📚 Year 12 CIE Physics: Quick Guide to Key Terms | CIE物理Year 12核心术语速记指南
Mastering the terminology is the first step towards acing CIE AS-Level Physics. This guide provides quick definitions and memory aids for essential terms across the Year 12 syllabus. Each term is paired with a Chinese explanation to help you build a solid bilingual understanding. Let’s turn confusing jargon into easy marks.
掌握术语是攻克CIE AS物理的第一步。本指南为Year 12教学大纲中的核心术语提供快速定义与记忆技巧，每个术语均配有中文释义，帮助你建立扎实的双语理解。让令人困惑的术语变成你的轻松拿分点。
1. Physical Quantities and Units | 物理量与单位
Base quantity: A fundamental physical quantity that is defined independently, such as length, mass, time, electric current, thermodynamic temperature, amount of substance, and luminous intensity. All other quantities are derived from these seven.
基本量：独立定义的基本物理量，例如长度、质量、时间、电流、热力学温度、物质的量和发光强度。所有其他量均由这七个量导出。
Derived quantity: A physical quantity expressed in terms of base quantities through multiplication or division. Example: speed = length / time.
导出量：通过基本量相乘或相除表达的物理量。例如：速度 = 长度 / 时间。
SI prefixes: Standard multiples and submultiples used to avoid writing very large or small numbers. Common examples: kilo (k, 10³), mega (M, 10⁶), giga (G, 10⁹), centi (c, 10⁻²), milli (m, 10⁻³), micro (μ, 10⁻⁶), nano (n, 10⁻⁹), pico (p, 10⁻¹²).
SI词头：避免书写极大或极小数字的标准倍数和分数。常见例子：千(k,10³)、兆(M,10⁶)、吉(G,10⁹)、厘(c,10⁻²)、毫(m,10⁻³)、微(μ,10⁻⁶)、纳(n,10⁻⁹)、皮(p,10⁻¹²)。
Homogeneous equation: An equation in which the base units on both sides are the same. This is the basis of checking formula consistency using dimensional analysis.
齐次方程：方程两边基本单位相同的方程。这是利用量纲分析检验公式一致性的基础。
2. Scalars and Vectors | 标量与矢量
Scalar: A quantity that has magnitude only. Examples: mass, temperature, speed, energy, distance.
标量：只有大小的量。例如：质量、温度、速率、能量、距离。
Vector: A quantity that has both magnitude and direction. Examples: displacement, velocity, acceleration, force, momentum.
矢量：既有大小又有方向的量。例如：位移、速度、加速度、力、动量。
Resultant vector: A single vector that produces the same effect as two or more vectors acting together. It is obtained by vector addition, often using the tip-to-tail method or perpendicular components.
合矢量：与两个或多个矢量共同作用产生相同效果的单个矢量。通过矢量加法获得，常用三角形法或垂直分量法。
Resolving a vector: Splitting a vector into two perpendicular components, typically horizontal and vertical. If a force F makes an angle θ with the horizontal, the horizontal component is F cos θ and the vertical component is F sin θ.
分解矢量：将一个矢量分解为两个垂直分量，通常是水平和垂直方向。如果一个力F与水平方向夹角为θ，则水平分量为F cos θ，垂直分量为F sin θ。
3. Kinematics Terms | 运动学术语
Displacement: The distance moved in a particular direction; a vector quantity measured from the initial position to the final position.
位移：在特定方向上的移动距离；是从初位置指向末位置的矢量。
Velocity: The rate of change of displacement. It is a vector. Instantaneous velocity is the gradient of a displacement–time graph.
速度：位移的变化率。是矢量。瞬时速度是位移-时间图上的切线斜率。
Acceleration: The rate of change of velocity. Constant acceleration is assumed in the SUVAT equations. On a velocity–time graph, acceleration is the gradient and displacement is the area under the graph.
加速度：速度的变化率。SUVAT方程假设加速度恒定。在速度-时间图中，加速度为斜率，位移为图下面积。
Free fall: Motion under the influence of gravity alone, where the acceleration is the acceleration of free fall g (approx 9.81 m s⁻² on Earth). In free fall, air resistance is neglected.
自由落体：仅在重力作用下的运动，加速度为自由落体加速度g（地球上约9.81 m s⁻²）。自由落体忽略空气阻力。
4. Dynamics: Forces and Newton’s Laws | 动力学：力与牛顿定律
Newton’s first law: An object will remain at rest or in uniform motion in a straight line unless acted upon by a resultant external force. This introduces the concept of inertia.
