📚 Year 9 WJEC Physics: Vocabulary & Terminology Quick-Memory Guide | Year 9 WJEC 物理：词汇术语速记指南
Building a strong command of scientific vocabulary is the foundation of success in Year 9 WJEC Physics. This guide breaks down the essential terms you will encounter in topics like forces, energy, waves, electricity, and more. Each key word is explained in plain English with a matching Chinese translation, plus clever memory hooks to help you retain them for exams and practical work.
熟练掌握科学词汇是九年级 WJEC 物理取得好成绩的基础。本指南逐项拆解力、能量、波、电等主题中的核心术语。每个关键词都用简明英文解释并配以中文翻译，还加入了巧妙的记忆挂钩，帮助你在考试和实验中牢牢记住它们。
1. Forces and Motion | 力与运动
A force is a push or a pull acting on an object. Forces can change an object's shape, speed, or direction of motion. They are measured in newtons (N). Remember: a newton is roughly the weight of a small apple – it is the force needed to accelerate 1 kg by 1 m/s².
力是作用在物体上的推或拉。力可以改变物体的形状、速度或运动方向。力的单位是牛顿(N)。记住：1牛顿大约是一个小苹果的重量——它是让1千克物体产生1 m/s²加速度所需的力。
Friction is a force that opposes motion between two surfaces in contact. It can be useful (helping tyres grip the road) or a nuisance (causing wear in engines). Friction always acts in the opposite direction to movement.
摩擦力是一种阻碍两个接触表面相对运动的力。它既可能有用（帮助轮胎抓住路面），也可能带来麻烦（引起发动机磨损）。摩擦力的方向总是与运动方向相反。
Gravity is a force of attraction between any objects that have mass. On Earth, gravity pulls everything towards the centre of the planet. It gives objects weight. Weight is different from mass: mass is the amount of matter (measured in kg), while weight is the gravitational force on that mass (measured in N). The equation is W = m × g, where g is the gravitational field strength (about 10 N/kg on Earth).
重力是任何有质量的物体之间的一种吸引力。在地球上，重力将所有物体拉向地心。它赋予物体重量。重量与质量不同：质量是物质多少（以千克计），而重量是作用在该质量上的引力（以牛顿计）。公式为W = m × g，其中g是引力场强度（地球表面约10 N/kg）。
W = m × g
Speed tells you how fast an object is moving without regard to direction. It is a scalar quantity. The formula is speed = distance ÷ time. The SI unit is m/s. Velocity is speed in a given direction; it is a vector quantity. Two cars travelling at 30 m/s, one north and one south, have the same speed but different velocities.
速率告诉你物体运动有多快，不考虑方向。它是标量。公式为速率 = 距离 ÷ 时间。国际单位是 m/s。速度是给定方向上的速率；它是矢量。两辆车都以30 m/s行驶，一辆向北一辆向南，速率相同但速度不同。
Acceleration is the rate at which velocity changes. If an object speeds up, slows down, or changes direction, it is accelerating. The formula is a = Δv ÷ t, where Δv is the change in velocity. Acceleration is measured in m/s².
加速度是速度变化的快慢程度。物体加速、减速或改变方向时，都在做加速运动。公式为a = Δv ÷ t，其中Δv是速度变化量。加速度的单位是 m/s²。
a = Δv ÷ t
Resultant force is the single force that has the same effect as all the forces acting on an object combined. If the resultant force is zero, the object stays at rest or continues at constant velocity (Newton's First Law).
合力是跟物体上所有作用力叠加效果相同的单个力。如果合力为零，物体将保持静止或匀速直线运动（牛顿第一定律）。
2. Energy | 能量
Energy is the ability to do work. It is measured in joules (J). Energy can be stored in many ways (kinetic, gravitational potential, thermal, chemical, elastic, nuclear) and cannot be created or destroyed – only transferred or transformed (conservation of 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（动能、重力势能、热能、化学能、弹性势能、核能），不能凭空产生或消失——只能转移或转化（能量守恒）。
Kinetic energy (KE) is the energy an object has because of its motion. The faster and heavier an object, the more kinetic energy it has. KE = ½ × m × v², where m is mass in kg and v is speed in m/s.
