📚 Core Knowledge Review for CIE AS Physics | CIE AS物理核心知识点梳理
CIE AS Physics builds the foundation for understanding the physical world, from subatomic particles to the large-scale behaviour of materials and waves. Mastering the core concepts in Year 12 is essential not only for exam success but also for developing the analytical skills needed in further studies. This article distils the syllabus into eleven key topics, presenting the must-know definitions, formulas, and principles in a clear bilingual format.
CIE AS 物理为理解从亚原子粒子到材料与波的大尺度行为奠定了基础。掌握12年级的核心概念不仅对考试成功至关重要，也有助于培养进阶学习所需的分析能力。本文将考纲浓缩为十一个关键主题，以清晰的中英双语形式呈现必知的定义、公式和原理。
1. Physical Quantities & Units | 物理量与单位
All physical quantities can be expressed in terms of a set of base quantities and their SI units: length (m), mass (kg), time (s), electric current (A), temperature (K), amount of substance (mol), and luminous intensity (cd). Derived units, such as the newton (N) and joule (J), are combinations of these base units.
所有物理量都可以用一组基本量及其国际单位表示：长度(m)、质量(kg)、时间(s)、电流(A)、温度(K)、物质的量(mol)和发光强度(cd)。导出单位，如牛顿(N)和焦耳(J)，是这些基本单位的组合。
Scalars have magnitude only, while vectors have both magnitude and direction. Examples of scalars include mass, speed, and energy; vectors include displacement, velocity, and force. Vector addition must account for direction, either graphically or by resolving into perpendicular components.
标量只有大小，矢量既有大小又有方向。标量的例子有质量、速率和能量；矢量的例子包括位移、速度和力。矢量相加必须考虑方向，可以通过作图法或分解为垂直分量来实现。
Measurements always contain uncertainty; precision reflects the spread of repeated readings, while accuracy describes how close a measurement is to the true value. Prefixes like kilo (10³), milli (10⁻³), and nano (10⁻⁹) should be applied confidently.
测量总是存在不确定性；精密度反映重复读数的离散程度，而准确度描述测量值与真值的接近程度。应熟练使用千(10³)、毫(10⁻³)、纳(10⁻⁹)等词头。
2. Kinematics | 运动学
Kinematics describes motion in terms of displacement, velocity, and acceleration without considering its causes. The slope of a displacement–time graph gives velocity, while the slope of a velocity–time graph gives acceleration; the area under a velocity–time graph represents displacement.
运动学用位移、速度和加速度描述运动而不考虑其成因。位移-时间图的斜率表示速度，速度-时间图的斜率表示加速度；速度-时间图下的面积代表位移。
For uniform acceleration, four equations of motion apply:
v = u + at
对于匀加速运动，适用四个运动方程：
v = u + at
s = ut + ½at²
v² = u² + 2as
s = ½(u + v)t
², with direction usually taken as positive downwards or upwards depending on the coordinate system.
重力作用下的自由落体是特例，加速度 a = g = 9.81 m s⁻²，方向可根据坐标系取向下或向上为正。
3. Dynamics | 动力学
Newton’s three laws of motion form the core of dynamics. The first law defines balanced forces and inertia; the second law, F = ma, relates net force to acceleration; the third law states that forces always occur in equal and opposite action–reaction pairs.
牛顿运动三定律构成动力学的核心。第一定律定义了平衡力和惯性；第二定律 F = ma 将净力与加速度联系起来；第三定律指出力总是以大小相等、方向相反的作用力与反作用力对出现。
force acts. Impulse is the change in momentum: Δp = FΔt = mv − mu. The area under a force–time graph gives the impulse.
动量 p = mv 在没有合外力的情况下在所有碰撞和爆炸中守恒。冲量是动量的变化量：Δp = FΔt = mv − mu。力-时间图下的面积即为冲量。
Types of collisions can be classified as perfectly elastic (kinetic energy conserved), inelastic (some kinetic energy lost), or completely inelastic (objects stick together).
碰撞类型可分为完全弹性（动能守恒）、非弹性（部分动能损失）或完全非弹性（物体粘在一起）。
4. Forces, Density & Pressure | 力、密度与压强
The moment of a force about a point is the product of the force and the perpendicular distance: M = Fd. An object is in equilibrium when the resultant force is zero and the resultant moment about any point is zero; this principle is used to solve problems involving beams and levers.
