📚 Year 13 CAIE Physics: Quick Memorisation Guide to Key Terms | A2 物理核心术语速记指南
Mastering A2 Physics requires more than just problem-solving — it demands precise recall of a vast technical vocabulary. Words like ‘centripetal’, ‘capacitive reactance’, or ‘binding energy per nucleon’ can blur together under exam pressure. This guide breaks down the most commonly confused terms topic by topic, pairing clear definitions with memory hooks so you can recall them fast and use them accurately in CAIE exam questions.
攻克 A2 物理不仅需要解题技巧，更需要对大量术语的精准记忆。诸如“向心”、“容抗”或“比结合能”这类词汇，在考试压力下很容易混淆。本指南按主题梳理最易混淆的核心术语，用清晰的定义搭配记忆钩子，帮助你在 CAIE 考题中快速提取并准确使用。
1. Circular Motion and Gravitational Fields | 圆周运动与引力场
Centripetal force: The resultant force directed towards the centre of a circle, causing an object to move in a circular path. It is not a new force but the net effect of forces like tension, gravity or friction. Remember: ‘centripetal’ sounds like ‘centre-seeking’. The formula is F = mv²/r = mrω², where ω is angular velocity.
向心力：指向圆心的合力，使物体沿圆周运动。它并非某种新型力，而是拉力、引力或摩擦力等的净效果。记忆关键：“向心”即“指向中心”。公式为 F = mv²/r = mrω²，其中 ω 为角速度。
Gravitational potential at a point is the work done per unit mass to bring a small test mass from infinity to that point. It is always negative, approaching zero at infinity. Think: the deeper you are in a gravitational well, the more negative the potential. V = -GM/r.
引力势：将单位质量检验物体从无穷远移至某点所做的功。其值恒为负，在无穷远处趋近于零。想象越深入引力势阱，势越负。V = -GM/r。
Geostationary orbit: An equatorial orbit with a period of 24 hours, so the satellite appears stationary above a fixed point on Earth. Use ‘geo’ (Earth) + ‘stationary’ (stays put). Must satisfy r³ = GMT²/(4π²) with T = 24 h.
地球同步轨道：周期为 24 小时的赤道轨道，卫星看似悬停在地球某固定点上空。“geo” 指地球，“stationary” 指不动。满足 r³ = GMT²/(4π²)，T = 24 小时。
2. Simple Harmonic Motion | 简谐运动
Simple harmonic motion (SHM): Oscillatory motion where acceleration is directly proportional to displacement from equilibrium and always directed towards equilibrium. The signature equation is a = -ω²x. The negative sign signals restoring force — like a spring pulling back.
简谐运动 (SHM)：加速度与离开平衡位置的位移成正比且始终指向平衡位置的振动。标志性方程 a = -ω²x。负号代表恢复力——正如弹簧回拉。
Damping: The gradual loss of amplitude due to resistive forces. Light damping gives a slow decay; critical damping brings the system to rest in the shortest time without oscillation; heavy damping overslows the return. Picture a car suspension: critical damping is the ideal.
阻尼：振幅因阻力而逐渐衰减。轻阻尼缓慢衰减；临界阻尼使系统在最短时间内无震荡地停稳；过阻尼则过度缓慢。想象汽车悬挂：临界阻尼最为理想。
Resonance: When the driving frequency matches the natural frequency, amplitude peaks dramatically. Famous example: soldiers marching break step on a bridge. Remember ‘resonance’ = ‘re-sound’ — energy feeds in at just the right rhythm.
共振：当驱动频率等于固有频率时，振幅剧烈增大。著名例子：士兵过桥便步走。记忆：“共振”即“再次发声”——能量以恰好的节奏输入。
3. Thermal Physics | 热力学关键量
Specific heat capacity (c): Energy needed to raise the temperature of 1 kg of a substance by 1 K, without phase change. Unit: J kg⁻¹ K⁻¹. Mnemonic: ‘specific’ means per kilogram; ‘capacity’ suggests how much energy the substance can ‘hold’ per degree.
