📚 KS3 OCR Physics: Key Concepts Review | KS3 OCR 物理：核心知识点梳理
Welcome to your essential guide to KS3 OCR Physics. This article covers the core topics you will encounter in years 7, 8 and 9, from energy and forces to waves, electricity and beyond. Each concept is explained clearly so you can build a solid foundation before moving on to GCSE. Read through the English explanations and their matching Chinese versions to strengthen your understanding in both languages.
欢迎来到 KS3 OCR 物理的核心指南。本文将涵盖七、八、九年级遇到的关键主题，从能量、力到波、电学以及更广阔的宇宙。每个概念都清晰解释，帮助你在进入 GCSE 之前打下坚实的基础。通过阅读英文解释和对应的中文版本，你可以用两种语言加深理解。
1. Energy and Energy Transfer | 能量与能量转移
Energy is the ability to do work and it exists in many forms. Common types include kinetic energy (movement), gravitational potential energy (height), elastic potential energy (stretched or compressed materials), thermal energy (heat), chemical energy (food and fuels), electrical energy, nuclear energy, light energy and sound energy. The unit of energy is the joule (J).
能量是做功的能力，并且以多种形式存在。常见的类型包括动能（运动）、重力势能（高度）、弹性势能（拉伸或压缩的材料）、热能（热量）、化学能（食物和燃料）、电能、核能、光能和声能。能量的单位是焦耳 (J)。
Energy cannot be created or destroyed, only transferred, stored or dissipated. This is the law of conservation of energy. Energy transfers happen in different ways: by heating (from hot to cold), by doing work (a force moving an object) and by travelling as waves (sound or light). A Sankey diagram shows how much useful energy is transferred and how much is wasted.
能量不能凭空产生或消失，只能转移、储存或耗散。这就是能量守恒定律。能量转移以不同方式发生：通过加热（从高温到低温）、通过做功（力使物体移动）以及通过波传播（声音或光）。桑基图显示有多少有用的能量被转移，以及有多少被浪费。
Heat transfer occurs through three processes. Conduction takes place mainly in solids as vibrating particles pass energy to neighbours. Convection happens in fluids (liquids and gases) when warmer, less dense regions rise and cooler, denser regions sink, creating a convection current. Radiation is the transfer of thermal energy by infrared waves and does not require particles – it can travel through a vacuum.
热传递通过三个过程发生。传导主要在固体中进行，振动粒子将能量传递给相邻粒子。对流发生在流体（液体和气体）中，较热、密度较小的区域上升，较冷、密度较大的区域下沉，形成对流循环。辐射是通过红外波传递热能，不需要介质——它可以穿过真空。
2. Forces and Motion | 力与运动
A force is a push or a pull that can change an object’s shape, speed or direction. Contact forces include friction, air resistance, tension and normal reaction. Non-contact forces include gravitational force, magnetism and electrostatic force. The unit of force is the newton (N).
力是推或拉，可以改变物体的形状、速度或方向。接触力包括摩擦力、空气阻力、张力和法向反作用力。非接触力包括重力、磁力和静电力。力的单位是牛顿 (N)。
If several forces act on an object, we add them as vectors to find the resultant force. When the resultant force is zero, the object remains stationary or moves at a constant speed in a straight line. When there is a net force, the object accelerates, decelerates or changes direction. Weight is the force due to gravity: W = m g, where m is mass (kg) and g is the gravitational field strength (≈ 10 N/kg on Earth).
如果有多个力作用在一个物体上，我们将它们作为矢量相加得到合力。当合力为零时，物体保持静止或沿直线匀速运动。当存在净力时，物体会加速、减速或改变方向。重量是由重力引起的力：W = m g，其中 m 是质量（kg），g 是引力场强度（地球上约为 10 N/kg）。
speed = distance ÷ time or v = d / t
速度 = 距离 ÷ 时间 或 v = d / t
Speed tells us how fast something is moving. A distance–time graph shows motion: a horizontal line means stationary, a straight sloping line means constant speed, and a steeper line means a higher speed. Curves on the graph indicate acceleration or deceleration.
