📚 Year 12 OCR Physics: Key Terms & Memory Guide | Year 12 OCR 物理：词汇术语速记指南
Mastering the vocabulary of A-Level Physics is half the battle. This bilingual guide presents the most essential terms from the Year 12 OCR Physics specification alongside clear definitions and memory tricks, so you can revise efficiently and speak the language of physics with confidence.
掌握 A-Level 物理的词汇是成功的一半。这份双语指南精选了 Year 12 OCR 物理大纲中最核心的术语，并配上清晰的定义和记忆技巧，帮助你高效复习，自信地运用物理语言。
1. Base Quantities and Units | 基本量与单位
A base quantity is a fundamental physical quantity that is defined independently, not derived from other quantities. The SI system has seven base quantities, but OCR Year 12 focuses on mass (kg), length (m), time (s), electric current (A), and temperature (K).
基本量是独立定义、不由其他量导出的基本物理量。国际单位制有七个基本量，OCR Year 12 重点关注质量（kg）、长度（m）、时间（s）、电流（A）和温度（K）。
Remember: ‘Most Large Trucks Always Klaxon’ for Mass (kg), Length (m), Time (s), Ampere (A), Kelvin (K). Homogeneity of physical equations means both sides must have the same base units – always check with dimensional analysis.
记住口诀：’Most Large Trucks Always Klaxon’ 对应质量、长度、时间、安培、开尔文。物理方程的量纲一致性意味着等式两边必须具有相同的基本单位——始终用量纲分析检查。
Prefixes like nano (10⁻⁹), micro (10⁻⁶), milli (10⁻³), centi (10⁻²), kilo (10³), mega (10⁶) are vital. Convert everything to base units before calculations to avoid order-of-magnitude errors.
词头如纳（10⁻⁹）、微（10⁻⁶）、毫（10⁻³）、厘（10⁻²）、千（10³）、兆（10⁶）至关重要。计算前将所有单位转换为基本单位，以免出现数量级错误。
2. Motion in a Straight Line | 直线运动
Displacement (s) is a vector: it measures the straight-line distance in a given direction from a reference point. Distance is a scalar – it only tells you how far you have travelled, not where you are.
位移（s）是矢量：它测量从参考点出发的直线距离和方向。路程是标量——只告诉你走了多远，不关心最终位置。
Velocity (v) = rate of change of displacement. Acceleration (a) = rate of change of velocity. The SUVAT equations link s, u, v, a, t for uniform acceleration. Link: ‘v = u + at’ is the simplest; ‘s = ut + ½ at²’ is the superhero one for finding distance when time is known.
速度（v）= 位移变化率。加速度（a）= 速度变化率。对于匀加速运动，SUVAT 方程联系了 s、u、v、a、t。记住：’v = u + at’ 最简单；’s = ut + ½ at²’ 是已知时间求距离的好帮手。
Instantaneous velocity is the gradient of a displacement–time graph; acceleration is the gradient of a velocity–time graph. The area under a velocity–time graph gives displacement. Use ‘Gradient-Area’ as a quick trigger.
瞬时速度是位移-时间图的斜率；加速度是速度-时间图的斜率。速度-时间图下的面积给出位移。用 ‘Gradient-Area’（斜率-面积）作为快速记忆点。
3. Forces and Newton’s Laws | 力与牛顿定律
Newton’s First Law: An object remains at rest or moves with constant velocity unless acted upon by a resultant force. Inertia is the resistance to a change in velocity – mass is the measure of inertia.
牛顿第一定律：除非受合外力作用，物体将保持静止或匀速直线运动状态。惯性是抵抗速度变化的性质——质量是惯性的量度。
Newton’s Second Law: ΣF = m a. Resultant force is directly proportional to acceleration, with mass as the constant. Remember: ‘Force = ma’ makes sense, but the strength is that a = F/m, so a big mass means small acceleration for the same force.
牛顿第二定律：ΣF = m a。合外力与加速度成正比，质量是比例常数。记住：F=ma，但更深刻的是 a = F/m，因此相同力下质量越大加速度越小。
Newton’s Third Law: If body A exerts a force on body B, B exerts an equal and opposite force on A. These forces are of the same type, on different bodies. Term: ‘Action–reaction pair’. Never cancel because they act on different objects.
牛顿第三定律：若物体 A 对物体 B 施加力，B 同时对 A 施加等大反向的力。这两个力类型相同，作用在不同物体上。术语：’作用力与反作用力对’。它们永远不抵消，因为作用对象不同。
Weight (W = mg) is the gravitational force; normal contact force is perpendicular to the surface; friction opposes motion or attempted motion. Tension is the force transmitted by a string or cable.