牛顿第一定律：除非受到合外力作用，否则物体将保持静止或匀速直线运动状态。这引入了惯性的概念。
Newton’s second law: The resultant force on an object is equal to the rate of change of its momentum. For constant mass, this simplifies to F = ma.
牛顿第二定律：物体所受的合力等于其动量的变化率。对于质量不变的情况，简化为F = ma。
Newton’s third law: If body A exerts a force on body B, then body B exerts an equal but opposite force on body A. The two forces are of the same type and act on different bodies.
牛顿第三定律：若物体A对物体B施加一个力，则物体B同时对物体A施加一个大小相等、方向相反的力。这两个力属于同种性质的力，作用在不同物体上。
Mass vs Weight: Mass is a scalar measuring the amount of matter in an object (unit: kg). Weight is the gravitational force acting on the mass (W = mg) and is a vector (unit: N).
质量与重量：质量是标量，衡量物体所含物质的多少（单位：kg）。重量是作用在质量上的引力（W = mg），是矢量（单位：N）。
5. Momentum and Impulse | 动量与冲量
Momentum: The product of an object’s mass and velocity (p = mv). It is a vector quantity with unit kg m s⁻¹ or N s.
动量：物体质量与速度的乘积(p = mv)。是矢量，单位为kg m s⁻¹ 或 N s。
Impulse: The product of a force and the time for which it acts (impulse = FΔt). Impulse equals the change in momentum (FΔt = Δp). The area under a force–time graph gives the impulse.
冲量：力与其作用时间的乘积(冲量 = FΔt)。冲量等于动量的变化(FΔt = Δp)。力-时间图下的面积即冲量。
Principle of conservation of momentum: In a closed system with no external forces, the total momentum before a collision or explosion is equal to the total momentum after. This applies to both elastic and inelastic collisions.
动量守恒定律：在没有外力的封闭系统中，碰撞或爆炸前的总动量等于碰撞或爆炸后的总动量。这适用于弹性碰撞和非弹性碰撞。
Elastic collision: A collision in which both momentum and total kinetic energy are conserved. In reality, collisions between atomic particles can be nearly perfectly elastic.
弹性碰撞：动量和总动能均守恒的碰撞。实际上，原子粒子之间的碰撞可以近乎完全弹性。
6. Energy, Work, Power and Efficiency | 能量、功、功率与效率
Work done: The product of a force and the displacement in the direction of the force (W = Fs cos θ). Work is a scalar measured in joules (J). When the force is at an angle to the displacement, only the parallel component does work.
功：力与沿该力方向位移的乘积(W = Fs cos θ)。功是标量，单位为焦耳(J)。当力与位移存在夹角时，只有平行分量做功。
Kinetic energy: The energy possessed by an object due to its motion, given by KE = ½ mv². This is derived from the work-energy theorem.
动能：物体因运动而拥有的能量，KE = ½ mv²。源自动能定理。
Gravitational potential energy: The energy stored in an object due to its position in a gravitational field. Near Earth’s surface, ΔGPE = mgΔh, where h is the height change.
重力势能：物体因其在引力场中的位置而储存的能量。在地球表面附近，ΔGPE = mgΔh，其中h为高度变化。
Power: The rate of doing work or transferring energy. P = W / t or P = Fv for constant force and velocity parallel. Unit: watt (W), which equals J s⁻¹.
功率：做功或能量转移的速率。P = W / t，或当力与速度平行且不变时P = Fv。单位：瓦特(W)，即J s⁻¹。
Efficiency: The ratio of useful output power (or energy) to total input power (or energy). Efficiency = (useful output / total input) × 100%. It is always less than 100% due to energy dissipation.
效率：有用输出功率（或能量）与总输入功率（或能量）之比。效率 = (有用输出 / 总输入) × 100%。因能量耗散，效率始终低于100%。
7. Materials: Stress, Strain and Young Modulus | 材料：应力、应变与杨氏模量
Density: Mass per unit volume, ρ = m / V. Usually measured in kg m⁻³.
密度：单位体积的质量，ρ = m / V。常用单位kg m⁻³。
Stress: The force applied per unit cross-sectional area (σ = F / A). Tensile stress stretches; compressive stress squashes. Unit: Pa or N m⁻².
应力：单位横截面积上所施加的力(σ = F / A)。拉伸应力使材料拉伸；压缩应力使材料压缩。单位：Pa 或 N m⁻²。
Strain: The fractional extension produced, defined as extension divided by original length (ε = ΔL / L₀). Strain is a ratio with no unit.
