📚 Year 11 WJEC Physics: Core Knowledge Summary | Year 11 WJEC 物理：核心知识点梳理
As Year 11 students approach their WJEC GCSE Physics exams, a clear summary of core topics is essential for effective revision. This article covers the fundamental concepts from motion and forces to electricity, waves, radioactivity and space physics, aligned with the WJEC specification for both Unit 1 and Unit 2. Each section presents key equations, definitions and real-world applications to support exam success.
对于 Year 11 学生来说，在备考 WJEC GCSE 物理时，梳理核心知识点至关重要。本文涵盖了从运动与力到电学、波、放射性和空间物理的基本概念，与 WJEC 单元一和单元二的大纲保持一致。每个小节都提供了关键公式、定义和实际应用，帮助你在考试中取得好成绩。
1. Motion and Forces | 运动与力
Speed is the rate of change of distance, while velocity includes direction. Acceleration describes how quickly velocity changes over time and is calculated using the equation below.
速率是距离的变化率，而速度包含方向。加速度描述了速度随时间变化的快慢，可用以下公式计算。
a = (v − u) / t
Where u is initial velocity, v is final velocity and t is the time taken. The SUVAT equation for displacement involves initial velocity, acceleration and time.
其中 u 是初速度，v 是末速度，t 是时间。计算位移的匀加速运动公式涉及初速度、加速度和时间。
s = u t + ½ a t²
Newton' object remains at rest or in uniform motion unless acted upon by a resultant force. Newton' ration: F = m a. Weight is the force due to gravity, W = m g, where g ≈ 9.8 m/s² on Earth.
牛顿第一定律指出，除非受到净力作用，否则物体会保持静止或匀速直线运动。牛顿第二定律将力、质量和加速度联系起来：F = m a。重力是物体受到的引力，W = m g，地球表面 g ≈ 9.8 m/s²。
Stopping distance is the sum of thinking distance and braking distance. Factors such as speed, reaction time and road conditions affect these distances. Momentum is the product of mass and velocity, and in collisions total momentum is conserved.
制动距离是反应距离和刹车距离的总和。速度、反应时间和路面状况等因素会影响这些距离。动量是质量与速度的乘积，在碰撞中总动量守恒。
2. Energy, Work and Power | 能量、功和功率
Energy can be stored in different forms, including kinetic, gravitational potential, thermal, chemical and nuclear. The principle of conservation of energy states that energy cannot be created or destroyed, only transferred or converted.
能量可以多种形式储存，包括动能、重力势能、热能、化学能和核能。能量守恒定律指出，能量不能被创造或消灭，只能转移或转化。
Kinetic energy (KE) depends on mass and speed, while gravitational potential energy (GPE) depends on mass, height and gravitational field strength.
动能取决于质量和速度，而重力势能取决于质量、高度和引力场强度。
KE = ½ m v² and GPE = m g h
s the rate of energy transfer or work done: P = E / t or P = W / t, measured in watts (W).
力对物体做功时，功等于力乘以在力的方向上移动的距离：W = F d。功率是能量传递或做功的速率：P = E / t 或 P = W / t，单位为瓦特（W）。
Efficiency is the ratio of useful output energy to total input energy, often expressed as a percentage. In any energy transfer, some energy is dissipated, usually as thermal energy, which reduces efficiency.
效率是有用输出能量与总输入能量之比，通常以百分比表示。在任何能量转移过程中，总会有一部分能量耗散，通常是以热能形式，这降低了效率。
3. Features of Waves | 波的特征
Waves transfer energy without transferring matter. Transverse waves have oscillations perpendicular to the direction of energy transfer (e.g. light, water waves), while longitudinal waves have oscillations parallel to the direction (e.g. sound, seismic P-waves).
波传递能量而不传递物质。横波的振动方向与能量传递方向垂直（如光波、水波），而纵波的振动方向与能量传递方向平行（如声波、地震P波）。
The key wave properties are amplitude, wavelength (λ), frequency (f) and wave speed (v). The wave equation links these quantities.
波的主要特性包括振幅、波长（λ）、频率（f）和波速（v）。波动方程将这些量联系起来。
v = f λ
Reflection occurs when waves bounce off a surface, obeying the law of reflection. Refraction involves the change in speed and direction when waves cross a boundary between two media of different densities.
反射发生在波碰到表面反弹时，遵循反射定律。折射是波穿过两种不同密度介质边界时速度和方向的改变。
Total internal reflection happens when the angle of incidence exceeds the critical angle and the wave cannot pass into the less dense medium. Seismic waves provide evidence about the Earth's interior, with P-waves travelling through solids and liquids, and S-waves only through solids.