重量（W = mg）是万有引力；法向接触力垂直于表面；摩擦力阻碍运动或运动趋势。张力是通过绳子或电缆传递的力。
4. Work, Energy, and Power | 功、能与功率
Work done (W) = F s cos θ, measured in joules (J). When force and displacement are parallel, W = F s. Work is the transfer of energy by means of a force. Energy is the capacity to do work.
做功（W）= F s cos θ，单位焦耳（J）。当力与位移平行时，W = F s。功是通过力实现的能量转移。能量是做功的能力。
Kinetic energy Eₖ = ½ m v². Gravitational potential energy Eₚ = m g Δh. The principle of conservation of energy states that energy cannot be created or destroyed, only transferred between stores.
动能 Eₖ = ½ m v²。重力势能 Eₚ = m g Δh。能量守恒定律指出，能量不能被创造或消灭，只能在不同的能量贮存间转移。
Power (P) = work done / time taken = energy transferred / time, unit watt (W). P = F v for a constant force moving at speed v. Efficiency = (useful energy output / total energy input) × 100%.
功率（P）= 做功/时间 = 能量转移/时间，单位瓦特（W）。对于恒力以速度 v 移动，P = F v。效率 = （有用输出能量/总输入能量）× 100%。
5. Materials and Hooke’s Law | 材料与胡克定律
Hooke’s Law: For a spring or wire, extension (Δx) is directly proportional to the applied force (F) up to the limit of proportionality, i.e., F = k Δx, where k is the spring constant (N m⁻¹).
胡克定律：对于弹簧或金属丝，在比例极限内，伸长量（Δx）与施加的力（F）成正比，即 F = k Δx，其中 k 为劲度系数（N m⁻¹）。
The elastic limit is the point beyond which the material will no longer return to its original shape when the load is removed – permanent deformation occurs. Elastic strain energy stored = area under F–x graph = ½ F Δx for a Hookean material.
弹性极限是材料在撤去负载后不再恢复原状的临界点——发生永久形变。储存的弹性应变能 = F-x 图下方面积 = 对于线弹性材料为 ½ F Δx。
Key terms from a stress–strain graph: stress (σ = F/A, unit Pa), strain (ε = ΔL/L₀, no units), Young modulus (E = σ/ε). Remember: ‘Young = stress over strain’ – a measure of stiffness. Brittle materials break with little plastic deformation; ductile materials stretch significantly before breaking.
应力-应变图中的关键术语：应力（σ = F/A，单位 Pa），应变（ε = ΔL/L₀，无单位），杨氏模量（E = σ/ε）。记住：’Young = 应力除以应变’——衡量刚度。脆性材料在很少塑性变形下断裂；延性材料在断裂前可显著拉伸。
6. Waves: Basic Properties | 波的基本性质
A progressive wave transfers energy from one point to another without transferring matter. Displacement (x) at a point is the distance and direction it has moved from equilibrium. Amplitude (A) is the maximum displacement.
行波将能量从一点传输到另一点而不传递物质。某点的位移（x）是它相对于平衡位置移动的距离和方向。振幅（A）是最大位移。
Wavelength (λ) is the distance between two consecutive points in phase, e.g., crest to crest. Frequency (f) is the number of complete oscillations per second (Hz). Period (T) = 1/f. Wave speed v = f λ.
波长（λ）是相邻两个同相位点之间的距离，如波峰到波峰。频率（f）是每秒完整振荡的次数（Hz）。周期（T）= 1/f。波速 v = f λ。
Transverse waves: oscillations are perpendicular to direction of energy transfer (light, water ripples). Longitudinal waves: oscillations are parallel (sound). Remember ‘T for transverse, T for perpendicular’ if you imagine the ‘t’ shape.
横波：振动方向垂直于能量传递方向（光、水波涟漪）。纵波：振动方向平行（声音）。可记 ‘T for transverse, T for perpendicular’ 想象 ‘t’ 形状是垂直的。
Phase difference φ describes how much one wave lags behind another, measured in radians or degrees. Coherence: two waves have the same frequency and constant phase difference – essential for interference.
相位差 φ 描述一个波落后另一个波的程度，以弧度或度衡量。相干性：两列波频率相同、相位差恒定——是干涉的基本条件。
7. Superposition and Interference | 叠加与干涉
Principle of superposition: when two or more waves meet at a point, the resultant displacement is the vector sum of the individual displacements. Constructive interference: waves in phase → amplitude increases. Destructive: antiphase (180° out of phase) → amplitude decreases or cancels.
叠加原理：当两列或更多列波在某点相遇时，合位移是各位移的矢量总和。相长干涉：波同相→振幅增大。相消干涉：反相（相差180°）→振幅减小或抵消。
Stationary (standing) waves form when two identical progressive waves travelling in opposite directions superpose. Nodes: points of zero displacement. Antinodes: points of maximum displacement. Adjacent nodes are separated by λ/2.
