📚 GCSE WJEC Physics: End-of-Term Revision Outline | GCSE WJEC 物理：期末复习提纲
Preparing for the WJEC GCSE Physics examination requires a structured approach that consolidates all three units: Electricity, Energy and Waves (Unit 1), Forces, Space and Radioactivity (Unit 2), and Practical Assessment (Unit 3). This revision outline distils the essential topics, key equations, and common pitfalls into a clear, bilingual guide. By working through each section systematically, you can strengthen your conceptual understanding, master the required calculations, and build confidence for both the theory papers and the practical-based questions. Remember that the WJEC specification rewards precise scientific vocabulary and the ability to apply knowledge to unfamiliar contexts – so as you revise, focus on explaining concepts in your own words, practising past-paper questions, and linking different areas of the syllabus together.
备考 WJEC GCSE 物理需要系统梳理全部三个单元：Unit 1 电学、能量与波动，Unit 2 力、空间与放射性，以及 Unit 3 实验评估。这份双语复习提纲把核心知识点、关键公式和常见易错点浓缩整理，方便你按主题逐一巩固。通过每节的梳理，你可以加深对概念的理解，掌握必要的计算，并为理论卷和实验相关题目树立信心。WJEC 考纲重视准确的科学术语和将知识应用于新情境的能力，因此复习时要注重用自己的语言解释概念，多练历年真题，并尝试把不同板块的内容联系起来。
1. Energy Stores and Systems | 能量储存与系统
Energy is never destroyed; it is transferred between stores. The main energy stores include kinetic, gravitational potential, elastic potential, thermal (internal), chemical, nuclear, and magnetic. When a system changes – for example a ball rolling downhill – energy is transferred mechanically from the gravitational potential store to the kinetic store. Other transfer pathways are electrical work, heating, and radiation. The principle of conservation of energy states that the total energy of a closed system remains constant. This allows us to use equations such as GPE = mgh and KE = ½mv² to quantify how much energy moves from one store to another, assuming no energy is lost to the surroundings.
能量不会凭空消失，而是在不同储存方式之间转移。主要的能量储存包括动能、重力势能、弹性势能、热（内）能、化学能、核能和磁能。当系统发生变化时——比如球从斜坡滚下——能量通过机械做功从重力势能储存转移到动能储存。其他转移途径还有电做功、加热和辐射。能量守恒定律指出，封闭系统的总能量保持不变。利用 GPE = mgh 和 KE = ½mv² 等方程，我们可以定量计算出有多少能量从一种储存转移到另一种，前提是假设没有能量散失到周围环境中。
Efficiency is a vital concept: it tells you how much of the total input energy is transferred usefully. Efficiency = useful output energy transfer ÷ total input energy transfer (often expressed as a percentage). In real systems, some energy is always dissipated – typically as thermal energy to the surroundings. Understanding energy transfers also involves power, the rate of energy transfer: P = E ÷ t, measured in watts (W). A 60 W light bulb transfers 60 J of electrical energy every second, but only a small fraction is converted to useful light; the rest heats up the bulb and the air.
效率是一个重要概念：它告诉你总输入能量中有多少被有用转移。效率 = 有用输出能量 ÷ 总输入能量（常用百分数表示）。实际系统中总会有能量耗散——通常是以热能形式散失到周围环境。理解能量转移还要掌握功率，即能量转移的速率：P = E ÷ t，单位是瓦特（W）。一只 60 W 灯泡每秒钟转移 60 J 的电能，但只有一小部分转变成有用的光，其余能量使灯泡和周围空气升温。
2. Particle Model and Density | 粒子模型与密度
Matter is made of tiny particles that are in constant, random motion. The particle model explains the differences between solids, liquids and gases: in solids, particles vibrate in fixed positions; in liquids, they move past each other; in gases, they move freely at high speeds. Heating increases the internal energy of a substance, raising its temperature (or causing a change of state if enough energy is supplied). Density ρ = mass ÷ volume (kg/m³) is a characteristic property of materials. The arrangement and motion of particles directly affect density – gases are much less dense than liquids and solids because their particles are widely spaced.