动能 (KE) 是物体因运动而具有的能量。物体越快、越重，动能越大。KE = ½ × m × v²，其中m是质量(kg)，v是速率(m/s)。
KE = ½ × m × v²
Gravitational potential energy (GPE) is energy stored in an object because of its height above the ground. Lifting an object against gravity increases its GPE. GPE = m × g × h, where h is the height in metres.
重力势能 (GPE) 是物体因离地高度而储存的能量。把物体举高会增大其重力势能。GPE = m × g × h，其中h是高度(m)。
GPE = m × g × h
Work done is the energy transferred when a force moves an object. It is calculated as work done = force × distance moved in the direction of the force. If you push a box with a force of 10 N over 2 m, you do 20 J of work. Work and energy share the same unit, the joule.
做功是力使物体移动时所转移的能量。计算公式为做功 = 力 × 沿力方向移动的距离。用10 N的力推箱子移动2 m，做功20 J。功和能量单位相同，都是焦耳。
Power is the rate of doing work or transferring energy. A powerful machine does the same work in less time. Power = work done ÷ time, measured in watts (W). 1 W = 1 J/s.
功率是做功或能量转化的快慢。一台大功率机器能在更短时间内完成同样的功。功率 = 做功 ÷ 时间，单位是瓦特(W)。1 W = 1 J/s。
Efficiency compares useful output energy to total input energy. It is given by efficiency = useful output energy ÷ total input energy (usually expressed as a percentage or decimal). No real machine is 100% efficient because of energy dissipated as heat.
效率将有用输出能量与总输入能量进行比较。效率 = 有用输出能量 ÷ 总输入能量（常用百分数或小数表示）。没有机器能达到100%效率，因为有部分能量以热的形式耗散。
3. Waves | 波
A wave is a disturbance that transfers energy from one place to another without transferring matter. In Year 9, you study transverse and longitudinal waves. Light and water waves are transverse; sound waves are longitudinal.
波是一种将能量从一个地方传递到另一个地方而不传递物质的扰动。九年级你需要学习横波和纵波。光波和水波是横波；声波是纵波。
Amplitude is the maximum displacement of a point on the wave from its rest position. It determines the loudness of sound or brightness of light. A larger amplitude means more energy is carried by the wave.
振幅是波上某点偏离平衡位置的最大位移。它决定了声音的响度或光的亮度。振幅越大，波携带的能量越多。
Wavelength (λ) is the distance between two identical points on consecutive waves, such as crest to crest or trough to trough. It is measured in metres (m).
波长 (λ) 是相邻波上两个相同点之间的距离，如波峰到波峰或波谷到波谷。单位是米(m)。
Frequency (f) is the number of complete waves passing a fixed point per second. It is measured in hertz (Hz). If 5 waves pass each second, the frequency is 5 Hz. Frequency is inversely related to wavelength: higher frequency means shorter wavelength.
频率 (f) 是每秒通过某固定点的完整波的数量，单位是赫兹(Hz)。如果每秒通过5个波，频率就是5 Hz。频率与波长成反比：频率越高，波长越短。
Wave speed is how fast the wave is travelling. The wave equation links speed, frequency and wavelength: v = f × λ. The unit is m/s. When light enters a different medium, its speed and wavelength change, causing refraction.
波速是波传播的快慢。波动方程将波速、频率和波长联系起来：v = f × λ。单位是 m/s。当光进入不同介质时，其速度和波长会改变，从而产生折射。
v = f × λ
Reflection is when a wave bounces off a surface. The angle of incidence equals the angle of reflection (measured from the normal, an imaginary line at 90° to the surface). Smooth surfaces give specular (clear) reflection; rough surfaces cause diffuse reflection.
