📚 Year 11 Edexcel Physics: Core Knowledge Summary | Year 11 Edexcel 物理：核心知识点梳理
This article brings together the most important topics from Year 11 Edexcel Physics, designed to help you consolidate your knowledge ahead of the final exams. Each section is presented with clear English explanations followed by matching Chinese translations, covering forces, motion, energy, waves, electricity, the particle model and radioactivity. Mastering these fundamentals will give you a strong foundation for both Paper 1 and Paper 2.
本文汇集了 Year 11 Edexcel 物理课程中最重要的主题，旨在帮助你在期末考试前巩固知识。每个部分都配有清晰的英文解释和对应的中文翻译，涵盖力、运动、能量、波、电、粒子模型和放射性等核心内容。掌握这些基础知识将为你应对 Paper 1 和 Paper 2 打下坚实的基础。
1. Motion and SUVAT Equations | 运动与 SUVAT 方程
Speed is a scalar quantity that describes how fast an object is moving, calculated by dividing the distance travelled by the time taken: v = s / t. Velocity, on the other hand, is a vector – it includes both speed and direction. In everyday contexts, going around a corner at constant speed means velocity is changing because direction changes.
速率是标量，描述物体移动的快慢，由移动的距离除以所用时间计算得出：v = s / t。而速度则是矢量，既包含快慢也包含方向。在日常场景中，以恒定速率转弯时速度是变化的，因为方向发生了变化。
Acceleration measures how quickly velocity changes: a = (v – u) / t, where u is initial velocity and v is final velocity. A positive acceleration means speeding up in the chosen direction, while negative acceleration (deceleration) means slowing down. All objects in free fall near the Earth's surface accelerate downwards at approximately 9.8 m/s², regardless of mass, when air resistance is negligible.
加速度衡量速度变化的快慢：a = (v – u) / t，其中 u 是初速度，v 是末速度。正的加速度表示在所选方向上加速，负的加速度（减速）表示减速。忽略空气阻力时，地球表面附近所有自由下落的物体均以约 9.8 m/s² 的加速度向下运动，与质量无关。
The four equations of motion for constant acceleration – often called SUVAT – are: v = u + at, v² = u² + 2as, s = ut + ½at² and s = ½(u + v)t. These equations link displacement (s), initial velocity (u), final velocity (v), acceleration (a) and time (t). You must be able to select the correct equation and solve problems involving a missing variable.
用于匀加速运动的四个运动学方程——常被称为 SUVAT——为：v = u + at、v² = u² + 2as、s = ut + ½at² 和 s = ½(u + v)t。这些方程将位移（s）、初速度（u）、末速度（v）、加速度（a）和时间（t）联系起来。你必须能够选择合适的方程并求解含有一个未知变量的问题。
2. Forces and Newton's Laws | 力与牛顿定律
types include weight (W = mg), normal reaction, friction, tension, air resistance, and upthrust. The resultant force on an object determines its motion; if forces are balanced, the object moves at constant velocity or stays at rest.
力是物体间相互作用时产生的推或拉。力是矢量，单位为牛顿（N）。常见的力包括重力（W = mg）、法向反作用力、摩擦力、拉力、空气阻力和浮力。物体所受的合力决定其运动状态；若合力为零，物体将保持匀速直线运动或静止。
Newton's First Law states that an object will remain at rest or in uniform motion unless acted upon by a resultant force. Newton's Second Law expresses the link between force, mass and acceleration: F = ma. This means a larger force produces a larger acceleration, and a larger mass requires a larger force for the same acceleration. Newton's Third Law reminds us that forces always occur in equal and opposite pairs acting on different objects.
牛顿第一定律指出，物体在没有受到合力作用时，将保持静止或匀速直线运动。牛顿第二定律给出了力、质量和加速度之间的关系：F = ma。这意味着更大的力产生更大的加速度，而更大的质量需要更大的力才能达到相同的加速度。牛顿第三定律则强调力总是成对出现，大小相等、方向相反且作用在不同物体上。
3. Momentum | 动量
Momentum is the product of an object's mass and velocity: p = mv. It is a vector quantity conserved in a closed system, meaning the total momentum before a collision or explosion equals the total momentum after, provided no external forces act. This principle underpins safety features such as seat belts, air bags and crumple zones, which increase the time over which a collision occurs, reducing the force experienced.
