of the force, and the arrowhead shows the direction.
我们可以用受力图中的箭头来表示力。箭头的长度表示力的大小，箭头指向表示力的方向。
2. Gravity and Weight | 重力与重量
Gravity is a force that pulls objects towards the centre of the Earth. It gives everything weight. Weight is not the same as mass – mass is the amount of matter in an object and stays the same everywhere, while weight depends on gravity.
重力是把物体拉向地球中心的力，它使一切物体有重量。重量不等于质量——质量是物体所含物质的多少，在任何地方都不变，而重量取决于重力。
On Earth, the gravitational field strength is about 10 N/kg. This means a 1 kg mass has a weight of 10 N. You can calculate weight using the simple equation:
地球表面的引力场强度约为 10 N/kg。这意味着 1 kg 的质量重量为 10 N。你可以用这个简单公式计算重量：
weight (N) = mass (kg) × gravitational field strength (N/kg)
If you travel to the Moon, your mass would be unchanged but your weight would be much smaller because the Moon's gravity is weaker.
如果你去到月球，你的质量不变，但重量会小得多，因为月球引力更弱。
3. Friction and Air Resistance | 摩擦与空气阻力
Friction is a force that opposes motion between two surfaces in contact. It can be useful (like when you walk without slipping) or a nuisance (causing parts to wear out).
摩擦力是阻碍两个接触表面相对运动的力。它可能有用（如让你走路时不滑倒），也可能带来麻烦（导致部件磨损）。
Air resistance is a type of friction that acts on objects moving through air. The faster an object moves, the greater the air resistance. Streamlined shapes reduce air resistance, which helps cars and cyclists go faster.
空气阻力是摩擦的一种，作用于在空气中运动的物体。物体运动越快，空气阻力越大。流线型可以减少空气阻力，帮助汽车和自行车手跑得更快。
When a skydiver jumps from a plane, gravity pulls them down while air resistance pushes up. Eventually these forces balance and the skydiver reaches terminal velocity.
跳伞者从飞机跳下时，重力向下拉，空气阻力向上推。最终这两个力平衡，跳伞者达到终极速度。
4. Energy: Forms and Stores | 能量：形式与储存
Energy is the ability to do work. It is measured in joules (J). Energy can be stored in many ways. In Year 7 you will come across these main stores: chemical energy (in food and batteries), kinetic energy (in moving objects), gravitational potential energy (in objects raised above the ground), elastic potential energy (in stretched springs), thermal energy (heat), and nuclear energy.
能量是做功的本领，单位是焦耳 (J)。能量可以多种形式储存。Year 7 你会接触到这些主要的能量储存：化学能（食物和电池中）、动能（运动的物体）、重力势能（被举高的物体）、弹性势能（拉伸的弹簧）、热能以及核能。
A moving car has kinetic energy. A book on a high shelf has gravitational potential energy. When the book falls, its gravitational potential energy is converted into kinetic energy.
行驶的汽车具有动能。放在高处书架上的书具有重力势能。书下落时，它的重力势能转化为动能。
Energy cannot be created or destroyed, only transferred from one store to another. This is the law of conservation of energy.
能量不会凭空产生或消失，只能从一个储存转移到另一个储存。这就是能量守恒定律。
5. Energy Transfers and Efficiency | 能量转移与效率
Energy can be transferred by four main pathways: mechanical work (a force moving an object), heating (because of a temperature difference), electrical work (current flowing), and radiation (light or sound waves).
能量可通过四种主要途径转移：机械做功（力移动物体）、加热（由于温度差）、电做功（电流流动）以及辐射（光波或声波）。
In any energy transfer, some energy is almost always dissipated as thermal energy, which spreads out and becomes less useful. Sankey diagrams are used to show the energy transfers, with the arrow widths representing the amount of energy.
在任何能量转移中，几乎总有一部分能量作为热能散失掉，扩散出去后变得不那么有用。Sankey 图用来展示能量转移，箭头的宽度代表能量的多少。
Efficiency tells us how much of the input energy is transferred usefully. A more efficient device wastes less energy. In Year 7 you may use simple comparisons rather than numerical calculations.
效率告诉我们输入能量中有多少被有效利用。效率更高的设备浪费的能量更少。Year 7 阶段你可能进行简单比较，而不做数值计算。
6. Electric Current and Simple Circuits | 电流与简单电路
An electric current is a flow of electric charge, usually carried by electrons moving through a wire. For a current to flow, we need a complete circuit and a source of potential difference, such as a cell or battery.
电流是电荷的流动，通常由电子在导线中移动形成。要让电流流动，我们需要一个完整的电路和一个电势差来源，如电池。
Current is measured in amperes (A) using an ammeter connected in series. Voltage (potential difference) is measured in volts (V) using a voltmeter connected in parallel.
电流用安培 (A) 作单位，用串联的安培表测量。电压（电势差）以伏特 (V) 为单位，用并联的伏特表测量。
In a series circuit, there is only one loop and the current is the same everywhere. In a parallel circuit, the current splits between the branches but the voltage across each branch is the same.
串联电路只有一个回路，各处电流相等。并联电路中电流在各支路间分流，但各支路两端电压相同。
7. Circuit Components and Symbols | 电路元件与符号
You need to recognise standard circuit symbols: a cell, a battery, a bulb, a switch, a buzzer, a motor, a resistor, and a variable resistor. Drawing clear circuit diagrams is a key skill.