应变：产生的相对伸长，定义为伸长量除以原长(ε = ΔL / L₀)。应变是比值，无单位。
Young modulus: A measure of the stiffness of a material, given by E = stress / strain for the linear elastic region. Its unit is Pa. A high Young modulus means the material is stiff.
杨氏模量：衡量材料刚度的量，在弹性线性区内E = 应力 / 应变。单位为Pa。杨氏模量高意味着材料刚度大。
Elastic limit: The maximum stress a material can withstand and still return to its original shape when the load is removed. Beyond this point, plastic deformation occurs.
弹性极限：材料能承受且卸载后仍能恢复原状的最大应力。超过此点，发生塑性变形。
8. Waves: Basic Properties | 波：基本性质
Amplitude: The maximum displacement of a particle from its equilibrium position. In a transverse wave, it is the height of a crest or depth of a trough.
振幅：质点离开平衡位置的最大位移。在横波中，是波峰的高度或波谷的深度。
Wavelength: The distance between two consecutive points that are in phase, e.g., crest to crest or compression to compression. Symbol: λ.
波长：两相邻同相位点之间的距离，如波峰到波峰或密部到密部。符号：λ。
Frequency: The number of complete wave cycles passing a point per unit time. Unit: hertz (Hz). f = 1/T, where T is the period.
频率：单位时间内通过某点的完整波周期数。单位：赫兹(Hz)。f = 1/T，T为周期。
Wave speed: The speed at which energy is transferred by the wave. v = f λ. For electromagnetic waves in a vacuum, v = c ≈ 3.00 × 10⁸ m s⁻¹.
波速：波传递能量的速度。v = f λ。对于真空中的电磁波，v = c ≈ 3.00 × 10⁸ m s⁻¹。
Transverse vs Longitudinal: In transverse waves, particle vibration is perpendicular to wave travel (e.g., light, water ripples). In longitudinal waves, vibration is parallel to travel (e.g., sound, P-waves).
横波与纵波：横波中质点的振动方向垂直于波的传播方向（如光、水波）。纵波中振动方向平行于传播方向（如声波、P波）。
9. Wave Superposition and Interference | 波的叠加与干涉
Principle of superposition: When two or more waves meet at a point, the resultant displacement is the vector sum of the individual displacements.
叠加原理：当两个或多个波在一点相遇时，合位移是各波独自位移的矢量和。
Constructive interference: Occurs when waves arrive in phase (path difference = nλ, where n is an integer). The amplitudes add to produce a wave of larger amplitude.
相长干涉：当波同相到达时发生（波程差 = nλ，n为整数）。振幅相加，产生更大振幅的波。
Destructive interference: Occurs when waves arrive exactly out of phase (path difference = (n + ½)λ). The amplitudes cancel, giving a minimum.
相消干涉：当波完全反相到达时发生（波程差 = (n + ½)λ）。振幅相消，得到最小值。
Stationary wave: A wave pattern formed when two progressive waves of equal frequency and amplitude travel in opposite directions. Nodes are points of zero displacement; antinodes are points of maximum displacement.
驻波：两个频率和振幅相同但传播方向相反的进行波叠加形成的波形。波节是位移为零的点；波腹是位移最大的点。
Diffraction: The spreading of a wave when it passes through a gap or around an obstacle. The effect is most significant when the gap width is comparable to the wavelength.
衍射：波通过狭缝或绕过障碍物时发生的扩散现象。当缝宽与波长相近时，衍射效应最显著。
10. Electric Current and Charge | 电流与电荷
Electric current: The rate of flow of electric charge. I = ΔQ / Δt. Conventionally, the direction of current is the direction of positive charge flow. In metals, electrons move opposite to conventional current.
电流：电荷流动的速率。I = ΔQ / Δt。传统上，电流方向为正电荷流动方向。在金属中，电子运动方向与常规电流方向相反。
Potential difference (p.d.): The energy transferred per unit charge when charge moves between two points in a circuit. V = W / Q. Measured in volts (V), where 1 V = 1 J C⁻¹.
电势差：电荷在电路中两点间移动时，每单位电荷转换的能量。V = W / Q。单位为伏特(V)，1 V = 1 J C⁻¹。
Resistance: The opposition to current flow, defined as R = V / I for a component. Unit: ohm (Ω). The resistance of a conductor depends on length, cross-sectional area and resistivity: R = ρL / A.
