AQA AS Physics Subject-Specific Vocabulary — AQA AS 物理学科专用词汇精讲

AQA AS 物理考试中，很多失分并不是因为不会做题，而是因为考生对题面中的专业术语理解不准、表述不规范。物理学科有一套精确的词汇体系，同一个词（比如”velocity”和”speed”、”accuracy”和”precision”）在物理中有着严格而不同的含义。本文按照 AQA 考试大纲的顺序，系统梳理 AS 阶段最核心的物理术语，帮助你在答题时用词准确、拿到术语分。

In AQA AS Physics, many marks are lost not because students cannot do the calculations, but because they misunderstand the precise technical terms used in the questions. Physics has a rigorous vocabulary, and similar-sounding words such as “velocity” and “speed”, or “accuracy” and “precision”, carry strict and distinct meanings. This article works through the most important AS-level terms in the order of the AQA specification, so you can use language accurately and secure the terminology marks.

1. 国际单位制基本单位：质量、长度、时间与电流 | SI Base Units: Mass, Length, Time and Current

国际单位制（SI）建立在七个基本单位之上。AS 阶段你最常用到的是六个：质量用千克（kg）、长度用米（m）、时间用秒（s）、电流用安培（A）、热力学温度用开尔文（K）、物质的量用摩尔（mol）。第七个是发光强度坎德拉（cd），在 AS 物理中较少涉及。记住这些基本单位的符号必须小写，只有以人名命名的单位符号才大写（如安培 A、开尔文 K）。

The International System of Units (SI) is built on seven base units. At AS level you will most often use six of them: mass in kilograms (kg), length in metres (m), time in seconds (s), electric current in amperes (A), thermodynamic temperature in kelvin (K), and amount of substance in moles (mol). The seventh, luminous intensity in candelas (cd), rarely appears in AS Physics. Note that unit symbols are written in lower case, except those named after people (ampere A, kelvin K).

物理量 | Quantity	基本单位 | Base Unit	符号 | Symbol
质量 Mass	千克 kilogram	kg
长度 Length	米 metre	m
时间 Time	秒 second	s
电流 Electric current	安培 ampere	A
热力学温度 Thermodynamic temperature	开尔文 kelvin	K
物质的量 Amount of substance	摩尔 mole	mol

考试中常考”判断某个量是基本量还是导出量”。记住一个判据：凡是能用基本单位组合表示的量，都是导出量。例如牛顿（N）可以写成 kg m s⁻²，所以力是导出量，不是基本量。

A common exam task is deciding whether a quantity is a base quantity or a derived quantity. The test is simple: if a quantity can be expressed as a combination of base units, it is derived. For example, the newton (N) can be written as kg m s⁻², so force is a derived quantity, not a base quantity.

2. 导出单位与量纲一致性：用单位检验方程 | Derived Units and Dimensional Homogeneity: Checking Equations with Units

导出单位由基本单位组合而来。速度的单位是 m s⁻¹，加速度是 m s⁻²，力的单位牛顿是 kg m s⁻²，能量和功的单位焦耳是 kg m² s⁻²。把它们展开成基本单位的过程，叫做”用基本单位表示”（express in base units），这是 AQA 考试中反复出现的题型。

Derived units are built from combinations of base units. Speed is measured in m s⁻¹, acceleration in m s⁻², force (newton) in kg m s⁻², and energy or work (joule) in kg m² s⁻². Writing them out in base units is called “expressing a quantity in base units”, and it is a recurring question type in AQA papers.

量纲一致性（homogeneity）是检验物理方程是否成立的有力工具。一个物理上正确的方程，等号两边必须具有相同的单位。例如验证 F = ma，左边单位是 kg m s⁻²，右边是 kg × m s⁻²，二者一致，说明该方程在量纲上是成立的。如果一个方程的等号两边单位不同，那么它一定是错误的。

Homogeneity of units is a powerful tool for checking whether a physical equation is valid. In a physically correct equation, both sides must have the same units. For example, to verify F = ma, the left side has units kg m s⁻² and the right side has kg × m s⁻²; they match, so the equation is dimensionally valid. If the two sides of an equation have different units, the equation must be wrong.