物质由不断做无规则运动的微小粒子组成。粒子模型可以解释固体、液体和气体的差异：固体中的粒子在固定位置振动；液体中的粒子可以相互滑动；气体中的粒子则自由高速运动。加热会增加物质的内能，使其温度升高（如果供给足够能量，还会引起状态变化）。密度 ρ = 质量 ÷ 体积（单位 kg/m³）是材料的一种特征性质。粒子的排列和运动方式直接影响密度——气体密度远小于液体和固体，就是因为粒子间距离很大。
Changes of state require energy without a change in temperature: specific latent heat L = E ÷ m (J/kg). For melting or boiling, energy is used to break bonds between particles rather than raise kinetic energy. The specific heat capacity c describes the energy needed to raise 1 kg of a substance by 1 °C: ΔE = mcΔθ. These calculations appear frequently in WJEC questions, often combined with power or efficiency contexts. Make sure you can interpret heating graphs and explain the horizontal sections in terms of latent heat.
状态变化需要能量但温度不变：比潜热 L = E ÷ m（单位 J/kg）。在熔化或沸腾过程中，能量用于打破粒子间的结合而非提高动能。比热容 c 表示使 1 kg 物质升温 1 °C 所需的能量：ΔE = mcΔθ。这些计算常出现在 WJEC 试题中，并往往结合功率或效率问题。务必学会解读加热曲线，能用潜热概念解释水平线段。
3. Electric Circuits and Current | 电路与电流
Electric current is the rate of flow of charge. In a metallic conductor, current consists of free electrons drifting under a potential difference. Charge Q = It, measured in coulombs (C). Potential difference (voltage) is the energy transferred per coulomb of charge: V = E ÷ Q. Resistance opposes current; Ohm’s law states that V = IR for a resistor at constant temperature. Components such as diodes and filament lamps have non-ohmic behaviour: their resistance changes with current or temperature. Circuit symbols and diagrams are essential for interpreting and designing circuits.
电流是电荷的流动速率。在金属导体中，电流是自由电子在电势差作用下漂移形成的。电荷量 Q = It，单位是库仑（C）。电势差（电压）是每库仑电荷转移的能量：V = E ÷ Q。电阻阻碍电流；欧姆定律指出，在恒温条件下，对于电阻器有 V = IR。二极管和灯丝等元件则表现出非欧姆特性：它们的电阻随电流或温度而变化。电路符号和电路图对于解读和设计电路至关重要。
Series and parallel circuits have distinct rules. In series, current is the same everywhere, total resistance R_total = R₁ + R₂ + … , and the supply voltage is shared across components. In parallel, the voltage across each branch is the same as the supply, total current is the sum of branch currents, and the total resistance decreases as more branches are added. Understanding these rules allows you to predict how adding or removing components affects brightness of lamps or ammeter readings. WJEC questions often combine series and parallel sections, so practise simplifying networks step by step.
串联和并联电路各有不同的规则。串联电路中各处电流相等，总电阻 Rₜₒₜₐₗ = R₁ + R₂ + … ，电源电压在元件间分配。并联电路中各支路电压等于电源电压，总电流等于各支路电流之和，而总电阻随支路增加而减小。理解这些规则就能预测增加或移除元件对灯泡亮度或电流表读数的影响。WJEC 试题常把串联和并联部分组合在一起，所以要练习逐步简化电路网络。
4. Mains Electricity and Power | 市电与电力
UK mains electricity is an alternating current (a.c.) with a frequency of 50 Hz and a voltage of approximately 230 V. The live wire carries the alternating potential, the neutral wire completes the circuit, and the earth wire is a safety path to ground. Plugs and sockets use colour-coded insulation: brown for live, blue for neutral, and green/yellow for earth. Fuses and circuit breakers are protective devices: a fuse melts if too much current flows, breaking the circuit; a residual current circuit breaker (RCCB) detects a difference between live and neutral currents and disconnects even faster.