速度告诉我们物体运动的快慢。距离-时间图显示运动：水平线表示静止，斜直线表示匀速，线越陡速度越大。图像上的曲线表示加速或减速。
3. Pressure | 压强
Pressure is a measure of how concentrated a force is over an area. It is calculated as force per unit area. The formula is:
压强用来衡量力在面积上的集中程度。它的计算是单位面积上所受的力。公式为：
p = F ÷ A
The unit of pressure is the pascal (Pa), where 1 Pa = 1 N/m². To increase pressure you can either increase the force or decrease the area – this is why knives are sharp. To decrease pressure you can increase the area, for example using snowshoes or wide tyres.
压强的单位是帕斯卡 (Pa)，1 Pa = 1 N/m²。要增大压强，可以增大力量或减小面积——这就是为什么刀很锋利。要减小压强，可以增大面积，例如使用雪鞋或宽轮胎。
In liquids, pressure increases with depth because of the weight of the liquid above. The pressure at a given depth is given by p = h ρ g, where h is depth, ρ is density and g is gravitational field strength. In gases, pressure is caused by constantly moving particles colliding with the walls of the container. Increasing the temperature makes particles move faster, increasing pressure if the volume is fixed.
在液体中，压强随深度增加而增大，因为上方液体的重量。给定深度的压强由 p = h ρ g 给出，其中 h 是深度，ρ 是密度，g 是引力场强度。在气体中，压强是由不断运动的粒子撞击容器壁所引起的。升高温度使粒子运动更快，在体积不变时增大压强。
4. Waves – Sound | 波——声音
Sound is caused by vibrating objects and travels as a longitudinal wave. It needs a medium (solid, liquid or gas) to travel through; it cannot travel through a vacuum. Sound travels fastest in solids and slowest in gases. In air, the speed of sound is roughly 340 m/s.
声音由物体振动产生，以纵波形式传播。它需要介质（固体、液体或气体）来传播；不能穿过真空。声音在固体中传播最快，在气体中最慢。在空气中，声速大约为 340 m/s。
The features of a sound wave are its frequency (the number of vibrations per second, measured in hertz, Hz) and amplitude (the maximum displacement from rest). A higher frequency gives a higher pitch, and a larger amplitude gives a louder sound. Humans can typically hear frequencies from about 20 Hz to 20 000 Hz. Sounds above 20 000 Hz are called ultrasound and are used for sonar and medical imaging.
声波的特征包括频率（每秒振动的次数，以赫兹 Hz 为单位）和振幅（离开平衡位置的最大位移）。频率越高，音调越高；振幅越大，声音越响。人类通常能听到大约 20 Hz 到 20 000 Hz 的频率。高于 20 000 Hz 的声音称为超声波，用于声呐和医学成像。
wave speed = frequency × wavelength or v = f λ
波速 = 频率 × 波长 或 v = f λ
Echoes are reflections of sound. Soft materials absorb sound and are used for soundproofing. Oscilloscope traces help us visualise sound waves and compare pitch and loudness.
回声是声音的反射。柔软的材料吸收声音，用于隔音。示波器的波形帮助我们直观地看到声波，并比较音调和响度。
5. Waves – Light | 波——光
Light is a transverse wave that does not require a medium and travels at a speed of about 3 × 10⁸ m/s in a vacuum. Light travels in straight lines, which explains the formation of shadows and eclipses.
光是横波，无需介质，在真空中速度约为 3 × 10⁸ m/s。光沿直线传播，这解释了阴影和日食、月食的形成。
The law of reflection states that the angle of incidence equals the angle of reflection. Refraction occurs when light passes from one medium to another and changes speed, causing it to change direction. A prism can disperse white light into the visible spectrum: red, orange, yellow, green, blue, indigo and violet.