动量是物体质量与速度的乘积：p = mv。它是矢量，在一个封闭系统中守恒，即只要没有外力作用，碰撞或爆炸前的总动量等于碰撞或爆炸后的总动量。这一原理是安全带、安全气囊和溃缩区等安全设计的基础，因为它们延长了碰撞发生的时间，从而减小了作用力。
You should be able to perform calculations using the conservation law, for instance determining the recoil velocity of a gun or the common velocity of two objects that stick together after impact. The force–momentum relationship F = Δp / t shows why rapid momentum changes cause large forces.
你应该能够运用动量守恒定律进行计算，例如确定枪的反冲速度或两个碰撞后粘在一起的物体的共同速度。力与动量的关系式 F = Δp / t 解释了为什么动量的快速变化会产生巨大的力。
4. Work, Energy and Power | 功、能与功率
Energy is stored in different forms: kinetic, gravitational potential, elastic, thermal, chemical and nuclear. The principle of conservation of energy states that energy cannot be created or destroyed, only transferred from one store to another. When a system changes, the total energy before always equals the total energy after, although some is often dissipated to the thermal store of the surroundings.
能量以不同的形式储存：动能、重力势能、弹性势能、热能、化学能和核能。能量守恒定律表明，能量既不能凭空产生，也不能凭空消失，只能从一种储存形式转移到另一种。系统发生变化时，变化前的总能量总是等于变化后的总能量，尽管部分能量往往会耗散到周围环境的热能储存中。
Work done is the means by which energy is transferred mechanically: W = Fd, where work is in joules when a force F moves an object through a distance d in the direction of the force. Gravitational potential energy gained when lifting is ΔEp = mgΔh, and kinetic energy is Ek = ½mv². Power is the rate of energy transfer: P = E / t, measured in watts (W).
功是通过机械方式传递能量的途径：W = Fd，当力 F 使物体沿力的方向移动距离 d 时，做功的单位为焦耳。提升物体所增加的重力势能为 ΔEp = mgΔh，动能为 Ek = ½mv²。功率是能量传递的速率：P = E / t，单位为瓦特（W）。
Efficiency measures how much of the input energy is converted to useful output: efficiency = useful energy output / total energy input (often multiplied by 100 for a percentage). No device is 100% efficient due to friction, air resistance and electrical heating.
效率衡量输入能量中有多少转化为有用的输出：效率 = 有用的能量输出 / 总能量输入（常乘以 100 以百分比表示）。由于摩擦、空气阻力和电热效应，没有器件能达到 100% 的效率。
5. Wave Basics | 波的基础
Waves transfer energy from one place to another without transferring matter. In transverse waves, such as light and water ripples, the oscillations are perpendicular to the direction of energy transfer. In longitudinal waves, such as sound, the oscillations are parallel to the direction of energy transfer, forming compressions and rarefactions.
波能将能量从一个地方传递到另一个地方，而不会传递物质。在横波（例如光和水波）中，振动方向与能量传递方向垂直。在纵波（例如声波）中，振动方向与能量传递方向平行，形成疏密相间的区域。
ints in phase), frequency (f, the number of complete waves passing a point per second, in hertz) and period (T = 1/f). The wave equation links these: v = fλ, where v is the wave speed.
波的关键属性包括振幅（偏离平衡位置的最大位移）、波长（λ，两个连续同相点之间的距离）、频率（f，每秒通过某点的完整波的数目，单位为赫兹）和周期（T = 1/f）。波速方程将它们联系起来：v = fλ，其中 v 为波速。
All waves can be reflected, refracted and diffracted. Refraction occurs when a wave changes speed upon entering a new medium, causing the wavelength – and sometimes the direction – to change. Diffraction is the spreading out of waves when they pass through a gap or around an obstacle, most noticeable when the gap size is similar to the wavelength.
所有波都可发生反射、折射和衍射。折射是波进入新介质时速度改变，导致波长（有时还有传播方向）发生变化的现象。衍射是波在通过狭缝或绕过障碍物时扩散的现象，当狭缝尺寸与波长相当时最为显著。
6. The Electromagnetic Spectrum | 电磁波谱
Electromagnetic (EM) waves are transverse waves that travel at the same speed in a vacuum – ectrum, in order of increasing frequency and decreasing wavelength, consists of: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays. Each region has distinct properties, uses and hazards.