3. SI 词头与数量级：从太拉到飞米 | SI Prefixes and Orders of Magnitude: From Tera to Femto

SI 词头用来表示很大或很小的数量，避免写出冗长的小数。AS 阶段必须熟记的词头包括：太拉 T（10¹²）、吉咖 G（10⁹）、兆 M（10⁶）、千 k（10³）、厘 c（10⁻²）、毫 m（10⁻³）、微 μ（10⁻⁶）、纳 n（10⁻⁹）、皮 p（10⁻¹²）和飞 f（10⁻¹⁵）。注意大小写区别：兆 M 是大写，而毫 m 是小写，二者相差九个数量级。

SI prefixes express very large or very small numbers so that you do not have to write long decimal strings. At AS level you must know: tera T (10¹²), giga G (10⁹), mega M (10⁶), kilo k (10³), centi c (10⁻²), milli m (10⁻³), micro μ (10⁻⁶), nano n (10⁻⁹), pico p (10⁻¹²) and femto f (10⁻¹⁵). Watch the capitalisation: mega is a capital M while milli is a lower-case m; they differ by nine orders of magnitude.

词头 | Prefix	符号 | Symbol	倍率 | Factor
太拉 tera	T	10¹²
吉咖 giga	G	10⁹
兆 mega	M	10⁶
千 kilo	k	10³
厘 centi	c	10⁻²
毫 milli	m	10⁻³
微 micro	μ	10⁻⁶
纳 nano	n	10⁻⁹
皮 pico	p	10⁻¹²
飞 femto	f	10⁻¹⁵

换算时先写出指数形式再处理词头，是最不容易出错的方法。例如把 2500 nm 换算成米：2500 nm = 2500 × 10⁻⁹ m = 2.5 × 10⁻⁶ m。数量级（order of magnitude）指的是一个量最接近的 10 的幂，通常用它来快速比较两个量的大小。

The least error-prone way to convert is to write the number in power-of-ten form first, then handle the prefix. For example, to convert 2500 nm into metres: 2500 nm = 2500 × 10⁻⁹ m = 2.5 × 10⁻⁶ m. The order of magnitude of a quantity is the power of ten closest to it, and it is used to compare two quantities quickly.

4. 标量与矢量：距离与位移、速率与速度的区别 | Scalars and Vectors: Distance vs Displacement, Speed vs Velocity

标量（scalar）只有大小，没有方向，例如质量、时间、温度、能量、距离和速率。矢量（vector）既有大小又有方向，例如位移、速度、加速度、力、动量和电场强度。区分这两类量是 AQA AS 物理的基础考点。

A scalar has magnitude only and no direction, for example mass, time, temperature, energy, distance and speed. A vector has both magnitude and direction, for example displacement, velocity, acceleration, force, momentum and electric field strength. Distinguishing these two categories is a foundational skill in AQA AS Physics.

最容易混淆的一对词是 distance（距离，标量）与 displacement（位移，矢量），以及 speed（速率，标量）与 velocity（速度，矢量）。物体绕操场跑一圈回到起点，走过的距离是操场周长，但位移是零，因为起点和终点重合。同样地，匀速圆周运动中速率恒定，但速度方向不断变化，所以速度并不恒定。

The most easily confused pairs are distance (scalar) versus displacement (vector), and speed (scalar) versus velocity (vector). If you run one lap of a track and return to the start, the distance travelled is the track perimeter, but the displacement is zero because the start and end points coincide. Likewise, in uniform circular motion the speed is constant but the direction of the velocity keeps changing, so the velocity is not constant.

5. 测量术语：准确度、精密度、分辨率与不确定度 | Measurement Terms: Accuracy, Precision, Resolution and Uncertainty

这四个词在 AQA 考试中经常被用来判断实验测量的质量，含义各不相同。准确度（accuracy）描述测量值接近真值的程度；精密度（precision）描述多次测量结果彼此接近的程度。一组测量可以精密但不准确（例如存在系统误差），也可以准确但不精密（例如随机误差很大）。

These four words are used regularly in AQA questions to judge the quality of experimental measurements, and they mean different things. Accuracy describes how close a measured value is to the true value; precision describes how close repeated measurements are to each other. A set of measurements can be precise but inaccurate (for example, when a systematic error is present), or accurate but not precise (when random errors are large).

分辨率（resolution）是仪器能显示的最小刻度变化，例如一把尺子的分辨率是 1 mm，一个量角器的分辨率是 1°。不确定度（uncertainty）表示测量值的可能变动范围，常用”±”表示。对于单次读数，绝对不确定度通常取最小刻度的一半；对于多次重复测量，绝对不确定度取测量值范围的一半（即最大值与最小值之差的一半）。

Resolution is the smallest change in a quantity that an instrument can display, for example a ruler has a resolution of 1 mm and a protractor has a resolution of 1°. Uncertainty expresses the range within which the true value is likely to lie, written with a “±” sign. For a single reading, the absolute uncertainty is usually half the smallest scale division; for repeated readings, it is half the range of the measurements (half the difference between the largest and smallest values).