英国家用市电是频率 50 Hz、电压约 230 V 的交流电（a.c.）。火线承载交变电势，零线构成回路，地线是通向大地的安全通道。插头和插座采用彩色绝缘层：棕色为火线，蓝色为零线，绿/黄色为地线。保险丝和断路器是保护装置：电流过大时保险丝熔断，切断电路；漏电断路器（RCCB）则检测火线与零线电流的差异，并以更快的速度断开电路。
Power in electrical circuits can be calculated using P = IV, P = I²R, or P = V²/R. Energy transferred E = Pt, commonly expressed in kilowatt-hours (kWh) for domestic usage. A typical WJEC calculation asks students to find the cost of running an appliance: cost = power (kW) × time (h) × price per kWh. Safety considerations – double insulation, no earth wire needed for plastic-cased appliances, and the importance of not overloading sockets – are regularly assessed.
电路功率可用 P = IV、P = I²R 或 P = V²/R 计算。传递的能量 E = Pt，家庭用电常以千瓦时（kWh）为单位。典型的 WJEC 计算题会要求计算电器的运行费用：费用 = 功率（kW）× 时间（h）× 每千瓦时电价。安全方面的考点——双重绝缘、塑料外壳电器无需地线、避免插座过载的重要性——经常出现在考题中。
5. Atomic Structure and Nuclear Radiation | 原子结构与核辐射
Atoms consist of a tiny nucleus containing protons and neutrons, surrounded by electrons in shells. An atom’s atomic (proton) number defines the element; its mass number is the total of protons and neutrons. Isotopes are atoms of the same element with different numbers of neutrons. Some isotopes are unstable and emit nuclear radiation to become more stable. The three main types of radiation are alpha (α), beta (β), and gamma (γ). Alpha particles are helium nuclei (²⁴He), strongly ionising but least penetrating. Beta particles are fast electrons, moderately ionising and penetrating. Gamma rays are electromagnetic waves, weakly ionising but highly penetrating.
原子由包含质子和中子的微小原子核以及核外分层排布的电子组成。原子的原子序数（质子数）决定了元素种类；质量数是质子数和中子数之和。同位素是同种元素中中子数不同的原子。一些同位素不稳定，会释放核辐射以趋向稳定。三种主要辐射类型是 α、β 和 γ。α 粒子是氦核（²⁴He），电离作用最强但贯穿能力最弱。β 粒子是高速电子，电离和贯穿能力居中。γ 射线是电磁波，电离作用最弱但贯穿能力极强。
Radioactivity is a random process; the half-life is the time taken for half the unstable nuclei in a sample to decay, or for the count rate to halve. Half-life can be found from decay graphs. Nuclear equations balance mass numbers and atomic numbers: for example, ²³⁸U → ²³⁴Th + ²⁴He for alpha decay. Background radiation from rocks, cosmic rays, and human activities must be subtracted when measuring a source. Applications include smoke detectors (alpha), thickness monitoring (beta), and sterilisation or cancer treatment (gamma). Safety precautions include using tongs, keeping sources in lead-lined containers, and minimising exposure time.
放射性是一个随机过程；半衰期是指样品中一半的不稳定核发生衰变所需的时间，或者计数率减半的时间。半衰期可依据衰变曲线求得。核方程要求质量数和原子序数守恒，例如 α 衰变：²³⁸U → ²³⁴Th + ²⁴He。测量放射源时必须扣除来自岩石、宇宙射线和人类活动的本底辐射。应用包括烟雾探测器（α）、厚度监控（β）以及灭菌或癌症治疗（γ）。安全预防措施包括使用镊子、将放射源储存在铅衬容器中，并尽量减少接触时间。
6. Motion and Forces | 运动与力
Speed is a scalar quantity; velocity is a vector – it has direction. The average speed v = d ÷ t. On a distance-time graph, the gradient gives speed. Acceleration is the rate of change of velocity: a = (v – u) ÷ t. Velocity-time graphs provide even more information: the gradient gives acceleration, the area under the graph gives displacement. Constant velocity appears as a horizontal line, constant acceleration as a straight sloping line. Free fall near Earth’s surface has a uniform acceleration g ≈ 9.8 m/s².
