📚 AS Physics Core Concepts Revision Guide | AS 物理核心概念复习指南
Welcome to this comprehensive revision guide for AS Physics. This guide covers the essential topics that appear most frequently in exam papers, helping you master the core concepts, key equations, and problem-solving techniques needed for success at the AS level.
欢迎阅读这份 AS 物理综合复习指南。本指南涵盖考试中最常出现的关键主题，帮助你掌握核心概念、重要方程和解题技巧，为 AS 阶段的学习与考试奠定坚实基础。
1. Physical Quantities and Units | 物理量与单位
Physics is the science of measurement. Every physical quantity consists of a numerical value and a unit. The International System (SI) defines seven base quantities: mass (kg), length (m), time (s), electric current (A), temperature (K), amount of substance (mol), and luminous intensity (cd).
物理学是一门测量的科学。每个物理量都由数值和单位组成。国际单位制（SI）定义了七个基本量：质量（kg）、长度（m）、时间（s）、电流（A）、温度（K）、物质的量（mol）和发光强度（cd）。
Derived quantities are formed by combining base units. For example, velocity is measured in m s⁻¹, acceleration in m s⁻², and force in kg m s⁻², which is called the newton (N). You should be able to express derived units in terms of base units, as this skill is commonly tested in exams.
导出量由基本单位组合而成。例如，速度的单位为 m s⁻¹，加速度的单位为 m s⁻²，力的单位为 kg m s⁻²，称为牛顿（N）。你应该能够用基本单位表示导出单位，这是考试中常见的考查技能。
| Derived Quantity | Unit Name | Base Units |
| Force (力) | newton (N) | kg m s⁻² |
| Energy (能量) | joule (J) | kg m² s⁻² |
| Power (功率) | watt (W) | kg m² s⁻³ |
| Pressure (压强) | pascal (Pa) | kg m⁻¹ s⁻² |
| Charge (电荷) | coulomb (C) | A s |
Prefixes are essential for handling very large and very small quantities. Common prefixes include kilo (k, 10³), centi (c, 10⁻²), milli (m, 10⁻³), micro (μ, 10⁻⁶), nano (n, 10⁻⁹), and pico (p, 10⁻¹²). Always convert to base or standard units before substituting values into equations.
前缀在处理极大和极小的量时至关重要。常见前缀包括千（k，10³）、厘（c，10⁻²）、毫（m，10⁻³）、微（μ，10⁻⁶）、纳（n，10⁻⁹）和皮（p，10⁻¹²）。在将数值代入方程之前，务必先将其转换为基本单位或标准单位。
2. Kinematics: Describing Motion | 运动学：描述运动
Kinematics describes motion without considering its causes. The key quantities are displacement (s), velocity (v), and acceleration (a). Displacement is a vector quantity measuring the distance travelled in a specified direction, while speed is its scalar counterpart. Acceleration is the rate of change of velocity.
运动学描述运动而不考虑其成因。关键物理量为位移（s）、速度（v）和加速度（a）。位移是矢量，衡量沿指定方向移动的距离，而速率是其标量对应量。加速度是速度的变化率。
For motion with constant (uniform) acceleration, the following SUVAT equations apply. Here, u is the initial velocity, v the final velocity, a the acceleration, t the time taken, and s the displacement.
对于匀加速运动，以下 SUVAT 方程适用。其中 u 为初速度，v 为末速度，a 为加速度，t 为经过的时间，s 为位移。
v = u + at
s = ½(u + v)t
v² = u² + 2as
s = ut + ½at²
These four equations allow you to solve any uniform-acceleration problem provided you know three of the five variables. A useful tip is to list what you know and what you need before selecting the appropriate equation.
这四个方程使你在已知五个变量中的任意三个时，能够解出任何匀加速运动问题。一个实用的技巧是，先列出已知量和待求量，再选择恰当的方程。
Velocity-time graphs are particularly powerful: the gradient of the graph represents acceleration, and the area under the graph represents displacement. For an acceleration-time graph, the area under the curve represents the change in velocity.
速度-时间图像尤其强大：图像的斜率代表加速度，图像下方的面积代表位移。对于加速度-时间图像，曲线下方的面积代表速度的变化量。
When an object is projected vertically upward, it experiences a constant downward acceleration due to gravity, g ≈ 9.81 m s⁻². At the highest point, the velocity is momentarily zero, but the acceleration remains 9.81 m s⁻² downward throughout the flight.