电磁波是横波，在真空中以相同速度传播——约 3.0 × 10⁸ m/s。电磁波谱按频率递增、波长递减的顺序依次为：无线电波、微波、红外线、可见光、紫外线、X 射线和伽马射线。每个波段都具有不同的性质、用途和危害。
Radio waves are used for television and radio communication; microwaves for satellite signals and cooking; infrared for thermal imaging and remote controls; visible light enables vision and optical fibres; ultraviolet is used in fluorescent lamps and tanning but can cause skin cancer; X-rays pass through soft tissue for medical imaging; gamma rays are emitted by radioactive nuclei, used for sterilising equipment and treating cancer, but are highly ionising and dangerous.
无线电波用于电视和无线电通讯；微波用于卫星信号和烹饪；红外线用于热成像和遥控器；可见光使人视物，并用于光纤通讯；紫外线用于荧光灯和晒黑，但可能导致皮肤癌；X 射线穿透软组织，用于医疗成像；伽马射线由放射性原子核发出，用于设备灭菌和癌症治疗，但电离能力强，十分危险。
All EM waves transfer energy and can be absorbed or transmitted by different materials. The higher the frequency, the more ionising and therefore more hazardous the radiation tends to be. Overexposure to ultraviolet, X-rays and gamma rays requires protective measures.
所有电磁波都能传递能量，并可以被不同材料吸收或透射。频率越高，电离能力通常越强，因此危害也越大。过度暴露于紫外线、X 射线和伽马射线时需要采取防护措施。
7. Electricity: Fundamentals | 电学基础
Electric current is the rate of flow of charge: I = Q / t, measured in amperes (A). For a current to flow continuously, a complete circuit with a source of potential difference (voltage) is needed. Conventional current flows from the positive terminal to the negative terminal of a cell, while electrons actually move in the opposite direction.
电流是电荷流动的速率：I = Q / t，单位为安培（A）。要让电流持续流动，需要一个具有电势差（电压）源的完整回路。常规电流从电池的正极流向负极，而电子实际上以相反方向运动。
Potential difference (voltage) is the energy transferred per unit of charge: V = E / Q. Resistance opposes the flow of current and is defined by Ohm's law: V = IR, where resistance R is measured in ohms (Ω). An ohmic conductor maintains a constant resistance at constant temperature, giving a straight-line I–V graph through the origin.
电势差（电压）是每单位电荷传递的能量：V = E / Q。电阻阻碍电流的流动，由欧姆定律定义：V = IR，其中电阻 R 的单位为欧姆（Ω）。欧姆导体在温度恒定时保持电阻不变，其 I–V 特性曲线为一条通过原点的直线。
In series circuits, current is the same everywhere, while the total resistance is the sum of individual resistances: Rtotal = R₁ + R₂ + …. In parallel circuits, the total current is shared between branches, and more than one resistance added in parallel actually lowers the total resistance. Calculations involve combining fractions: 1/Rtotal = 1/R₁ + 1/R₂.
在串联电路中，各处电流相同，总电阻等于各电阻之和：R总 = R₁ + R₂ + …。在并联电路中，总电流在各支路间分配，增加并联支路实际上会降低总电阻。计算时需要合并倒数：1/R总 = 1/R₁ + 1/R₂。
8. Circuit Components | 电路元件
Common circuit components have characteristic I–V graphs that help predict their behaviour. A fixed resistor at constant temperature obeys Ohm's law. A filament lamp does not: as current increases, the wire heats up and its resistance rises, resulting in a curved I–V graph that becomes less steep. A diode allows current to flow in only one direction; it has very high resistance in reverse, shown by a near-zero current for negative voltages.
常见电路元件具有各自的 I–V 特性曲线，可帮助预测其行为。定值电阻在温度恒定时遵循欧姆定律。灯丝灯泡则不同：电流增大时灯丝升温，电阻升高，其 I–V 曲线变得弯曲且斜率减小。二极管只允许电流单向导通；反向时电阻极高，对应负电压下电流几乎为零。
Thermistors and light-dependent resistors (LDRs) are sensing devices. The resistance of a thermistor decreases as temperature rises, making it useful in thermostats. An LDR's resistance falls as light intensity increases, so it is used in automatic street lights. In potential divider circuits, these components vary the output voltage, allowing control of other components.
热敏电阻和光敏电阻（LDR）是传感元件。热敏电阻的阻值随温度升高而减小，可用于恒温器。光敏电阻的阻值随光照增强而减小，因此常用于自动路灯。在分压电路中，这些元件能改变输出电压，从而控制其它器件。
9. Mains Electricity and Energy Transfers | 市电与能量转移
In the UK, mains electricity is an alternating current (AC) with a frequency of 50 Hz and a voltage of about 230 V. AC means the current repeatedly changes direction, unlike the direct current (DC) from cells and batteries. Live, neutral and earth wires form a standard three-pin plug; the earth wire provides a low-resistance path to ground, protecting users if a fault occurs.