6. 系统误差与随机误差：如何识别并减小误差 | Systematic and Random Errors: Identifying and Reducing Them

系统误差（systematic error）使所有测量值都朝同一方向偏离真值，例如仪器没有调零、秒表总是走得慢、或者测量方法本身有缺陷（如从读数中央而不是底部读液面）。系统误差的特点是重复测量无法消除，因为它每次都朝同一个方向偏。它影响测量的准确度，但不影响精密度。

A systematic error shifts every reading away from the true value in the same direction, for example an instrument that is not zeroed, a stopwatch that always runs slow, or a flawed method (such as reading a liquid level from the wrong point). The key feature of a systematic error is that repeating the measurement does not remove it, because it biases every reading the same way. It affects accuracy but not precision.

随机误差（random error）使测量值随机地分布在真值两侧，来源于读数时的判断误差、环境的微小波动等。随机误差可以通过多次测量并取平均值来减小。减小系统误差要靠改进仪器或方法（如重新调零、使用更准确的仪器）。考试中常问”重复测量能减小哪种误差”，答案是随机误差，而不是系统误差。

Random errors scatter readings randomly on either side of the true value, arising from judgement when reading an instrument or from small environmental fluctuations. They can be reduced by taking repeat readings and finding the mean. Systematic errors are reduced by improving the apparatus or method (re-zeroing the instrument, using a more accurate device). A common exam question asks which type of error is reduced by repeating measurements; the answer is random error, not systematic error.

7. 力学核心术语：位移、速度、加速度与牛顿定律 | Core Mechanics Terms: Displacement, Velocity, Acceleration and Newton’s Laws

加速度（acceleration）是速度的变化率，即单位时间内速度的变化量，单位是 m s⁻²。注意”减速”在物理中同样是加速度，只是方向与速度相反，称为负加速度。牛顿第二定律 F = ma 表明，合力等于质量乘以加速度，这是把力、质量和运动联系起来的核心方程。

Acceleration is the rate of change of velocity, the change in velocity per unit time, measured in m s⁻². Note that “slowing down” is still acceleration in physics; the acceleration simply points opposite to the velocity and is called negative acceleration. Newton’s second law, F = ma, states that the resultant force equals mass times acceleration, and it is the central equation linking force, mass and motion.

动量（momentum）定义为质量乘以速度，即 p = mv，单位是 kg m s⁻¹，它是矢量。冲量（impulse）是力乘以作用时间，等于动量的变化量。在碰撞问题中，动量守恒定律（如果系统不受外力）是解题的关键工具。合力（resultant force）指作用在物体上所有力的矢量和，当合力为零时物体处于平衡状态。

Momentum is defined as mass times velocity, p = mv, with units kg m s⁻¹, and it is a vector. Impulse is force multiplied by the time for which it acts, and it equals the change in momentum. In collision problems, the law of conservation of momentum (when no external resultant force acts) is the key tool. The resultant force is the vector sum of all forces acting on an object; when it is zero, the object is in equilibrium.

8. 功、能量与功率：动能、势能与效率 | Work, Energy and Power: Kinetic Energy, Potential Energy and Efficiency

功（work）定义为力与沿力的方向移动的距离的乘积，W = Fs cosθ，单位是焦耳（J）。能量是做功的能力，单位也是焦耳。动能（kinetic energy）是物体由于运动而具有的能量，E_k = ½mv²；重力势能（gravitational potential energy）是物体因位置而具有的能量，E_p = mgh。能量守恒定律指出，能量既不能被创造也不能被消灭，只能从一种形式转化为另一种形式。

Work is defined as the product of force and the distance moved in the direction of the force, W = Fs cosθ, measured in joules (J). Energy is the capacity to do work, also measured in joules. Kinetic energy is the energy an object has because of its motion, E_k = ½mv²; gravitational potential energy is the energy an object has because of its position, E_p = mgh. The law of conservation of energy states that energy cannot be created or destroyed, only converted from one form to another.

功率（power）是能量转换或做功的速率，P = W/t，单位是瓦特（W），1 W = 1 J s⁻¹。效率（efficiency）是有用输出能量（或功率）与总输入能量（或功率）之比，通常用百分数表示。效率永远小于或等于 100%，因为总会有能量以热、声等形式耗散掉。

Power is the rate of energy transfer or of doing work, P = W/t, measured in watts (W), where 1 W = 1 J s⁻¹. Efficiency is the ratio of useful output energy (or power) to total input energy (or power), usually expressed as a percentage. Efficiency is always less than or equal to 100%, because some energy is always dissipated as heat, sound or other forms.