速率是标量，速度是矢量——既有大小也有方向。平均速率 v = d ÷ t。在距离-时间图上，斜率表示速率。加速度是速度的变化率：a = (v – u) ÷ t。速度-时间图提供更多信息：斜率表示加速度，图线下的面积表示位移。匀速运动表现为水平线段，匀加速运动表现为倾斜的直线。靠近地球表面的自由落体具有恒定加速度 g ≈ 9.8 m/s²。
Forces are pushes or pulls, measured in newtons (N). They can be contact forces (friction, tension, normal contact) or non-contact forces (gravity, magnetism, electrostatic). Newton’s First Law states that an object remains at rest or in uniform motion unless acted on by a resultant force. Resultant force is found by combining all forces along the same line; if resultant force is zero, the object is either stationary or moving at constant velocity. Resolving forces into perpendicular components is a key skill for inclined plane problems.
力是推或拉的作用，单位是牛顿（N）。力可分为接触力（摩擦力、张力、法向接触力）和非接触力（引力、磁力、静电力）。牛顿第一定律指出，除非受到合力作用，物体将保持静止或匀速直线运动。合力可由沿同一直线的各个力求矢量和得出；合力为零则物体要么静止要么匀速运动。将力分解成垂直分量是处理斜面问题的一项关键技能。
7. Newton’s Second Law and Momentum | 牛顿第二定律与动量
Newton’s Second Law links resultant force, mass and acceleration: F = ma. This tells you that for a given force, a larger mass experiences a smaller acceleration. The inertial mass of an object measures how difficult it is to change its velocity. Weight W = mg is the force of gravity on a mass; weight is not the same as mass. In free-body diagrams, always label forces clearly and ensure they are drawn from the centre of mass if treating the object as a particle.
牛顿第二定律将合力、质量和加速度联系起来：F = ma。它表明，对于给定大小的力，质量越大的物体加速度越小。物体的惯性质量衡量的是改变其速度的难易程度。重量 W = mg 是物体所受的重力；重量与质量不是同一个概念。在受力分析图中，务必要清楚地标示各个力，若将物体视为质点，就从质心出发展示力的作用点。
Momentum p = mv (kg m/s) is a vector quantity. In a closed system, total momentum before an event equals total momentum afterwards – the principle of conservation of momentum. This is used to analyse collisions and explosions. Force is also the rate of change of momentum: F = (mv – mu) ÷ t. Car safety features such as crumple zones, seat belts and airbags increase the time over which a collision force acts, thereby reducing the force on the occupants. You should be able to apply momentum equations to problems involving recoil and collisions, and interpret force-time graphs.
动量 p = mv（单位 kg m/s）是矢量。在封闭系统中，事件前的总动量等于事件后的总动量——这就是动量守恒定律。这用于分析碰撞和爆炸问题。力也可以表示为动量的变化率：F = (mv – mu) ÷ t。汽车安全设施如溃缩区、安全带和安全气囊延长了碰撞过程中力的作用时间，从而减小了乘客所受的力。你需要能应用动量方程求解反冲和碰撞问题，并会解读力-时间图像。
8. Wave Properties and Behaviour | 波的性质与行为
Waves transfer energy without transferring matter. In transverse waves (e.g. water ripples, electromagnetic waves), oscillations are perpendicular to the direction of energy transfer. In longitudinal waves (e.g. sound), oscillations are parallel to the direction of energy transfer. Key wave quantities: amplitude (maximum displacement from rest), wavelength λ (distance between two consecutive equivalent points), frequency f (number of waves per second, hertz), and period T = 1/f. The wave speed equation is v = fλ.
波传递能量而不传递物质。在横波（如水波、电磁波）中，振动方向与能量传递方向垂直。在纵波（如声波）中，振动方向与能量传递方向平行。波的关键物理量：振幅（离开平衡位置的最大位移）、波长 λ（相邻两个对应点之间的距离）、频率 f（每秒通过的完整波数，单位赫兹）以及周期 T = 1/f。波速方程是 v = fλ。
All waves can be reflected, refracted and diffracted. The law of reflection states that the angle of incidence equals the angle of reflection, measured from the normal. Refraction occurs when a wave changes speed as it crosses a boundary between media; if it slows down, it bends towards the normal. Diffraction is the spreading of waves as they pass through a gap or around an obstacle; the effect is most noticeable when the gap width is similar to the wavelength. Sound waves provide familiar examples of diffraction, while light waves require very narrow slits to show noticeable diffraction.