当物体竖直上抛时，它受到向下的恒定重力加速度 g ≈ 9.81 m s⁻²。在最高点，速度瞬时为零，但整个飞行过程中加速度始终为 9.81 m s⁻² 向下。
3. Dynamics: Newton’s Laws of Motion | 动力学：牛顿运动定律
Dynamics explains why objects move by linking forces to motion. Newton’s first law states that a body remains at rest or in uniform motion in a straight line unless acted upon by a net external force. This principle of inertia underlies all of mechanics.
动力学通过将力与运动联系起来，解释物体为何运动。牛顿第一定律指出，除非受到合外力作用，物体将保持静止或沿直线做匀速运动。这一惯性原理是整个力学的基础。
Newton’s second law quantifies this relationship: the net force acting on an object equals the product of its mass and its acceleration. Since acceleration is a vector, this equation also determines the direction of the resulting motion.
牛顿第二定律将这一关系量化：物体所受的合外力等于其质量与加速度的乘积。由于加速度是矢量，该方程同时决定了物体运动的方向。
F = ma
Weight is a special case of this law: W = mg, where g ≈ 9.81 m s⁻² on the Earth’s surface. Mass is a measure of the amount of matter and is constant, whereas weight is a force that depends on the local gravitational field strength.
重力是这一定律的特例：W = mg，其中地球表面的 g ≈ 9.81 m s⁻²。质量是物质数量的度量，是恒定的；而重力是一种力，取决于当地的重力场强度。
Newton’s third law states that when two objects interact, they exert equal and opposite forces on each other. These action-reaction pairs act on different bodies, so they never cancel each other out. A common mistake is to confuse an action-reaction pair with balanced forces on the same object.
牛顿第三定律指出，两个物体相互作用时，彼此施加大小相等、方向相反的力。这些作用力与反作用力对作用于不同物体，因此永远不会相互抵消。常见的错误是将作用力与反作用力对与作用在同一物体上的平衡力混淆。
When solving problems, draw a free-body diagram showing all forces acting on the chosen object, resolve forces into perpendicular components if necessary, and then apply F = ma along each axis.
解题时，画出受力分析图，标出所选物体受到的所有力；必要时将力分解为互相垂直的分量，然后沿每个轴应用 F = ma。
4. Work, Energy and Power | 功、能量与功率
Work is done when a force moves an object through a displacement. The equation for work is W = Fs cos θ, where F is the force, s is the displacement, and θ is the angle between the force and the direction of motion. Work is a scalar quantity measured in joules.
当力使物体发生位移时，力就做了功。功的计算公式为 W = Fs cos θ，其中 F 为力，s 为位移，θ 为力与运动方向之间的夹角。功是标量，单位为焦耳。
Kinetic energy is the energy an object possesses due to its motion. Gravitational potential energy is the energy stored due to an object’s position in a gravitational field, given by ΔEₚ = mgΔh.
动能是物体因运动而具有的能量。重力势能是物体因在重力场中的位置而储存的能量，计算公式为 ΔEₚ = mgΔh。
Eₖ = ½mv²
ΔEₚ = mgΔh
The principle of conservation of energy states that energy cannot be created or destroyed, only transformed from one form to another. In a closed system, the total energy remains constant. For example, a ball dropped from a height converts gravitational potential energy into kinetic energy, ignoring air resistance.
能量守恒原理指出，能量既不能凭空产生，也不能凭空消失，只能从一种形式转化为另一种形式。在封闭系统中，总能量保持不变。例如，忽略空气阻力时，从一定高度释放的球将重力势能转化为动能。
Power is the rate at which work is done or energy is transferred. It is measured in watts, where 1 W = 1 J s⁻¹. For an object moving at constant velocity v under a driving force F, the power is given by P = Fv.
功率是做功或能量转移的速率，单位为瓦特，其中 1 W = 1 J s⁻¹。当物体在驱动力 F 作用下以恒定速度 v 运动时，功率由 P = Fv 给出。
P = W / t = Fv
Efficiency is the ratio of useful output energy (or power) to total input energy (or power), usually expressed as a percentage. Exam questions often require you to calculate efficiency and identify energy losses, such as thermal energy due to friction.
效率是有用输出能量（或功率）与总输入能量（或功率）之比，通常以百分比表示。考试题目经常要求你计算效率并识别能量损失，例如因摩擦产生的热能。
5. Deformation of Solids | 固体的形变
When a force is applied to a solid, it may deform. Hooke’s law states that, for a material within its elastic limit, the extension is directly proportional to the applied force. The spring constant k describes the stiffness of the material or spring.