9. 波的关键术语：波长、频率、相干性与干涉 | Key Wave Terms: Wavelength, Frequency, Coherence and Interference

波长（wavelength）是相邻两个同相位点（如两个相邻波峰）之间的距离，符号 λ。频率（frequency）是每秒钟通过某点的完整波的个数，单位是赫兹（Hz）。周期（period）是一个完整波通过某点所用的时间，T = 1/f。波速、频率和波长的关系是 v = fλ，这是波动问题中最常用的方程。

Wavelength is the distance between two adjacent points in phase (such as two adjacent crests), symbol λ. Frequency is the number of complete waves passing a point per second, measured in hertz (Hz). Period is the time for one complete wave to pass a point, T = 1/f. The relationship linking wave speed, frequency and wavelength is v = fλ, the most frequently used equation in wave problems.

相干（coherence）指两列波具有恒定的相位差，通常要求它们频率相同。干涉（interference）是两列相干波叠加时形成的稳定增强和减弱图样：波峰相遇处发生相长干涉（constructive interference），波峰与波谷相遇处发生相消干涉（destructive interference）。衍射（diffraction）是波绕过障碍物或通过狭缝时发生扩散的现象，狭缝越窄衍射越明显。

Coherence means two waves have a constant phase difference, which usually requires them to have the same frequency. Interference is the stable pattern of reinforcement and cancellation formed when two coherent waves overlap: where crests meet there is constructive interference, and where a crest meets a trough there is destructive interference. Diffraction is the spreading of waves as they pass around an obstacle or through a gap, and the narrower the gap, the more pronounced the diffraction.

偏振（polarisation）是横波特有的性质：横波的振动方向垂直于传播方向，偏振只允许某一特定方向的振动通过。纵波（如声波）不能偏振。光可以通过偏振片证明它是横波。驻波（standing wave）是两列频率相同、方向相反的波叠加形成的固定图样，波节（node）处振幅为零，波腹（antinode）处振幅最大。

Polarisation is a property unique to transverse waves: in a transverse wave the vibration is perpendicular to the direction of travel, and polarisation allows only vibrations in one particular direction to pass. Longitudinal waves (such as sound) cannot be polarised. Light can be shown to be transverse by passing it through a polarising filter. A standing wave is a fixed pattern formed by the superposition of two waves of equal frequency travelling in opposite directions; nodes are points of zero amplitude and antinodes are points of maximum amplitude.

10. 电学与电路术语：电流、电压、电阻与电动势 | Electricity and Circuit Terms: Current, Voltage, Resistance and EMF

电流（current）是电荷的流动速率，I = Q/t，单位是安培（A），1 A = 1 C s⁻¹。电势差（potential difference，简称 p.d.，也叫电压 voltage）是单位电荷通过元件时转移的能量，单位是伏特（V）。电阻（resistance）是电势差与电流之比，R = V/I，单位是欧姆（Ω）。欧姆定律指出，在温度恒定时，导体的电流与两端电势差成正比。

Current is the rate of flow of charge, I = Q/t, measured in amperes (A), where 1 A = 1 C s⁻¹. Potential difference (p.d., also called voltage) is the energy transferred per unit charge as it passes through a component, measured in volts (V). Resistance is the ratio of potential difference to current, R = V/I, measured in ohms (Ω). Ohm’s law states that, at constant temperature, the current through a conductor is proportional to the potential difference across it.

电动势（electromotive force，简称 e.m.f.）是电源在单位电荷通过时所提供的能量，单位也是伏特，但它描述的是电源本身，而不是电路中的元件。内阻（internal resistance）是电源内部对电流的阻碍，端电压（terminal p.d.）等于电动势减去内阻上的电压降：V = ε − Ir。串联电路中电流处处相等、总电阻为各电阻之和；并联电路中各支路电压相等、总电阻的倒数为各电阻倒数之和。

Electromotive force (e.m.f.) is the energy supplied by a source per unit charge passing through it, also measured in volts, but it describes the source itself rather than a circuit component. Internal resistance is the opposition to current inside the source, and the terminal p.d. equals the e.m.f. minus the voltage dropped across the internal resistance: V = ε − Ir. In a series circuit the current is the same everywhere and the total resistance is the sum of the individual resistances; in a parallel circuit each branch has the same voltage and the reciprocal of the total resistance equals the sum of the reciprocals of the individual resistances.