所有波都能发生反射、折射和衍射。反射定律指出，入射角等于反射角，两者均从法线量起。折射发生在波越过介质边界速度改变时；如果波速变慢，波会向法线偏折。衍射是波通过狭缝或绕过障碍物时扩展传播的现象；当缝宽与波长相近时，衍射效应最为明显。声波常常展现明显的衍射现象，而光波需要极窄的缝才能观察到显著的衍射。
9. The Electromagnetic Spectrum | 电磁波谱
Electromagnetic (EM) waves are transverse waves that travel at 3 × 10⁸ m/s in a vacuum. The spectrum, in order of increasing frequency and decreasing wavelength, runs: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays. All EM waves can be reflected and refracted, and they transfer energy from a source to an absorber. The higher the frequency, the more energy each photon carries – this explains why ultraviolet, X-rays and gamma rays are ionising and potentially harmful to living tissue.
电磁波是横波，在真空中以 3 × 10⁸ m/s 的速度传播。电磁波谱按频率递增、波长递减的顺序排列为：无线电波、微波、红外线、可见光、紫外线、X 射线和伽马射线。所有电磁波都能发生反射和折射，并将能量从源传递到吸收体。频率越高，每个光子携带的能量越多——这就解释了为什么紫外线、X 射线和伽马射线具有电离作用，可能对活体组织造成伤害。
Each region of the EM spectrum has characteristic uses and hazards. Radio waves are used for communication, microwaves for cooking and satellite transmissions, infrared for thermal imaging and remote controls, visible light for seeing, ultraviolet for sun tanning and security marking, X-rays for medical imaging, and gamma rays for sterilisation and cancer therapy. Hazards include internal heating from microwaves, skin burns and skin cancer from ultraviolet, and cell mutation from high-energy ionising radiation. WJEC exam questions often ask you to link a wave’s properties to its specific application.
电磁波谱的每一频段都有其典型的用途和危害。无线电波用于通信，微波用于烹饪和卫星传输，红外线用于热成像和遥控，可见光用于视觉，紫外线用于晒黑和防伪标识，X 射线用于医学成像，伽马射线用于灭菌和癌症治疗。相关危害包括微波引起体内加热、紫外线导致皮肤灼伤和皮肤癌，以及高能电离辐射引起的细胞突变。WJEC 试题常要求考生将波的特性与其具体应用联系起来。
10. Magnetism and the Motor Effect | 磁学与电动机效应
Magnets have north and south poles; like poles repel, unlike poles attract. A magnetic field is a region where a magnetic material experiences a force. Field lines point from north to south and are closest together where the field is strongest. An electric current flowing through a wire produces a magnetic field around it – this is electromagnetism. The field pattern around a straight wire forms concentric circles; reversing the current reverses the field direction. A solenoid (coil of wire) produces a uniform magnetic field inside, similar to a bar magnet, and its strength can be increased by adding an iron core, increasing the current, or increasing the number of turns.
磁铁有 N 极和 S 极；同极相斥，异极相吸。磁场是磁性材料受到力的作用的空间区域。磁感线从 N 极指向 S 极，在磁场最强的地方磁感线最密。电流通过导线时会在导线周围产生磁场——这就是电磁效应。直导线周围的磁场呈同心圆状；反向电流会使磁场方向反转。螺线管（线圈）内部产生匀强磁场，类似于条形磁铁；加入铁芯、增大电流或增加线圈匝数都可以增强磁场强度。
The motor effect occurs when a current-carrying conductor is placed in a magnetic field and experiences a force. Fleming’s left-hand rule gives the directions: thumb = motion (force), first finger = magnetic field (N to S), second finger = current. The size of the force can be increased by using a stronger magnet, a larger current, or more wire in the field. The simple electric motor uses a coil that spins between magnet poles; a split-ring commutator swaps the current direction every half-turn to keep the coil rotating. Loudspeakers and some types of microphone also use the motor effect.