当力作用于固体时，固体可能发生形变。胡克定律指出，在弹性极限内，材料的伸长量与施加的力成正比。劲度系数 k 描述材料或弹簧的刚度。
F = kx
The elastic limit is the maximum force for which the material returns to its original shape when the force is removed. Beyond this point, the material undergoes plastic deformation and a permanent extension remains.
弹性极限是撤去力后材料能够恢复原状的最大力值。超过此极限，材料将发生塑性形变，留下永久伸长。
Tensile stress is defined as the force per unit cross-sectional area, while tensile strain is the extension per unit original length. The Young modulus is the ratio of stress to strain and measures the stiffness of a material. Its unit is pascal (Pa), which is equivalent to N m⁻².
张应力定义为每单位横截面积所受的力，而张应变是每单位原始长度的伸长量。杨氏模量是应力与应变之比，衡量材料的刚度，单位为帕斯卡（Pa），即 N m⁻²。
σ = F / A
ε = x / L
E = σ / ε = FL / (Ax)
The energy stored in a deformed spring is given by the area under the force-extension graph. This stored elastic potential energy is E = ½kx². For a material obeying Hooke’s law, the area is a triangle, giving this simple result.
弹簧形变时储存的能量等于力-伸长图像下的面积。这种储存的弹性势能为 E = ½kx²。对于遵循胡克定律的材料，图像为三角形，因此得到这个简洁的结果。
6. Waves: Fundamentals | 波：基础概念
A wave is a means of transferring energy from one point to another without transferring matter. Waves may be transverse, where particles oscillate perpendicular to the direction of energy transfer, or longitudinal, where particles oscillate parallel to the direction of energy transfer.
波是一种将能量从一点传递到另一点而不传递物质的方式。波可以是横波——质点垂直于能量传递方向振动，也可以是纵波——质点平行于能量传递方向振动。
Key wave properties include wavelength λ, frequency f, and wave speed v. These are related by the wave equation v = fλ. The frequency is measured in hertz (Hz), where 1 Hz = 1 s⁻¹.
波的关键属性包括波长 λ、频率 f 和波速 v。它们通过波动方程 v = fλ 相联系。频率单位为赫兹（Hz），其中 1 Hz = 1 s⁻¹。
v = fλ
Intensity is the power transferred per unit area perpendicular to the direction of wave propagation. For a wave spreading uniformly from a point source, the intensity decreases with the square of the distance: I ∝ 1/r².
强度是垂直于波传播方向上的每单位面积所传递的功率。对于从点源均匀传播的波，强度随距离的平方而减小：I ∝ 1/r²。
Light is an electromagnetic transverse wave, while sound is a longitudinal mechanical wave. When a wave reflects, refracts, or diffracts, its frequency remains constant; however, the wavelength and speed may change when the medium changes.
光是电磁横波，而声音是纵波（机械波）。当波发生反射、折射或衍射时，其频率保持不变；但当介质改变时，波长和波速可能发生变化。
When drawing wave diagrams, pay careful attention to the distinction between displacement-distance graphs (showing the wave at a single instant) and displacement-time graphs (showing the motion of a single particle). The former gives wavelength directly, while the latter gives the period.
画波图时，要仔细区分位移-距离图像（显示某一时刻的波）和位移-时间图像（显示单个质点的运动）。前者直接给出波长，后者给出周期。
7. Superposition and Interference | 叠加与干涉
The principle of superposition states that when two or more waves meet at a point, the resultant displacement is the vector sum of the individual displacements. This leads to the phenomena of interference and stationary (standing) waves.
叠加原理指出，当两列或更多列波在同一点相遇时，合位移等于各列波位移的矢量和。这导致了干涉现象和驻波的产生。
For two coherent sources of waves (sources with a constant phase difference and the same frequency), constructive interference occurs when the path difference between the two waves is a whole number of wavelengths. Destructive interference occurs when the path difference is an odd number of half-wavelengths.
对于两个相干波源（频率相同且相位差恒定的波源），当两列波的波程差等于波长的整数倍时，发生相长干涉；当波程差等于半波长的奇数倍时，发生相消干涉。
Constructive: path difference = nλ (n = 0, 1, 2, …)
Destructive: path difference = (n + ½)λ (n = 0, 1, 2, …)
In Young’s double-slit experiment, the fringe spacing Δx observed on a screen is related to the wavelength λ, the distance D from the slits to the screen, and the slit separation d by the equation Δx = λD / d. This is a core experiment in the AS specification.
