📚 Year 11 WJEC Physics: Core Knowledge Review | Year 11 WJEC 物理：核心知识点梳理
Welcome to the essential Year 11 WJEC Physics revision guide. This article summarises the core knowledge you must master for your GCSE examinations, covering electricity, forces, motion, waves, radioactivity and space. Use this structured walkthrough to reinforce your understanding and build confidence ahead of your assessments.
欢迎来到 Year 11 WJEC 物理核心复习指南。本文梳理了 GCSE 考试必须掌握的关键知识点，涵盖电学、力学、运动学、波、放射性和空间物理。利用这份结构化梳理巩固理解，为考前冲刺增添信心。
1. Electric Charge, Current and Circuits | 电荷、电流与电路
An electric current is a flow of electric charge. In metal wires, the charge carriers are free electrons. Current (I) is measured in amperes (A); one ampere represents one coulomb (C) of charge passing a point per second.
电流是电荷的流动。在金属导线中，载流子是自由电子。电流 (I) 以安培 (A) 为单位；1 安培表示每秒有 1 库仑 (C) 电荷通过某一点。
For a current to flow, a complete circuit is needed, along with a source of potential difference (voltage). Potential difference (V) is the energy transferred per unit charge and is measured in volts (V). A volt equals one joule per coulomb.
形成电流需要完整的回路和电势差（电压）。电势差 (V) 是每单位电荷转移的能量，单位为伏特 (V)。1 伏特等于 1 焦耳每库仑。
Circuit components are represented by standard symbols. Key symbols include: a cell (two parallel lines, one longer), a battery (multiple cells), a resistor (rectangle), a variable resistor (rectangle with an arrow), a lamp (circle with a cross), a switch, an ammeter (circle with A) and a voltmeter (circle with V).
电路元件用标准符号表示。常见符号有：电池（一长一短平行线）、电阻（矩形）、可变电阻（带箭头的矩形）、小灯泡（带叉的圆）、开关、电流表（带 A 的圆）和电压表（带 V 的圆）。
2. Ohm's Law and Resistance | 欧姆定律与电阻
Ohm's Law states that, at constant temperature, the current through a conductor is directly proportional to the potential difference across it. The relationship is expressed as:
V = I × R
欧姆定律指出：在温度恒定的条件下，通过导体的电流与其两端的电势差成正比。关系式为：V = I × R
Resistance (R) is measured in ohms (Ω). A component obeys Ohm's law if its resistance remains constant. For a fixed resistor at constant temperature, the I–V graph is a straight line through the origin.
电阻 (R) 的单位为欧姆 (Ω)。若元件的电阻恒定，它就遵循欧姆定律。对于温度不变的固定电阻，其 I–V 图像是一条过原点的直线。
Resistance depends on material, length and cross-sectional area. A longer wire has higher resistance; a thicker wire has lower resistance. Temperature affects resistance: in metals, resistance increases with temperature as ions vibrate more and impede electron flow.
电阻取决于材料、长度和横截面积。导线越长，电阻越大；导线越粗，电阻越小。温度影响电阻：金属中温度升高，离子振动加剧，阻碍电子流动，电阻增大。
3. Series and Parallel Circuits | 串联与并联电路
In a series circuit, components are connected end-to-end. The current is the same at all points. The total potential difference is shared across the components, and the total resistance is the sum of individual resistances: Rtotal = R₁ + R₂ + ...
在串联电路中，元件首尾相连。各处电流相同。总电压分配给各元件，总电阻为各电阻之和：R总 = R₁ + R₂ + ...
In a parallel circuit, each branch receives the full supply voltage. The total current equals the sum of the branch currents. The total resistance decreases as more branches are added; it is always less than the smallest branch resistance.
在并联电路中，每条支路都承受全部电源电压。总电流等于各支路电流之和。并联支路越多，总电阻越小，且总电阻恒小于最小的支路电阻。
Practical measurements require ammeters connected in series and voltmeters connected in parallel. Domestic lighting and power sockets are wired in parallel so that each appliance operates independently at the same voltage.
实际测量时电流表串联、电压表并联。家庭照明和插座采用并联布线，以便各电器独立工作在同一电压下。
4. Mains Electricity and Power Calculations | 市电与电功率计算
UK mains electricity supplies 230 V alternating current (AC) at 50 Hz. AC means the current repeatedly changes direction. The live wire (brown) carries the alternating potential; the neutral wire (blue) completes the circuit; the earth wire (green/yellow) is a safety wire.
英国市电为 230 V、50 Hz 的交流电 (AC)。交流是指电流方向不断交替变化。火线（棕色）携载交变电势；零线（蓝色）构成回路；地线（绿/黄色）是安全导线。
d is E = P × t, where t is time in seconds. One kilowatt-hour (kWh) equals 3.6 megajoules.