电阻：对电流的阻碍作用，对某个元件定义为R = V / I。单位：欧姆(Ω)。导体的电阻取决于长度、横截面积和电阻率：R = ρL / A。
Ohm’s law: For a metallic conductor at constant temperature, the current through it is directly proportional to the potential difference across it, provided physical conditions remain constant. Ohmic conductors obey V ∝ I.
欧姆定律：对于温度恒定的金属导体，在物理条件不变时，通过它的电流与两端电势差成正比。欧姆导体满足V ∝ I。
11. DC Circuits and Kirchhoff’s Laws | 直流电路与基尔霍夫定律
Electromotive force (e.m.f.): The energy supplied by a source per unit charge passing through it. It is measured in volts and is not a force. E.m.f. drives charge around a complete circuit.
电动势：电源每单位电荷通过它所提供的能量。单位伏特，不是力。电动势驱动电荷环绕完整回路。
Internal resistance (r): The resistance within a source of e.m.f. that causes some energy to be dissipated as heat. Terminal potential difference V = ε − Ir, where ε is the e.m.f. and I is the current.
内阻(r)：电源内部的电阻，使部分能量以热的形式耗散。端电压V = ε − Ir，其中ε为电动势，I为电流。
Kirchhoff’s first law: The sum of currents entering a junction equals the sum of currents leaving it. This is a statement of conservation of charge. ΣIᵢₙ = ΣIₒᵤₜ.
基尔霍夫第一定律：流入节点的电流之和等于流出节点的电流之和。这是电荷守恒的体现。ΣI入 = ΣI出。
Kirchhoff’s second law: In any closed loop of a circuit, the sum of the e.m.f.s equals the sum of the p.d.s across the components. This follows from conservation of energy. Σε = ΣIR.
基尔霍夫第二定律：在电路的任何闭合回路中，电动势之和等于各元件上电势差之和。源于能量守恒。Σε = ΣIR。
Potential divider: An arrangement of resistors used to obtain a fraction of the input potential difference. For two resistors R₁ and R₂ in series, Vₒᵤₜ = Vᵢₙ × [R₂ / (R₁+R₂)].
分压器：利用电阻器获得输入电势差一部分的装置。对于串联的R₁和R₂，V输出 = V输入 × [R₂/(R₁+R₂)]。
12. Particle and Nuclear Physics | 粒子与核物理
Nuclide notation: A symbolic representation of a nucleus: ᴬZ X, where A is the mass number (protons + neutrons), Z is the atomic number (protons). Isotopes have the same Z but different A.
核素符号：原子核的符号表示：ᴬZ X，A为质量数（质子+中子），Z为原子序数（质子数）。同位素的Z相同而A不同。
Alpha particle: A helium nucleus, ⁴₂He or α, consisting of two protons and two neutrons. It is highly ionising but has low penetration; stopped by paper.
α粒子：氦原子核，⁴₂He 或 α，包含两个质子和两个中子。电离能力强但穿透力弱，可被纸阻挡。
Beta particle: A fast-moving electron (β⁻) or positron (β⁺) emitted from an unstable nucleus. β⁻ decay involves a neutron turning into a proton, with emission of an electron and an antineutrino. β⁻ particles have moderate ionising ability and are stopped by a few mm of aluminium.
β粒子：从不稳定核中发射出的快速电子(β⁻)或正电子(β⁺)。β⁻衰变中一个中子转变成质子，同时发射一个电子和一个反中微子。β⁻粒子的电离能力中等，可被几毫米铝阻挡。
Gamma radiation: High-energy electromagnetic radiation emitted from an excited nucleus. It has no mass or charge, very high penetration, and is stopped only by thick lead or concrete.
γ辐射：从激发态原子核发射的高能电磁辐射。无质量、无电荷，穿透力极强，只能被厚铅板或混凝土阻挡。
Activity: The rate of decay of a radioactive source, measured in becquerels (Bq), where 1 Bq = 1 decay per second. Activity A = λN, where λ is the decay constant.
活度：放射源的衰变速率，单位贝克勒尔(Bq)，1 Bq = 每秒钟衰变一次。活度 A = λN，λ为衰变常数。
Half-life: The time taken for the activity of a radioactive source (or the number of undecayed nuclei) to reduce to half its initial value. It is constant for a given isotope.
半衰期：放射源的活度（或未衰变原子核数量）减少到初始值一半所需的时间。对于给定同位素，半衰期是常量。
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