在英国，市电是频率为 50 Hz、电压约 230 V 的交流电（AC）。交流电意味着电流方向不断交替变化，这与电池提供的直流电（DC）不同。标准三脚插头中包含火线、零线和地线；地线提供一条低电阻接地通路，在发生故障时保护使用者。
Electrical power is the rate of electrical energy transfer: P = IV and, using Ohm's law, P = I²R = V²/R. Energy transferred over time is E = Pt = IVt 0⁶ J. Fuses and circuit breakers are safety devices that break the circuit if the current exceeds a safe value.
电功率是电能传递的速率：P = IV，利用欧姆定律还可写为 P = I²R = V²/R。一段时间内传递的电能为 E = Pt = IVt，单位为焦耳。在日常生活中，电能常以千瓦时（kWh）计费，1 kWh = 3.6 × 10⁶ J。保险丝和断路器是安全装置，当电流超过安全值时会切断电路。
10. Particle Model and Gas Pressure | 粒子模型与气体压强
The particle model describes matter as tiny, moving particles. Solids have a fixed shape because particles vibrate in fixed positions; liquids take the shape of their container as particles can slide past each other; gases spread to fill any container because particles move rapidly in all directions. Increasing temperature increases the average kinetic energy of the particles, which can cause changes of state without a change of mass.
粒子模型将物质描述为由不断运动的微小粒子组成。固体的形状固定，因为粒子只能在固定位置振动；液体具有流动性，因为粒子可以彼此滑过；气体则充满整个容器，因为粒子快速向各个方向运动。温度升高会使粒子的平均动能增加，从而导致物态变化但质量不变。
Absolute zero is the lowest possible temperature (0 K or –273 °C), where particles have the minimum possible energy. Pressure in a gas is caused by particles colliding with the walls of the container. For a fixed mass of gas at constant volume, pressure is proportional to absolute temperature: p ∝ T or p₁/T₁ = p₂/T₂. If the volume is changed while temperature stays constant, pressure and volume are inversely proportional: pV = constant (Boyle's law).
绝对零度是可能的最低温度（0 K 或 –273 °C），此时粒子的能量最低。气体的压强是由粒子与容器壁碰撞产生的。对于一定质量的气体，若体积不变，压强与绝对温度成正比：p ∝ T 或 p₁/T₁ = p₂/T₂。若温度不变而体积改变，则压强与体积成反比：pV = 常数（玻意耳定律）。
Density tells us how compact a material is: ρ = m / V. An object will float if its density is lower than that of the fluid it displaces; upthrust equals the weight of fluid displaced. Internal energy is the total energy stored by the particles – the sum of kinetic and potential energies. During a change of state, temperature stays constant while internal energy continues to be transferred.
密度表示材料的致密程度：ρ = m / V。若物体的密度小于所排开流体的密度，它将上浮；浮力等于排开流体的重量。内能是粒子储存的总能量——即动能与势能之和。在物态变化过程中，温度保持不变，但内能仍在继续转移。
11. Radioactivity | 放射性
Atoms contain a nucleus made of protons and neutrons, surrounded by electrons. Unstable nuclei emit radiation to become more stable, a process called radioactive decay. There are three main types of nuclear radiation: alpha (α) particles (helium nuclei, ⁴₂He), beta (β) particles (high‑speed electrons) and gamma (γ) rays (electromagnetic waves). Each has different penetrating power, ionising ability and behaviour in electric and magnetic fields.
原子包含由质子和中子组成的原子核，核外有电子。不稳定的原子核会发出辐射以变得更稳定，这一过程称为放射性衰变。核辐射主要有三种类型：α 粒子（氦原子核，⁴₂He）、β 粒子（高速电子）和 γ 射线（电磁波）。它们的穿透能力、电离本领以及在电场和磁场中的行为各不相同。
During alpha decay, the mass number decreases by 4 and the atomic number by 2. In beta decay, a neutron turns into a proton, emitting an electron; the mass number stays the same and the atomic number increases by 1. Gamma rays often accompany alpha or beta decay and carry away excess energy without changing the nucleus's structure. Nuclear equations must balance mass and atomic numbers.
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