力对一点的力矩等于力与垂直距离的乘积：M = Fd。当合外力为零且对任一点的合力矩为零时，物体处于平衡状态；此原理常用于解决横梁和杠杆问题。
/V is a characteristic property of a material. Pressure is defined as force per unit area: p = F/A. In fluids, pressure increases with depth: p = ρgh. Archimedes' principle states that the upthrust equals the weight of fluid displaced.
密度 ρ = m/V 是材料的一种特性。压强定义为单位面积上的力：p = F/A。在流体中，压强随深度增加：p = ρgh。阿基米德原理指出，浮力等于排开流体的重量。
Centre of gravity is the point where the entire weight of an object may be considered to act. For a uniform lamina, it is at the geometrical centre.
重心是物体全部重量可以被视为集中的点。对于均匀薄板，重心位于几何中心。
5. Work, Energy & Power | 功、能与功率
is W = Fs cosθ, where θ is the angle between the force and displacement. Kinetic energy is KE = ½mv² and gravitational potential energy is GPE = mgh. The work–energy principle states that net work equals change in kinetic energy.
恒力做的功为 W = Fs cosθ，其中 θ 为力与位移的夹角。动能为 KE = ½mv²，重力势能为 GPE = mgh。功能原理指出，净功等于动能的变化量。
Power is the rate of doing work: P = W/t. For a constant force moving at velocity v, the instantaneous power is P = Fv. Efficiency is the ratio of useful output energy to total input energy.
功率是做功的快慢：P = W/t。对于以速度 v 运动的恒力，瞬时功率为 P = Fv。效率为有用输出能量与总输入能量之比。
Energy is always conserved, transforming between forms such as kinetic, potential, thermal, and internal energy.
能量总是守恒的，可以在动能、势能、热能和内能等形式之间转化。
6. Deformation of Solids | 固体的变形
Hooke's law states that the extension x of a spring or wire is directly proportional to the applied force, provided the elastic limit is not exceeded: F = kx. The spring constant k is a measure of stiffness.
胡克定律指出，只要不超过弹性极限，弹簧或金属丝的伸长量 x 与外力成正比：F = kx。弹簧常数 k 是刚度的量度。
Stress σ is defined as force per unit cross‑sectional area: σ = F/A. Strain ε is the fractional extension: ε = ΔL/L. Young modulus E measures the stiffness of a material: E = σ/ε.
应力 σ 定义为单位横截面积上的力：σ = F/A。应变 ε 是伸长分数：ε = ΔL/L。杨氏模量 E 衡量材料的刚度：E = σ/ε。
Stress–strain graphs reveal important points: the limit of proportionality, elastic limit, yield point, and ultimate tensile stress. Ductile and brittle materials show distinct behaviours.
应力-应变图能显示重要节点：比例极限、弹性极限、屈服点和极限拉伸应力。延性材料和脆性材料表现出截然不同的行为。
7. Waves | 波
Waves transfer energy without net movement of matter. In transverse waves, particle oscillation is perpendicular to energy propagation (e.g. electromagnetic waves); in longitudinal waves, oscillation is parallel (e.g. sound). The wave equation links speed, frequency, and wavelength: v = fλ.
波传递能量而不引起物质的净位移。横波中质点振动垂直于能量传播方向（如电磁波）；纵波中振动平行于传播方向（如声波）。波动方程联系波速、频率和波长：v = fλ。
asing frequency, includes radio waves, microwaves, infrared, visible light, ultraviolet, X‑rays, and gamma rays. All travel at speed c = 3.00×10⁸ m s⁻¹ in vacuum.
电磁波谱按频率递增依次为无线电波、微波、红外线、可见光、紫外线、X射线和伽马射线。它们在真空中均以 c = 3.00×10⁸ m s⁻¹ 的速度传播。
Polarisation is evidence that a wave is transverse; only transverse waves can be polarised. A polarising filter transmits only the component oscillating in one plane.
偏振是横波的证据；只有横波才能被偏振。偏振片只允许在某一平面内振动的分量通过。
8. Superposition | 波的叠加
The principle of superposition states that when two or more waves meet, the resultant displacement is the vector sum of the individual displacements. This leads to constructive and destructive interference.
叠加原理指出，当两列或多列波相遇时，合位移是各列位移的矢量和，这会产生相长干涉和相消干涉。
In Young's double‑slit experiment, fringe spacing is given by Δx = λD/a, where D is the slit‑to‑screen distance and a is the slit separation. For a diffraction grating, maxima satisfy d sinθ = nλ, allowing precise wavelength measurements.