比热容 (c)：使 1 kg 物质温度升高 1 K 所需的能量，无相变。单位：J kg⁻¹ K⁻¹。记忆：“比”指每千克；“容”暗示每度能“容纳”多少能量。
Specific latent heat (L): Energy required to change the phase of 1 kg of a substance at constant temperature. Latent heat of fusion (melting) and vaporisation (boiling). ‘Latent’ means hidden — the energy goes into breaking bonds, not raising temperature.
比潜热 (L)：使 1 kg 物质在恒温下发生相变所需的能量。熔解潜热和汽化潜热。“潜”指隐藏——能量用于打破键合，而非升温。
Internal energy: The sum of the randomly distributed kinetic and potential energies of all molecules in a system. For an ideal gas, internal energy depends only on temperature because there are no intermolecular forces (potential = 0). Think of a gas as a swarm of bouncing particles.
内能：系统内所有分子无规则分布的动能和势能之和。对理想气体，内能仅依赖于温度，因为分子间无作用力（势能为零）。想象气体就是一群弹跳的粒子。
4. Ideal Gases | 理想气体定律与微观解释
Equation of state for an ideal gas: pV = nRT (moles) or pV = NkT (molecules), where k is the Boltzmann constant. The law combines Boyle’s, Charles’s and the pressure law. Memory aid: ‘pV equals nRT’ – pronounce it like ‘privet’ to make it stick.
理想气体状态方程：pV = nRT（摩尔）或 pV = NkT（分子数），k 为玻尔兹曼常量。该定律综合了玻意耳定律、查理定律和压强定律。记忆法：“pV nRT” 连读像“private”。
Kinetic theory assumption: Gas consists of a large number of identical, tiny particles in random, rapid motion. All collisions are perfectly elastic. No intermolecular forces except during collisions. Visualise them as perfectly bouncy ping-pong balls.
分子运动论假设：气体由大量相同微小粒子组成，作无规则快速运动。所有碰撞均为完全弹性碰撞。除碰撞瞬间外无分子间力。想象成完美的弹力乒乓 balls。
Root mean square speed (c_rms): √(⟨c²⟩) = √(3kT/m) = √(3RT/M). It represents a typical molecular speed. The ‘rms’ average is greater than the mean speed due to the squaring. Link: high temperature → faster molecules.
方均根速率 (c_rms)：√(⟨c²⟩) = √(3kT/m) = √(3RT/M)。代表一个典型分子速率。由于先平方再平均，rms 值大于平均速率。联系：温度越高，分子越快。
5. Electric Fields and Capacitance | 电场与电容
Electric field strength (E): Force per unit positive charge. For a point charge, E = Q/(4πε₀r²). For a uniform field, E = V/d. The key direction: away from positive, towards negative. Imagine tiny positive test charges feeling the push.
电场强度 (E)：单位正电荷所受的力。点电荷场：E = Q/(4πε₀r²)；匀强场：E = V/d。方向要点：背离正电荷，指向负电荷。想象微小正检验电荷感受到推力。
Electric potential (V): Work done per unit charge to bring a positive test charge from infinity to a point. V = Q/(4πε₀r). Unlike field strength, potential is a scalar. Remember: potential is to charge what height is to mass in gravity.
电势 (V)：将单位正电荷从无穷远移至某点所做的功。V = Q/(4πε₀r)。与场强不同，电势是标量。记忆：电势之于电荷，犹如高度之于质量。
Capacitance (C): Charge stored per unit potential difference, C = Q/V. A capacitor stores energy in the electric field. Think of it as a charge bucket — bigger capacitance can hold more charge for the same voltage. For a parallel plate, C = εA/d.
电容 (C)：单位电势差下储存的电荷量，C = Q/V。电容器在电场中储能。把它想成电荷水桶——电容越大，相同电压下能容纳的电荷越多。平行板电容器 C = εA/d。
Time constant (τ = RC): The time for the charge/voltage/current to fall to 1/e (about 37%) of its initial value during discharge. In CR circuits, after 5τ the capacitor is practically fully charged/discharged. Link: ‘rest and charge’ → RC.
时间常数 (τ = RC)：放电时电荷/电压/电流衰减至初始值 1/e（约 37%）所需的时间。在 RC 回路中，5τ 后电容几乎完全充/放电。联想：’rest and charge’ 首字母 RC。
6. Magnetic Fields and Electromagnetic Induction | 磁场与电磁感应
Magnetic flux density (B): Defined by F = BIL sinθ for a current‑carrying conductor. Unit: tesla (T). B‑fields are visualised with lines from north to south. Remember ‘B’ as ‘field strength’ felt by moving charges.