当入射角大于临界角且波无法进入光疏介质时，会发生全内反射。地震波为地球内部结构提供了证据，P波能在固体和液体中传播，而S波只能在固体中传播。
4. Electromagnetic Spectrum and Optics | 电磁波谱与光学
at the speed of light in a vacuum (c ≈ 3.0 × 10⁸ m/s) but differ in wavelength and frequency.
电磁波谱包括无线电波、微波、红外线、可见光、紫外线、X射线和伽马射线。它们在真空中都以光速 c ≈ 3.0 × 10⁸ m/s 传播，但波长和频率不同。
| Radiation | Typical wavelength | Uses |
|---|---|---|
| Radio | > 0.1 m | Communications, broadcasting |
| Microwave | 1 mm – 0.1 m | Cooking, satellite signals |
| Infrared | 700 nm – 1 mm | Thermal imaging, remote controls |
| Visible light | 400 nm – 700 nm | Vision, photography |
| Ultraviolet | 10 nm – 400 nm | Sterilisation, sun tanning |
| X-rays | 0.01 nm – 10 nm | Medical imaging, security |
| Gamma | < 0.01 nm | Cancer treatment, sterilisation |
In optics, a convex lens converges light rays to a focal point; the focal length depends on the curvature of the lens. Real and virtual images can be formed, with magnification calculated by image height/object height.
在光学中，凸透镜使光线会聚到焦点；焦距取决于透镜的曲率。可以形成实像和虚像，放大率 = 像高/物高。
5. Electric Circuits | 电路基础
amperes (A), charge Q in coulombs (C) and time t in seconds. The relationship is Q = I t.
电流是电荷的流动。电流 I 以安培（A）为单位，电荷 Q 以库仑（C）为单位，时间 t 以秒为单位。关系为 Q = I t。
rent and is defined as R = V / I (Ohm’s law for a fixed resistor at constant temperature).
电势差（电压）是每单位电荷转移的能量：V = W / Q。电阻阻碍电流流动，定义为 R = V / I（固定电阻在恒温下的欧姆定律）。
everywhere, and the total resistance is the sum of individual resistances: Rₛ = R₁ + R₂ + … total current is the sum of branch currents. Total resistance follows 1/Rₚ = 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：Rₛ = R₁ + R₂ + … 。电源电压在各元件间分配。在并联电路中，各支路电压相同，总电流等于各支路电流之和。总电阻满足 1/Rₚ = 1/R₁ + 1/R₂。
y transferred E = P t, often expressed in joules or kilowatt-hours (kWh) for domestic use.
电功率可用 P = I V 或 P = I² R 计算。能量转移 E = P t，常用焦耳或千瓦时（kWh）表示，后者用于家庭用电。
6. Domestic Electricity and Safety | 家庭用电与安全
In the UK, mains electricity is supplied as alternating current (AC) at about 230 V and a frequency of 50 Hz. Plugs contain a live wire (brown), a neutral wire (blue) and an earth wire (green/yellow).
英国的家庭用电为交流电 (AC)，约 230 V，频率 50 Hz。插头包含火线（棕色）、零线（蓝色）和地线（绿/黄色）。
The earth wire provides a safe path for current if a fault occurs, preventing the metal case from becoming live. Fuses and circuit breakers are safety devices that disconnect the circuit when current exceeds a safe value. Double-insulated appliances have no earth wire because their outer case is non-conductive.
地线在发生故障时提供安全的电流通路，防止金属外壳带电。保险丝和断路器是安全装置，当电流超过安全值时断开电路。双重绝缘电器没有地线，因为其外壳不导电。
ansfer can be compared using the equation: energy transferred (kWh) = power (kW) × time (h).
家庭用电量以千瓦时计量。费用 = 用电量 (kWh) × 单价。可以通过公式：能量转移 (kWh) = 功率 (kW) × 时间 (h) 来比较。
7. Magnetism and Electromagnetism | 磁学与电磁学
A magnet has north and south poles; like poles repel and unlike poles attract. Magnetic field lines point from north to south and show the direction of force on a north pole. An electromagnet consists of a coil of wire (solenoid) wrapped around a soft iron core, producing a strong magnetic field when current flows.
磁铁有南北极；同极相斥，异极相吸。磁感线从北极指向南极，显示北极受力的方向。电磁铁由绕在软铁芯上的线圈（螺线管）构成，通电时产生强磁场。
The motor effect occurs when a current-carrying conductor is placed in a magnetic field, experiencing a force. Fleming's left-hand rule gives the direction of force (thumb), magnetic field (first finger) and current (second finger). This principle is used in electric motors.
当载流导体置于磁场中时会受到力，这就是电动机效应。弗莱明左手定则确定了力的方向（拇指）、磁场方向（食指）和电流方向（中指）。该原理应用于电动机。
Electromagnetic induction is the generation of a voltage when a conductor cuts magnetic field lines. Generators and dynamos use this to produce electricity. An alternator produces AC, while a dynamo with a split-ring commutator produces DC.