你需要认识标准的电路符号：电池、电池组、灯泡、开关、蜂鸣器、电动机、电阻和可变电阻。能画出清晰的电路图是一项重要技能。
A switch controls whether current can flow. When the switch is open, the circuit is broken and no current flows. A resistor limits the current. Adding more bulbs in series makes them dimmer because the total resistance increases.
开关控制电流是否通过。开关断开时，电路不通，没有电流。电阻限制电流。串联更多灯泡会使它们变暗，因为总电阻增大了。
Conductors let electricity pass easily (e.g., copper), while insulators do not (e.g., plastic). The metal part of a wire is the conductor, and the plastic coating is the insulator.
导体容易让电流通过（如铜），绝缘体则不然（如塑料）。导线中的金属部分是导体，塑料外皮是绝缘体。
8. Sound Waves | 声波
Sound is produced by vibrating objects. These vibrations travel through a medium (solid, liquid or gas) as longitudinal waves. Sound cannot travel through a vacuum because there are no particles to carry the vibration.
声音由振动的物体产生。这些振动通过介质（固体、液体或气体）以纵波的形式传播。声音不能在真空中传播，因为没有粒子传递振动。
The loudness of a sound depends on the amplitude of the wave. The pitch depends on the frequency. A high-pitched sound has a higher frequency (more waves per second).
声音的响度取决于声波的振幅。音调高低取决于频率。高音调的声音频率更高（每秒波数更多）。
Humans can hear sounds in the frequency range roughly from 20 Hz to 20 000 Hz. Sound travels faster in solids than in liquids, and faster in liquids than in gases.
人类大致能听到 20 Hz 到 20 000 Hz 频率范围内的声音。声音在固体中传播最快，液体中次之，气体中最慢。
9. Light: Reflection and Shadows | 光：反射与影子
Light travels in straight lines. We see objects because light from a source reflects off them into our eyes. A shadow is formed when an opaque object blocks the path of light.
光沿直线传播。我们之所以看见物体，是因为光源发出的光从物体反射进入我们的眼睛。不透明的物体挡住光的去路时就会形成影子。
When light hits a smooth surface like a plane mirror, it reflects according to the law of reflection: the angle of incidence equals the angle of reflection. Both angles are measured from the normal, an imaginary line perpendicular to the mirror surface.
当光射到平面镜这种光滑表面时，会根据反射定律进行反射：入射角等于反射角。这两个角都从法线（垂直于镜面的虚线）算起。
Transparent materials allow light to pass through clearly; translucent materials let some light through but scatter it; opaque materials do not let light through at all.
透明材料允许光线清晰透过；半透明材料可以让部分光线通过但发生散射；不透明材料则完全不让光线通过。
10. The Particle Model of Matter | 物质的粒子模型
All matter is made up of tiny particles (atoms or molecules) that are constantly moving. The particle model helps explain the properties of solids, liquids and gases.
所有物质都由不断运动的微小粒子（原子或分子）构成。粒子模型可以帮助解释固体、液体和气体的性质。
In solids, particles are packed closely together in a fixed arrangement and can only vibrate on the spot. This gives solids a fixed shape and volume.
在固体中，粒子紧密排列、位置固定，只能原地振动。因此固体有固定的形状和体积。
In liquids, particles are still close but can slide past each other, so liquids have a fixed volume but take the shape of their container. In gases, particles are far apart and move randomly at high speeds, so gases have no fixed shape or volume and can be compressed.
在液体中，粒子仍靠近但能互相滑动，因此液体有固定体积但形状随容器而变。在气体中，粒子相距很远且快速无规则运动，所以气体没有固定的形状和体积，且可被压缩。
11. Changes of State | 物态变化
When a substance is heated, its particles gain kinetic energy. Melting (solid to liquid) and boiling or evaporation (liquid to gas) are endothermic processes – they take in energy. Freezing and condensation are the reverse changes and release energy.
物质受热时，其粒子获得动能。熔化（固态变液态）和沸腾或蒸发（液态变气态）是吸热过程——它们吸收能量。凝固和凝结则是相反的过程，会释放能量。
The melting point and boiling point of a pure substance are fixed at a given pressure. Water, for example, melts at 0 °C and boils at 100 °C at standard pressure.
纯净物在给定压强下的熔点和沸点是固定的。例如，在标准压强下水的熔点是 0 °C，沸点是 100 °C。
Evaporation can happen at any temperature and occurs only at the surface of a liquid. Boiling occurs throughout the liquid at a specific temperature.
蒸发可以在任何温度下发生，且只发生在液体表面。沸腾则是在某一特定温度下，整个液体内部同时发生的汽化现象。
12. The Solar System and Beyond | 太阳系及更远
Our Solar System consists of the Sun, eight planets, their moons, and smaller objects like asteroids and comets. The Sun is a star, a huge ball of hot gas that produces light and heat through nuclear fusion.
我们的太阳系包括太阳、八大行星、它们的卫星以及小行星和彗星等较小的天体。太阳是一颗恒星，是一个通过核聚变产生光和热的巨大炽热气体球。
The planets in order from the Sun are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The first four are rocky planets; the outer four are gas giants.
按离太阳由近到远的顺序，行星为水星、金星、地球、火星、木星、土星、天王星和海王星。前四颗是岩石行星，外面四颗是气态巨行星。
Gravity keeps planets in orbit around the Sun and moons in orbit around planets. A year is the time a planet takes to orbit the Sun once, and a day is the time it takes to spin once on its axis.
引力使行星绕太阳公转，也使卫星绕行星公转。一年是行星绕太阳公转一周的时间，一天是行星自转一周的时间。
Published by TutorHao | Physics Revision Series | aleveler.com
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