磁通量密度 (B)：由通电导线受力 F = BIL sinθ 定义。单位：特斯拉 (T)。磁感线从 N 极指向 S 极。记住“B”即运动电荷感受到的“场强”。
Magnetic flux (Φ): Φ = BA cosθ, the component of B perpendicular to area A. Unit: weber (Wb). The ‘cosθ’ is key — flux changes when a coil rotates, inducing emf.
磁通量 (Φ)：Φ = BA cosθ，即 B 垂直于面积 A 的分量。单位：韦伯 (Wb)。“cosθ”很关键——线圈转动时磁通变化，从而感应出电动势。
Faraday’s law and Lenz’s law: Induced emf ε = -dΦ/dt. The negative sign embodies Lenz’s law — the induced current opposes the change that produced it. Mnemonic: ‘Lenz loves to oppose’. That minus sign is the reason generators require work.
法拉第定律与楞次定律：感应电动势 ε = -dΦ/dt。负号体现了楞次定律——感应电流反抗引起它的变化。记忆：“楞次喜欢反抗”。这个负号解释了发电机为何需做机械功。
7. Alternating Currents | 交流电
RMS value: The root mean square of an alternating quantity. For a sinusoidal voltage, V_rms = V₀/√2. It’s the equivalent DC value that delivers the same heating power. ‘RMS’ = ‘Really Mean Square’ — you square, mean, then root.
方均根值：交流量的均方根。对正弦电压，V_rms = V₀/√2。它是能产生相同热功率的等效直流值。RMS 流程：平方、平均、再开根。
Transformer: A device using mutual induction to step up or down AC voltage. V_s/V_p = N_s/N_p. For an ideal transformer, input power equals output power. Remember: turns ratio changes voltage; current changes inversely.
变压器：利用互感升高或降低交流电压的装置。V_s/V_p = N_s/N_p。理想变压器输入功率等于输出功率。匝数比改变电压；电流反向变化。
Rectification: Converting AC to DC. Half‑wave rectification uses one diode; full‑wave uses a bridge of four diodes, giving a smoother output. Smoothing is then done by a capacitor in parallel. ‘Rectify’ means to correct the direction.
整流：将交流转为直流。半波整流用一只二极管；全波用四只二极管桥式接法，输出更平缓。后续并联电容进行滤波。“整流”即校正方向。
8. Quantum Physics | 量子物理基石
Photoelectric effect: Emission of electrons from a metal surface when light of sufficiently high frequency strikes it. Key findings: threshold frequency exists, maximum kinetic energy depends on frequency not intensity. Einstein’s equation: hf = Φ + K_max.
光电效应：足够高频率的光照射金属表面时，电子逸出的现象。关键：存在截止频率；最大动能取决于频率而非光强。爱因斯坦方程：hf = Φ + K_max。
Photon: A quantum of electromagnetic energy, E = hf. Light is both wave and particle — the photon model explains instantaneous emission. Think of a photon as a tiny energy packet hitting an electron like a snooker ball.
光子：电磁能的量子，E = hf。光兼具波粒二象性——光子模型解释了瞬时发射。把光子想象成撞击电子的微小能量包，如同台球。
De Broglie wavelength: λ = h/p = h/(mv). Matter has wave‑like properties. This is proven by electron diffraction. Memorise ‘de Broglie = p and λ’ — momentum and wavelength are inversely linked.
德布罗意波长：λ = h/p = h/(mv)。物质具有波动性，电子衍射可证实。记忆：“德布罗意=动量与波长”——波长与动量成反比。
9. Nuclear Physics | 核物理术语
Mass defect: The difference between the mass of a nucleus and the sum of the masses of its individual nucleons. This ‘missing’ mass is converted into binding energy via ΔE = Δmc². Think: when nucleons bond, they give up mass to gain stability.
质量亏损：原子核质量与其各核子质量总和之差。这部分“失踪”的质量通过 ΔE = Δmc² 转化为结合能。想象：核子结合时失去质量以换取稳定。
Binding energy per nucleon: Total binding energy divided by the nucleon number. This graph peaks at iron‑56, the most stable nucleus. A higher value means a tighter, more stable nucleus. Remember: ‘B.E. per nucleon’ estimates how much energy you’d get out by pulling nucleons apart.