在杨氏双缝实验中，条纹间距由 Δx = λD/a 给出，其中 D 为缝屏距，a 为双缝间距。对于衍射光栅，极大遵循 d sinθ = nλ，可用于精确测量波长。
Stationary (standing) waves form when two identical waves travel in opposite directions. Nodes (zero displacement) and antinodes (maximum displacement) are produced. Harmonics in strings and pipes are described by appropriate wavelength‑length relationships.
驻波由两列相同的波沿相反方向传播时形成，产生波节（位移为零）和波腹（位移最大）。弦和管中的谐波由相应的波长-长度关系描述。
9. Electricity | 电学
ference V = W/Q is the energy transferred per unit charge. The volt is equivalent to JC⁻¹.
电流 I = Q/t 是电荷流动的速率。约定电流方向为正电荷流动方向。电势差 V = W/Q 是单位电荷传递的能量。伏特等于 JC⁻¹。
Ohm's law states that the current through a conductor is proportional to the potential difference at constant temperature: V = IR. Resistance depends on material and geometry: R = ρL/A, where ρ is resistivity.
欧姆定律指出，在恒定温度下，通过导体的电流与电势差成正比：V = IR。电阻取决于材料和几何形状：R = ρL/A，其中 ρ 为电阻率。
Electrical power is given by P = VI = I²R = V²/R. The kilowatt‑hour (kW h) is a unit of energy used in electricity consumption.
电功率由 P = VI = I²R = V²/R 给出。千瓦时 (kW h) 是耗电量的能量单位。
10. D.C. Circuits | 直流电路
Kirchhoff's first law states that the total current entering a junction equals the total current leaving it (charge conservation). His second law states that the sum of the e.m.f.s in any closed loop equals the sum of the p.d.s (energy conservation).
基尔霍夫第一定律指出，流入节点的总电流等于流出节点的总电流（电荷守恒）。第二定律指出，任一闭合回路中电动势之和等于电压降之和（能量守恒）。
In series circuits, current is the same everywhere and voltages add; total resistance is Rtotal = R₁ + R₂ + R₃ + …. In parallel circuits, voltage is the same across each branch and currents add; total resistance follows 1/Rtotal = 1/R₁ + 1/R₂ + ….
串联电路中电流处处相等，电压相加；总电阻为 Rtotal = R₁ + R₂ + R₃ + …。并联电路中各支路电压相等，电流相加；总电阻遵循 1/Rtotal = 1/R₁ + 1/R₂ + …。
A real cell has internal resistance r, reducing the terminal p.d.: V = E − Ir, where E is the electromotive force. A potential divider circuit uses two resistors to obtain a variable output voltage.
实际电源有内阻 r，使端电压降低：V = E − Ir，其中 E 为电动势。电位器电路使用两个电阻获得可调输出电压。
11. Particle Physics | 粒子物理
Atoms consist of a nucleus containing protons and neutrons, surrounded by electrons. Nuclear symbols are written as ᴆX, where Z is the proton number and A the nucleon number. Isotopes share the same Z but differ in A.
原子由包含质子和中子的原子核以及绕核电子组成。核素符号写作 ᴆX，Z 为质子数，A 为核子数。同位素质子数相同而核子数不同。
The Standard Model classifies particles into hadrons (made of quarks) and leptons (fundamental). Baryons, such as protons (uud) and neutrons (udd), are composed of three quarks. Mesons consist of a quark–antiquark pair. Leptons include electrons and neutrinos.
标准模型将粒子分为强子（由夸克组成）和轻子（基本粒子）。重子如质子(uud)和中子(udd)由三个夸克构成。介子由夸克-反夸克对组成。轻子包括电子和中微子。
In beta‑ neutron transforms into a proton, emitting an electron and an antineutrino: n → p + e⁻ + ν̅ vation of charge, baryon number, and lepton number is obeyed. Quark change: d → u + e⁻ + ν̅ₑ.
在β⁻衰变中，中子转变为质子，并发射一个电子和一个反中微子：n → p + e⁻ + ν̅ₑ。该过程满足电荷、重子数和轻子数守恒。夸克变化：d → u + e⁻ + ν̅ₑ。
posite charge and other quantum numbers. Annihilation and pair production demonstrate mass–energy equivalence E = mc².
反粒子与其对应粒子质量相同，但电荷等量子数相反。湮灭和粒子对的产生体现了质能等价 E = mc²。
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