反射是波从表面弹回的现象。入射角等于反射角（从法线量起，法线是与表面成90°的假想线）。光滑表面产生镜面（清晰）反射；粗糙表面产生漫反射。
4. Electricity | 电
Electric current is the flow of electric charge. In a metal wire, it is a flow of electrons. Current is measured in amperes (A) using an ammeter placed in series. Conventional current flows from positive to negative, but electron flow is the opposite.
电流是电荷的流动。在金属导线中，它是电子的流动。电流用安培(A)测量，电流表必须串联在电路中。规定电流方向为正到负，但电子实际流动方向相反。
Voltage (potential difference) is the energy transferred per unit charge. It pushes the current around the circuit. Measured in volts (V) using a voltmeter connected in parallel across a component. Think of voltage as the 'electrical pressure'.
电压（电势差）是单位电荷转移的能量。它推动电流在电路中流动。电压用伏特(V)测量，电压表必须并联在元件两端。可以把电压想象成"电的压力"。
Resistance is a measure of how much a component opposes the flow of current. It is measured in ohms (Ω). A longer or thinner wire has higher resistance. Ohm's Law states that for a metal at constant temperature, V = I × R.
电阻是衡量元件对电流阻碍作用大小的量，单位是欧姆(Ω)。导线越长越细，电阻越大。欧姆定律指出，在温度不变时，金属导体的V = I × R。
V = I × R
Series circuit: components are connected end to end in a single loop. Current is the same everywhere. The total resistance adds up. If one bulb breaks, the circuit is broken and all bulbs go out.
串联电路：元件首尾相连组成单一回路。电流处处相等，总电阻等于各电阻之和。如果一个灯泡坏了，电路断开，所有灯泡熄灭。
Parallel circuit: components are connected on separate branches. Voltage across each branch is the same as the supply voltage. Total current is the sum of branch currents. If one bulb fails, others stay lit – this is why household circuits are parallel.
并联电路：元件连接在不同的支路上。各支路两端电压都等于电源电压。总电流等于各支路电流之和。如果一个灯泡损坏，其他灯泡仍发光——这就是家庭电路采用并联的原因。
5. Particle Model of Matter | 物质粒子模型
The particle model explains the properties of solids, liquids and gases by imagining tiny particles that are always moving. In solids, particles vibrate in fixed positions; in liquids, they can slide past each other; in gases, they move freely and rapidly.
粒子模型通过想象物质由不断运动的微小粒子构成，来解释固体、液体和气体的性质。固体中，粒子在固定位置振动；液体中，粒子能相互滑动；气体中，粒子自由快速运动。
Melting is the change from solid to liquid at the melting point. Boiling (or evaporation) is liquid to gas. Condensing is gas to liquid. Freezing is liquid to solid. During a change of state, the temperature remains constant while energy is absorbed or released as latent heat.
熔化是固体在熔点时变成液体。沸腾（或蒸发）是液体变气体。冷凝是气体变液体。凝固是液体变固体。在物态变化过程中，温度保持不变，而能量以潜热的形式被吸收或释放。
Density tells you how much mass is packed into a given volume. Density = mass ÷ volume, usually expressed in kg/m³ or g/cm³. A brick is denser than a sponge. The particle model explains density: particles closer together give higher density.
密度表示单位体积内所含质量多少。密度 = 质量 ÷ 体积，常用单位 kg/m³ 或 g/cm³。砖块比海绵更密实。粒子模型可以解释密度：粒子排列越紧密，密度越大。
ρ = m ÷ V
Internal energy is the total kinetic and potential energy of all the particles in a substance. Heating increases internal energy, either raising temperature or causing a change of state. The motion of particles links directly to thermal energy.
内能是物质中所有粒子的动能和势能总和。加热会增加内能，可能使温度升高或引起物态变化。粒子的运动直接与热能相关。
Gas pressure is caused by gas particles colliding with the walls of their container. More frequent or harder collisions increase pressure. Heating a sealed container raises pressure; increasing volume decreases pressure (Boyle's Law idea).