电磁感应是导体切割磁感线时产生电压的现象。发电机和发电机就是用此原理发电。交流发电机产生交流电，而带换向器的直流发电机产生直流电。
8. Atomic Structure and Radioactivity | 原子结构与放射性
roton) number Z defines the element, and the mass number A = number of protons + neutrons.
原子由包含质子（正电）和中子（中性）的原子核及在壳层中运动的电子组成。原子序数（质子数）Z 决定元素种类，质量数 A = 质子数 + 中子数。
Isotopes are atoms of the same element with different numbers of neutrons. Unstable isotopes decay by emitting radiation. The three main types are alpha (α), beta minus (β⁻) and gamma (γ).
同位素是质子数相同但中子数不同的原子。不稳定同位素通过辐射衰变。三种主要类型是 α、β⁻ 和 γ。
| Property | Alpha (α) | Beta (β⁻) | Gamma (γ) |
|---|---|---|---|
| Nature | Helium nucleus, ⁴₂He | Fast electron | Electromagnetic wave |
| Penetration | Stopped by paper/skin | Stopped by few mm aluminium | Reduced by thick lead or concrete |
| Ionising power | Very high | Medium | Low |
Nuclear equations show the changes in mass and proton numbers during decay. For alpha decay, mass number decreases by 4 and proton number by 2. For beta decay, a neutron turns into a proton, increasing proton number by 1 while mass number remains unchanged.
核方程显示了衰变过程中质量数和质子数的变化。α 衰变质量数减少 4，质子数减少 2。β 衰变中，一个中子转变为质子，质子数增加 1，质量数不变。
9. Half-life and Nuclear Energy | 半衰期与核能
Half-life is the time taken for the radioactivity of a sample to fall to half its original value. It is a constant for a given isotope and is used in radioactive dating, such as carbon-14 dating for organic remains.
半衰期是放射性样品的活度下降到初始值一半所需的时间。对于给定同位素，半衰期是常数，常用于放射性定年，例如用碳-14 测定有机遗骸年代。
e background radiation comes from natural sources like radon gas, cosmic rays and rocks, and must be subtracted when measuring net count rate.
放射性活度以贝克勒尔 (Bq) 为单位，1 Bq = 每秒钟 1 次衰变。本底辐射来自氡气、宇宙射线和岩石等天然来源，测量净计数率时必须扣除。
Nuclear fission is the splitting of a large nucleus (e.g. ²³⁵U or ²³⁹Pu) into smaller nuclei, releasing energy and neutrons. These neutrons can trigger a chain reaction. In nuclear power stations, controlled fission heats water to produce steam that drives turbines.
核裂变是大核（如 ²³⁵U 或 ²³⁹Pu）分裂成较小的核，释放能量和中子。这些中子可以引发链式反应。在核电站中，受控裂变加热水产生蒸汽驱动涡轮机。
Nuclear fusion is the joining of small nuclei (e.g. hydrogen isotopes) to form a larger nucleus, releasing vast amounts of energy. This process powers the Sun but is difficult to achieve on Earth due to the extremely high temperatures required.
核聚变是小核（如氢的同位素）结合成较大核，释放巨大能量。这一过程为太阳提供能量，但在地球上很难实现，因为需要极高温度。
10. Space Physics and the Universe | 空间物理与宇宙
it the Sun in elliptical paths, held in place by gravitational attraction: F = G M m / r².
我们的太阳系由太阳、八大行星、矮行星、卫星、小行星和彗星组成。行星在引力作用下沿椭圆轨道绕太阳运行：F = G M m / r²。
d giant → planetary nebula → white dwarf. More massive stars become red supergiants and end in a supernova, leaving behind a neutron star or black hole.
恒星由在引力下坍缩的气体和尘埃云（星云）形成。类似太阳的恒星生命周期：原恒星 → 主序星 → 红巨星 → 行星状星云 → 白矮星。质量更大的恒星成为红超巨星，以超新星爆发结束，留下中子星或黑洞。
Observations of distant galaxies show that light from them is shifted towards the red end of the spectrum (redshift). This indicates that galaxies are moving away from us, providing evidence that the Universe is expanding. The Big Bang theory states that the Universe began from an extremely hot, dense point about 13.8 billion years ago and cosmic microwave background radiation is leftover energy from that event.
对遥远星系的观测显示，它们的光谱向红端移动（红移）。这表明星系正在远离我们，为宇宙膨胀提供了证据。大爆炸理论认为，宇宙约在 138 亿年前从一个极热、致密的点开始，宇宙微波背景辐射是该事件的残余能量。
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