11. 材料术语：密度、胡克定律与应力应变 | Materials Terms: Density, Hooke’s Law and Stress-Strain

密度（density）是单位体积的质量，ρ = m/V，单位是 kg m⁻³。它是描述材料特性的基本量，不同材料密度不同。胡克定律（Hooke’s law）指出，在弹性限度内，弹簧的伸长量与施加的力成正比，F = kΔL，其中 k 是劲度系数（spring constant），单位是 N m⁻¹。

Density is the mass per unit volume, ρ = m/V, measured in kg m⁻³. It is a basic quantity describing the properties of a material, and different materials have different densities. Hooke’s law states that, within the elastic limit, the extension of a spring is proportional to the applied force, F = kΔL, where k is the spring constant, measured in N m⁻¹.

应力（stress）是单位面积上的力，单位是帕斯卡（Pa）；应变（strain）是伸长量与原长之比，是一个无量纲的比值。杨氏模量（Young modulus）是应力与应变之比，描述材料的刚度，单位也是帕斯卡。弹性形变（elastic deformation）在撤去力后物体恢复原状，塑性形变（plastic deformation）则使物体永久变形，二者以弹性限度（elastic limit）为界。

Stress is the force per unit area, measured in pascals (Pa); strain is the extension divided by the original length, a dimensionless ratio. The Young modulus is the ratio of stress to strain, describing the stiffness of a material, also measured in pascals. Elastic deformation is reversible when the force is removed, while plastic deformation leaves the object permanently changed; the two are separated by the elastic limit.

12. 粒子与量子术语：光子、光电子与功函数 | Particle and Quantum Terms: Photons, Photoelectrons and Work Function

光子（photon）是电磁辐射的量子，能量由 E = hf 给出，其中 h 是普朗克常数，f 是频率。光电效应（photoelectric effect）是光照射金属表面使电子逸出的现象。要使电子逸出，光子能量必须至少等于金属的功函数（work function，符号 φ），这是从金属表面移走一个电子所需的最小能量。

A photon is a quantum of electromagnetic radiation, carrying energy E = hf, where h is the Planck constant and f is the frequency. The photoelectric effect is the emission of electrons from a metal surface when light shines on it. For an electron to escape, the photon energy must be at least equal to the metal’s work function (symbol φ), the minimum energy needed to remove an electron from the surface.

逸出的电子称为光电子（photoelectron）。光电效应方程 E_k(max) = hf − φ 说明，最大动能等于光子能量减去功函数。关键结论是：单个光子的能量只取决于频率，而与光强无关；增大光强只增加每秒到达的光子数，从而增加逸出的电子数，但不会提高每个光电子的动能。

The emitted electrons are called photoelectrons. The photoelectric equation E_k(max) = hf − φ states that the maximum kinetic energy equals the photon energy minus the work function. The crucial conclusion is that the energy of a single photon depends only on its frequency, not on the intensity of the light; increasing the intensity only increases the number of photons arriving per second and hence the number of electrons emitted, without raising the kinetic energy of each photoelectron.

粒子物理中的核心术语还包括核子（nucleon，指质子和中子）、同位素（isotope，质子数相同而中子数不同的原子）和比电荷（specific charge，电荷与质量之比）。这些词在 AQA 的粒子单元中频繁出现，准确使用它们是理解题目和规范答题的基础。

Other core terms in particle physics include nucleon (a proton or neutron), isotope (atoms with the same number of protons but different numbers of neutrons) and specific charge (the ratio of charge to mass). These words appear frequently in the AQA particles unit, and using them accurately is the basis for both understanding the questions and answering them correctly.

Summary | 总结

掌握 AQA AS 物理的学科专用词汇，关键是理解”一词一义”的精确性：速度与速率、位移与距离、准确度与精密度、系统误差与随机误差，这些成对的词必须能清楚区分。基本单位与导出单位、SI 词头、量纲一致性是贯穿所有计算的底层语言；功、能量、功率和电学量纲则把术语与公式一一对应起来。答题时准确使用术语，往往就是保住那关键几分的关键。

The key to mastering AQA AS Physics subject-specific vocabulary is understanding the precision of “one word, one meaning”: velocity versus speed, displacement versus distance, accuracy versus precision, and systematic versus random error must all be clearly distinguished. Base units, derived units, SI prefixes and dimensional homogeneity are the underlying language of every calculation, while work, energy, power and electrical quantities map each term onto its formula. Using terminology accurately when answering questions is often what secures those crucial final marks.

更多咨询请联系16621398022（同微信）