在杨氏双缝实验中，屏幕上观察到的条纹间距 Δx 与波长 λ、双缝到屏幕的距离 D 以及双缝间距 d 的关系为 Δx = λD / d。这是 AS 考纲中的核心实验。
A stationary wave is formed when two waves of equal frequency and amplitude travel in opposite directions through the same medium. Nodes are points of zero displacement, while antinodes are points of maximum displacement. Adjacent nodes are separated by λ/2.
当频率和振幅相同的两列波在同一介质中沿相反方向传播时，会形成驻波。波节是位移始终为零的点，波腹是位移最大的点。相邻波节之间的距离为 λ/2。
8. Electric Current and DC Circuits | 电流与直流电路
Electric current is the rate of flow of charge. It is measured in amperes (A), where 1 A = 1 C s⁻¹. For a steady current, the charge ΔQ flowing past a point in time Δt is given by I = ΔQ / Δt. In a metallic conductor, current is carried by free electrons.
电流是电荷流动的速率，单位为安培（A），其中 1 A = 1 C s⁻¹。对于恒定电流，在时间 Δt 内通过某一点的电荷量为 ΔQ，满足 I = ΔQ / Δt。在金属导体中，电流由自由电子携带。
Voltage, or potential difference (p.d.), is the work done per unit charge in moving charge between two points. It is measured in volts, where 1 V = 1 J C⁻¹. Resistance is defined as the ratio of voltage to current.
电压（电位差）是移动单位电荷通过两点之间所做的功，单位为伏特，其中 1 V = 1 J C⁻¹。电阻定义为电压与电流之比。
V = IR
Ohm’s law states that for a metallic conductor at constant temperature, the current is directly proportional to the potential difference. This is a linear relationship, and the I-V characteristic is a straight line through the origin. A semiconductor diode, by contrast, conducts in only one direction and has a non-linear I-V characteristic.
欧姆定律指出，在恒定温度下，金属导体中的电流与电位差成正比。这是线性关系，I-V 特性曲线为通过原点的直线。相比之下，半导体二极管仅在一个方向导通，其 I-V 特性曲线是非线性的。
For resistors in series, the total resistance is the sum of the individual resistances. For resistors in parallel, the reciprocal of the total resistance equals the sum of the reciprocals of the individual resistances.
串联电阻时，总电阻等于各分电阻之和。并联电阻时，总电阻的倒数等于各分电阻倒数之和。
Rₛ = R₁ + R₂ + R₃ (series)
1/Rₚ = 1/R₁ + 1/R₂ + 1/R₃ (parallel)
The resistivity ρ of a material is related to its resistance by the equation R = ρL / A, where L is the length and A is the cross-sectional area of the conductor. Resistivity is a property of the material and is measured in ohm-metres (Ω m).
材料的电阻率 ρ 与电阻的关系为 R = ρL / A，其中 L 是导体的长度，A 是横截面积。电阻率是材料本身的属性，单位为欧姆·米（Ω m）。
9. EMF and Internal Resistance | 电动势与内阻
Every real battery has an internal resistance r, which causes a loss of potential difference when current flows. The electromotive force (EMF) ε of a source is the total energy supplied per unit charge by the source, while the terminal potential difference is the voltage available at the terminals of the battery.
每个真实电池都存在内阻 r，当有电流流过时会导致电位差损失。电源的电动势 ε 是电源提供给每单位电荷的总能量，而端电压是电池两端可用的电压。
The relationship between EMF, terminal p.d., current, internal resistance, and external load resistance R is given by the equation below. This is one of the most commonly tested equations in AS electricity topics.
电动势、端电压、电流、内阻和外接负载电阻 R 之间的关系由以下方程给出。这是 AS 电学部分最常见的考点方程之一。
ε = I(R + r) = IR + Ir
Here, IR is the terminal potential difference, and Ir is the ‘lost volts’ across the internal resistance. When the battery is short-circuited, R = 0 and the maximum current flows, limited only by the internal resistance. When the
Published by TutorHao | AS Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
屏轩国际教育cambridge primary/secondary checkpoint, cat4, ukiset,ukcat,igcse,alevel,PAT,STEP,MAT, ibdp,ap,ssat,sat,sat2课程辅导，国外大学本科硕士研究生博士课程论文辅导