当通电导体置于磁场中并受到力的作用时，就发生了电动机效应。弗莱明左手定则确定了方向：拇指——运动方向（受力方向），食指——磁场方向（N 到 S），中指——电流方向。使用更强的磁铁、更大的电流或更多处于磁场中的导线，都可以增大力的大小。简易电动机利用在两磁极间旋转的线圈工作；换向器每半圈切换一次电流方向，以维持线圈持续转动。扬声器和某些类型的话筒也利用了电动机效应。
11. Space and the Universe | 空间与宇宙
Our Solar System consists of the Sun, planets, dwarf planets, moons, asteroids and comets. Gravity provides the centripetal force that keeps planets and satellites in orbit. For a stable orbit, the gravitational force must match the required centripetal force; the orbital speed changes with distance from the Sun. A star’s life cycle depends on its mass: stars like the Sun end as white dwarfs, while more massive stars may become neutron stars or black holes. The Sun is currently a main-sequence star fusing hydrogen into helium.
我们的太阳系包括太阳、行星、矮行星、卫星、小行星和彗星。万有引力提供了维持行星和卫星轨道运动的向心力。要形成稳定轨道，引力必须等于所需的向心力；轨道速度随离太阳的距离而变化。恒星的生命周期取决于其质量：像太阳这样的恒星最终变成白矮星，而质量更大的恒星可能变成中子星或黑洞。太阳目前是一颗主序星，正将氢聚变为氦。
Evidence for the Big Bang theory comes from galactic red-shift and cosmic microwave background radiation. Red-shift is the observed increase in wavelength of light from distant galaxies, indicating they are moving away from us. The more distant a galaxy, the faster it is receding – this suggests the Universe is expanding. If the Universe began from a single point, the early hot dense state should have left behind microwave radiation, which has now cooled to about 2.7 K and is detectable in all directions. These observations support the idea that the Universe started with the Big Bang around 13.8 billion years ago.
支持大爆炸理论的证据来自星系红移和宇宙微波背景辐射。红移是指遥远星系发出的光波长变长，表明它们正在远离我们。星系越远，退行速度越快——这说明宇宙正在膨胀。如果宇宙始于一个点，早期炽热致密的状态就应该留下微波辐射，这些辐射现已冷却到约 2.7 K，在全天各个方向都能探测到。这些观测支持了宇宙约在 138 亿年前开始于大爆炸的观点。
12. Key Equations and Practical Skills | 关键方程与实验技能
Fluency with equations is non-negotiable for WJEC GCSE Physics. The following table summarises some of the most commonly examined relationships. In the exam, you will be provided with a formula sheet, but you still need to know which equation to use in which context and how to rearrange it. Always convert units before substituting numbers: for example, mass in kilograms, length in metres, time in seconds. Giving the final answer to an appropriate number of significant figures and stating the correct units will gain marks for quality of written communication.
熟练掌握公式是 WJEC GCSE 物理的基本要求。下表归纳了一些最常见的考查关系式。考试中会提供公式表，但你仍然需要知道在什么情境下使用哪个公式以及如何变形。代入数值前一定要先转换单位：比如质量用千克，长度用米，时间用秒。给出恰当有效数字的结果并注明正确单位，将有助于在书面表达质量方面得分。
| Equation | Formula | Typical Use |
|---|---|---|
| Weight | W = mg | Gravitational force on a mass |
| Speed | v = d ÷ t | Average speed or constant speed |
| Acceleration | a = (v – u) ÷ t | Uniform acceleration |
| Newton’s 2nd Law | F = ma | Resultant force, mass, acceleration |
| Momentum | p = mv | Conservation problems |
| Wave speed | v = fλ | Any wave motion |
| Energy (KE) | KE = ½mv² | Moving objects |
| Energy (GPE) | GPE = m
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