反射定律指出入射角等于反射角。当光从一种介质进入另一种介质时，速度改变，方向发生偏折，这叫做折射。棱镜可以将白光色散成可见光谱：红、橙、黄、绿、蓝、靛、紫。
The colour of an object depends on which wavelengths of light it reflects or transmits. A red apple reflects red light and absorbs the other colours. The primary colours of light are red, green and blue; combining them gives white light. Coloured filters work by transmitting only certain colours.
物体的颜色取决于它反射或透射的光的波长。红色苹果反射红光，吸收其他颜色。光的三原色是红、绿、蓝；将它们混合得到白光。彩色滤光片只透过特定颜色的光。
6. Electricity | 电学基础
An electric current is a flow of electric charge, usually carried by electrons in a wire. Current is measured in amperes (A). Voltage (potential difference) provides the push that drives the current around a circuit and is measured in volts (V). Resistance opposes the flow of current and is measured in ohms (Ω).
电流是电荷的流动，通常由导线中的电子携带。电流以安培 (A) 为单位。电压（电势差）提供推动电流在电路中流动的动力，以伏特 (V) 为单位。电阻阻碍电流流动，以欧姆 (Ω) 为单位。
V = I R
In a series circuit, the current is the same at all points, the supply voltage is shared between components, and the total resistance is the sum of the individual resistances: Rₜ = R₁ + R₂ + …. In a parallel circuit, the voltage across each branch is the same as the supply, while the currents in the branches add up to give the total current.
在串联电路中，各处电流相等，电源电压在各元件之间分配，总电阻等于各电阻之和：Rₜ = R₁ + R₂ + …。在并联电路中，每条支路两端的电压与电源电压相同，各支路电流之和等于总电流。
Common circuit symbols include a cell, battery, lamp, switch, resistor, ammeter and voltmeter. For safety, circuits use fuses that melt if the current is too high, breaking the circuit. Never handle electrical equipment with wet hands and always check for damaged wires.
常见电路元件符号包括电池、电池组、灯泡、开关、电阻器、电流表和电压表。出于安全，电路使用保险丝，当电流过大时熔断，断开电路。切勿用湿手触摸电器，并始终检查破损的电线。
7. Magnetism | 磁学
A magnet has a north pole and a south pole. Like poles repel each other; unlike poles attract. Magnetic materials include iron, nickel and cobalt. The region around a magnet where it can exert a force is its magnetic field, shown by field lines that run from north to south.
磁铁有北极和南极。同极相斥，异极相吸。磁性材料包括铁、镍和钴。磁铁周围能产生力的区域叫做磁场，由从北极指向南极的磁感线表示。
The Earth itself has a magnetic field, which is why a compass needle points roughly north. When an electric current flows through a wire, it creates a magnetic field around it. An electromagnet is made by wrapping wire into a coil around a soft iron core. Its strength can be increased by adding more turns of the coil, increasing the current or inserting the iron core.
地球本身有一个磁场，这就是为什么指南针大致指向北方。当电流通过导线时，周围会产生磁场。电磁铁是用导线绕制线圈并插入软铁芯制成的。增加线圈匝数、增大电流或插入铁芯都可以增强电磁铁的磁性。
Electromagnets are used in electric bells, relays and lifting scrap metal. Unlike permanent magnets, they can be switched on and off.
电磁铁用于电铃、继电器和吊运废金属。与永磁体不同，电磁铁可以随时通断。
8. States of Matter and Particle Model | 物态与粒子模型
All substances are made of tiny particles that are constantly moving. In solids, particles are arranged in a regular pattern, vibrate in fixed positions and have the least energy. In liquids, particles are loosely arranged, can slide past one another and take the shape of their container. In gases, particles are far apart, move quickly in random directions and have the most energy.
所有物质都由不断运动的微小粒子组成。固态时，粒子有规律地排列，在固定位置振动，能量最低。液态时，粒子排列松散，可以相互滑动，呈现容器的形状。气态时，粒子相距很远，快速向各个方向随机运动，能量最高。
density = mass ÷ volume or ρ = m ÷ V
密度 = 质量 ÷ 体积 或 ρ = m ÷ V
Changes of state include melting (solid to liquid), freezing (liquid to solid), boiling and evaporating (liquid to gas), condensation (gas to liquid), sublimation (solid to gas) and deposition (gas to solid). During a change of state, the temperature remains constant while the particles reorganise.