驻波由两列相同行波沿相反方向传播叠加而形成。波节：位移恒为零的点。波腹：振幅最大的点。相邻波节间距为 λ/2。
Young’s double-slit experiment demonstrates interference of light. Fringe spacing w = λ D / s, where D is distance from slits to screen, s is slit separation. Use ‘Wavelength times Distance over Slit spacing’ to recall w = λD/s.
杨氏双缝实验证明了光的干涉。条纹间距 w = λ D / s，其中 D 为双缝到屏幕的距离，s 为缝间距。用 ‘波长乘距离除以缝间距’ 记忆 w = λD/s。
8. Electricity: Current and Circuits | 电流与电路
Electric current (I) is the rate of flow of charge: I = ΔQ / Δt. Unit: ampere (A). Conventional current flows from positive to negative – this is the direction that positive charges would move, opposite to electron flow.
电流（I）是电荷流动的速率：I = ΔQ / Δt。单位：安培（A）。约定电流方向从正到负——这是正电荷移动的方向，与电子流动方向相反。
Potential difference (p.d., V) between two points is the energy transferred per unit charge: V = W/Q. Electromotive force (e.m.f.) is the energy supplied by a source per unit charge. A volt is a joule per coulomb.
两点之间的电势差（p.d., V）是每单位电荷转移的能量：V = W/Q。电动势（e.m.f.）是电源每单位电荷提供的能量。伏特即焦耳每库仑。
Resistance (R) = V / I, unit ohm (Ω). Ohm’s Law: for an ohmic conductor at constant temperature, V ∝ I. Ohmic components (e.g., fixed resistor) give a straight V–I line through origin. Filament lamps and diodes are non-ohmic.
电阻（R）= V / I，单位欧姆（Ω）。欧姆定律：对于恒温下的欧姆导体，V ∝ I。欧姆元件（如固定电阻器）的 V-I 图是一条过原点的直线。灯丝灯泡和二极管是非欧姆的。
9. Resistance and Ohm’s Law | 电阻与欧姆定律
Resistivity (ρ) is an intrinsic property of a material: R = ρ L / A, where L is length, A is cross-sectional area. Unit: Ω m. Resistivity depends on material and temperature, not on dimensions.
电阻率（ρ）是材料的内禀属性：R = ρ L / A，其中 L 是长度，A 是横截面积。单位：Ω m。电阻率取决于材料和温度，而与尺寸无关。
In a series circuit, current is the same everywhere, total resistance R_total = R₁ + R₂ + … . In parallel, the p.d. across each branch is the same, and 1/R_total = 1/R₁ + 1/R₂ + … . Use ‘series shares current, parallel shares voltage’ as a fast reminder.
串联电路中，各处电流相同，总电阻 R_total = R₁ + R₂ + … 。并联电路中，各支路电压相同，1/R_total = 1/R₁ + 1/R₂ + … 。用 ‘串联共电流，并联共电压’ 快速记忆。
Power in electrical circuits: P = I V = I² R = V² / R. Always check which forms use constant current or constant voltage to decide which heating effect dominates.
电功率：P = I V = I² R = V² / R。注意恒流或恒压情况下采取哪种形式判断热效应。
10. Quantum Phenomena: Photons and Electrons | 量子现象：光子与电子
Photon model: electromagnetic radiation is composed of packets (quanta) called photons. Energy of a photon E = h f, where h is Planck’s constant. Higher frequency = more energetic photons.
光子模型：电磁辐射由称为光子的能量包（量子）组成。光子能量 E = h f，其中 h 为普朗克常数。频率越高，光子能量越大。
The photoelectric effect: emission of electrons from a metal surface when light of frequency above a certain threshold shines on it. Key findings: emission is instantaneous; there is a threshold frequency f₀; rate of emission depends on intensity; maximum kinetic energy depends only on frequency (not intensity).
光电效应：当频率高于某一阈值的照射到金属表面时，电子被发射出来。关键发现：发射是瞬时的；存在截止频率 f₀；发射速率取决于光强；最大动能只取决于频率（而不取决于光强）。
Einstein’s photoelectric equation: h f = Φ + KE_max. Here Φ (work function) is the minimum energy needed to release an electron. Use ‘hf = phi + K’ to remember. Stopping potential V_s stops even the most energetic electrons: e V_s = KE_max.
爱因斯坦光电方程：h f = Φ + KE_max。其中 Φ（逸出功）是释放电子所需的最小能量。用 ‘hf = Φ + K’ 记忆。遏止电压 V_s 能使最大动能的电子停止：e V_s = KE_max。
Wave–particle duality: light shows diffraction (wave-like) and the photoelectric effect (particle-like). De Broglie wavelength λ = h / p, where p is momentum, suggests matter also has wave properties. Electron diffraction confirms this.
波粒二象性：光表现出衍射（波性）和光电效应（粒性）。德布罗意波长 λ = h / p，其中 p 为动量，表明物质也具有波性。电子衍射证实了这一点。
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