比结合能：总结合能除以核子数。该曲线在铁-56 处达到峰值，铁最稳定。比结合能越高，原子核越紧密稳定。联想：拉开每个核子需消耗的能量。
Radioactive decay law: A = λN, where A is activity, λ the decay constant. The number of undecayed nuclei follows N = N₀ e⁻λt. Half‑life T₁/₂ = ln2/λ. Decay is spontaneous and random — individual nuclei decay without any external trigger.
放射性衰变定律：A = λN，A 为活度，λ 为衰变常量。未衰变核数满足 N = N₀ e⁻λt。半衰期 T₁/₂ = ln2/λ。衰变是自发的和随机的——单个核无需任何外界触发。
10. Medical Imaging | 医学成像
X‑ray production: Electrons are accelerated through a high voltage and strike a metal target. Most energy becomes heat, but a few photons are emitted as bremsstrahlung (braking radiation) and characteristic X‑rays. The spectrum is continuous with sharp peaks. Remember: ‘braking’ makes X‑rays.
X 射线产生：电子经高电压加速后轰击金属靶。大部分能量变为热，少量以韧致辐射和特征 X 射线形式发射。谱线连续且有尖峰。记忆：“制动”产生 X 射线。
Ultrasound: Sound waves with frequency above 20 kHz. Used for imaging via pulse‑echo technique. A piezoelectric transducer both emits and receives ultrasound. Acoustic impedance Z = ρc explains reflection at boundaries. ‘Ultra’ means beyond, so ultrasound is beyond human hearing.
超声波：频率高于 20 kHz 的声波，利用脉冲回波技术成像。压电换能器负责发射和接收超声波。声阻抗 Z = ρc 解释了界面处的反射。“ultra”意为超越，超声波即超越人耳听力范围。
PET scan: Positron Emission Tomography. A positron‑emitting tracer is injected; annihilation with an electron produces two gamma photons travelling in opposite directions. Detecting coincident photons builds a 3D image. ‘PET’ hints the tracer is ‘positron’ based.
PET 扫描：正电子发射断层成像。注入正电子发射示踪剂；与电子湮灭产生两个背向而行的 γ 光子。探测符合事件构建三维影像。“PET”提示示踪剂基于正电子。
11. Astronomy and Cosmology | 天文学与宇宙学
Luminosity: Total power radiated by a star. Related to apparent brightness b via b = L/(4πd²). Think: a light bulb’s brightness drops with distance squared. Absolute magnitude relates to luminosity.
光度：恒星辐射的总功率。与视亮度的关系为 b = L/(4πd²)。想象灯泡的亮度随距离平方衰减。绝对星等与光度相关。
Redshift and Hubble’s law: For a receding galaxy, observed wavelength λ_obs > λ_rest; redshift z = Δλ/λ. Hubble’s law: v = H₀ d, where H₀ is the Hubble constant. The expanding universe stretches light waves. ‘Red’ shift means stretched towards longer wavelengths.
红移与哈勃定律：对退行星系，观测波长 λ_obs > 静止波长 λ_rest；红移 z = Δλ/λ。哈勃定律：v = H₀ d，H₀ 为哈勃常数。膨胀宇宙拉伸光波。“红”移即波长拉长朝红色端移动。
Cosmic microwave background (CMB): The remnant radiation from the Big Bang, now at about 2.7 K. It peaks in the microwave region, providing strong evidence for a hot early universe. Think of it as the faint afterglow of creation.
宇宙微波背景辐射 (CMB)：大爆炸的残余辐射，现已冷却至约 2.7 K，在微波波段达峰值，为早期炽热宇宙提供了有力证据。将其想象为创世的微弱余晖。
Dark energy: A hypothetical form of energy that permeates all space and accelerates the expansion of the universe. It opposes gravity on cosmic scales. Though unseen, its presence is inferred from Type Ia supernova observations.
暗能量：一种假设中充塞宇宙、驱动宇宙加速膨胀的能量形式。在宇观尺度上与引力相抗。虽不可见，但通过 Ia 型超新星观测可推知其存在。
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