物态变化包括熔化（固体→液体）、凝固（液体→固体）、沸腾与蒸发（液体→气体）、凝结（气体→液体）、升华（固体→气体）和凝华（气体→固体）。在物态变化过程中，温度保持不变，而粒子重新排列。
Diffusion is the random movement of particles from an area of high concentration to a low concentration, happening fastest in gases. Gas pressure increases if volume decreases (more frequent collisions) or if temperature increases (particles move faster).
扩散是粒子从高浓度区域向低浓度区域的随机运动，在气体中最快。体积减小（碰撞更频繁）或温度升高（粒子运动更快）都会使气体压强增大。
9. Space and the Universe | 宇宙与空间
Our Solar System consists of the Sun – an average-sized star – and eight planets that orbit it because of gravity. In order from the Sun, the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The asteroid belt lies between Mars and Jupiter. Moons orbit planets, and artificial satellites orbit Earth for communication and research.
我们的太阳系由太阳（一颗中等大小的恒星）以及由于引力而绕其运行的八大行星组成。按距太阳由近到远排列：水星、金星、地球、火星、木星、土星、天王星和海王星。小行星带位于火星与木星之间。卫星围绕行星运行，人造卫星绕地球运行用于通信和研究。
The Earth’s rotation on its axis causes day and night, taking 24 hours. Its orbit around the Sun takes one year (3651⁄4 days), and the tilt of the Earth’s axis gives us seasons. A light-year is the distance light travels in one year, used to measure vast distances in space.
地球绕地轴自转 24 小时形成昼夜。地球绕太阳公转一周为一年（3651⁄4 天），地轴的倾斜给我们带来四季。光年是光在一年内传播的距离，用于测量宇宙中广阔的尺度。
Phases of the Moon occur as it orbits Earth, changing the portion of the illuminated half we can see. Solar eclipses happen when the Moon passes between the Sun and the Earth, and lunar eclipses when the Earth is between the Sun and the Moon.
月相是月球绕地球运行过程中，我们看到的被照亮部分不断变化的形状。当月球经过太阳和地球之间时发生日食，当地球在太阳和月球之间时发生月食。
10. Energy Resources and Electricity Generation | 能源与发电
Energy resources used to generate electricity are divided into non-renewable and renewable. Non-renewable resources include fossil fuels (coal, oil, natural gas) and nuclear fuel (uranium). They are finite and release greenhouse gases when burned (except nuclear, which produces radioactive waste). Renewable resources include solar, wind, wave, tidal, hydroelectric, geothermal and biomass. They are replenished naturally and generally have less environmental impact.
用于发电的能源分为不可再生能源与可再生能源。不可再生能源包括化石燃料（煤、石油、天然气）和核燃料（铀）。它们是有限的，燃烧时释放温室气体（核能除外，但会产生放射性废物）。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。它们可以自然补充，通常对环境影响较小。
In a typical thermal power station, a fuel is burned to heat water and produce steam. The high-pressure steam drives a turbine, which turns a generator that produces electricity. In renewable systems like wind turbines, the wind directly turns the blades, and wave or tidal generators use moving water to spin turbines.
在典型的热电站中，燃料燃烧将水加热产生蒸汽。高压蒸汽驱动汽轮机，带动发电机旋转产生电力。在风力涡轮机等可再生能源系统中，风直接转动叶片，波浪或潮汐发电机则利用运动的水来推动涡轮。
It is important to use energy efficiently and reduce waste. Energy saving reduces the demand for fossil fuels and lowers carbon dioxide emissions, helping to combat climate change.
高效利用能源和减少浪费非常重要。节能降低了对化石燃料的需求，减少了二氧化碳排放，有助于应对气候变化。
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