气体压强是由气体粒子撞击容器壁产生的。碰撞越频繁或越剧烈，压强越大。加热密封容器会增大压强；增大体积会降低压强（波义耳定律思想）。
6. Magnetism and Electromagnetism | 磁与电磁
Magnets have two poles: north (N) and south (S). Like poles repel; unlike poles attract. A magnetic field is the region around a magnet where magnetic forces can be felt. Field lines run from north to south and show the direction a north pole would move.
磁铁有两个磁极：北极(N)和南极(S)。同名磁极排斥，异名磁极吸引。磁场是磁铁周围能感受到磁力的区域。磁感线从北极指向南极，显示的是北极在磁场中的受力方向。
Induced magnetism occurs when a magnetic material (like iron) becomes a temporary magnet when placed inside a magnetic field. Remove the field, and it loses most of its magnetism. This is different from permanent magnets, like steel, which retain their magnetism.
感应磁性是当铁等磁性材料放入磁场中时会变成临时磁体的现象。撤去磁场，它会失去大部分磁性。这与永久磁铁（如钢）不同，后者能保持磁性。
Electromagnet: a coil of wire (solenoid) with a current passing through it creates a magnetic field. Adding an iron core increases the strength greatly. Electromagnets are very useful because they can be switched on and off, and their strength can be varied by changing the current or the number of coils. Used in electric bells, relays and lifting scrap metal.
电磁铁：有电流通过的线圈（螺线管）会产生磁场。加入铁芯能大大增强磁场。电磁铁非常有用，因为它可以通断控制，并且可通过改变电流大小或线圈匝数来调节磁性强弱。用于电铃、继电器和吸吊废金属。
The motor effect occurs when a current-carrying wire is placed in a magnetic field, experiencing a force. This is the principle behind electric motors. The force is strongest when the wire is perpendicular to the field. Fleming's left-hand rule helps predict the direction of motion.
电动机效应是载流导线置于磁场中会受到力的作用。这就是电动机的基本原理。当导线与磁场垂直时作用力最大。弗莱明左手定则可以帮助预测运动方向。
7. Space Physics | 太空物理
Our Solar System consists of the Sun, eight planets, moons, dwarf planets, asteroids and comets. The planets orbit the Sun because of the Sun's enormous gravitational pull. Gravity provides the centripetal force needed for nearly circular orbits.
我们的太阳系由太阳、八大行星、卫星、矮行星、小行星和彗星组成。行星因太阳巨大的引力而绕其运行。引力提供了近圆形轨道所需的向心力。
Orbit is the curved path of a celestial object around a star, planet or moon. The closer a planet is to the Sun, the faster it must move to stay in orbit and the shorter its year. This is because gravity is stronger at shorter distances.
轨道是天体围绕恒星、行星或卫星运行的曲线路径。行星离太阳越近，必须移动越快才能保持在轨，其公转周期（年）也越短。因为距离近时引力更强。
Seasons on Earth are caused by the 23.5° tilt of its axis, not by varying distance from the Sun. When the Northern Hemisphere is tilted towards the Sun, it experiences summer; when tilted away, winter. The opposite happens south of the equator.
地球上的季节是由地轴倾斜23.5°造成的，而不是由与太阳距离的变化引起的。北半球偏向太阳时是夏季，偏离时是冬季。赤道以南则相反。
A light-year is a unit of distance, not time. It is the distance light travels in one year, about 9.5 trillion kilometres. Astronomers use light-years to express vast distances between stars and galaxies.
光年是距离单位，而不是时间单位。它是光在一年中传播的距离，约9.5万亿公里。天文学家用光年来表示恒星和星系间的遥远距离。
8. Key Quantities and Units | 关键量与单位
Memorising the standard units and their symbols will help you plug numbers into equations correctly. The table below summarises the most common physical quantities you will meet in Year 9 WJEC Physics.
记住标准单位及其符号能帮助你正确地将数据代入公式。下表总结了九年级 WJEC 物理中最常见的物理量。
| Quantity (English) | 中文 | Symbol | Unit | Unit Symbol |
|---|---|---|---|---|
| Distance / Displacement | 距离 / 位移 | d, s | met
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