电功率 (P) 是能量转化的速率，单位瓦特 (W)。重要公式：P = I × V 及 P = I² × R。能量转移 E = P × t，其中 t 为秒。1 千瓦时 (kWh) 等于 3.6 兆焦。
Fuses and circuit breakers protect circuits from excessive current. A fuse contains a thin wire that melts if the current exceeds its rating, breaking the circuit. The earth wire and fuse prevent electric shock and fire by providing a low-resistance path to the ground.
保险丝和断路器防止电流过大。保险丝内的细丝在电流超过额定值时熔断，断开电路。地线和保险丝通过提供低阻接地路径防止触电和火灾。
5. Speed, Velocity and Acceleration | 速率、速度与加速度
on. Average speed = total distance ÷ time. Acceleration is the rate of change of velocity:
a = (v - u) / t
速率是标量，表示物体运动的快慢；速度是包含方向的矢量。平均速率 = 总路程 ÷ 时间。加速度是速度的变化率：a = (v - u) / t
Gradients of distance–time graphs give speed. A constant gradient means constant speed; a horizontal line indicates the object is stationary. On velocity–time graphs, the gradient gives acceleration and the area under the graph gives displacement.
路程–时间图像的斜率表示速率。斜率恒定则速率恒定；水平线表示物体静止。在速度–时间图像中，斜率表示加速度，线下面积表示位移。
v, initial velocity u, acceleration a and displacement s. This is useful for analysing motion such as braking distances.
对于匀加速度，公式 v² = u² + 2 a s 将末速度 v、初速度 u、加速度 a 和位移 s 联系起来，常用于分析制动距离等问题。
6. Forces and Newton's Laws of Motion | 力与牛顿运动定律
A force is a push or pull measured in newtons (N). Newton’s first law states that an object remains at rest or moves at constant velocity unless a resultant force acts on it. This describes inertia.
力是推或拉，单位为牛 (N)。牛顿第一定律：若无净外力作用，物体将保持静止或匀速直线运动状态。这描述了惯性。
Newton’s second law links resultant force (F), mass (m) and acceleration (a):
F = m × a
牛顿第二定律将净外力 (F)、质量 (m) 与加速度 (a) 联系起来：F = m × a
Newton’s third law states that whenever two objects interact, they exert equal and opposite forces on each other. These action–reaction pairs act on different bodies.
牛顿第三定律：两个物体相互作用时，彼此施加大小相等、方向相反的力。这对作用力与反作用力作用在不同物体上。
trength (approximately 9.8 N/kg on Earth). Weight differs from mass; mass is the amount of matter in kg.
重力是物体受到的地球引力：W = m × g，g 为引力场强（地球表面约为 9.8 N/kg）。重量不同于质量；质量是物体所含物质的量，单位 kg。
7. Momentum and Car Safety | 动量与汽车安全
. Momentum is a vector quantity. In a closed system, total momentum is conserved, meaning total momentum before a collision equals total momentum after.
动量 (p) 为质量与速度之积：p = m × v，单位为 kg m/s。动量是矢量。在封闭系统中总动量守恒，即碰撞前总动量等于碰撞后总动量。
. This helps explain how safety features such as airbags, seatbelts and crumple zones work – they increase the time over which a collision occurs, reducing the force on occupants.
力等于动量的变化率：F = Δp / t。这有助于解释安全气囊、安全带和溃缩区等安全装置的工作原理——它们延长了碰撞的作用时间，从而减小了乘客所受的力。
Braking and stopping distances increase with speed, adverse weather and driver fatigue. Thinking distance (reaction time) plus braking distance equals stopping distance.
制动距离和停车距离随车速、恶劣天气和疲劳驾驶而增加。思考距离（反应时间行驶的距离）加制动距离等于停车距离。
8. Wave Properties: Reflection and Refraction | 波的性质：反射与折射
Waves transfer energy without transferring matter. In transverse waves (e.g., light, water waves), oscillations are perpendicular to the direction of energy travel. In longitudinal waves (e.g., sound), oscillations are parallel to the energy direction.
波传递能量而不传递物质。横波（如光波、水波）的振动方向与能量传播方向垂直。纵波（如声波）的振动方向与能量传播方向平行。
Key wave quantities: amplitude (maximum displacement from rest), wavelength (λ, distance between consecutive peaks), frequency (f, number of waves per second, Hz) and wave speed (v). The wave equation is:
v = f × λ
波的关键物理量：振幅（偏离平衡位置的最大位移）、波长 (λ, 相邻波峰间的距离)、频率 (f, 每秒波数, Hz) 和波速 (v)。波的方程为：v = f × λ
All waves can be reflected and refracted. Reflection follows the law: angle of incidence equals angle of reflection. Refraction occurs when waves enter a different medium, causing a change in speed and, if they enter at an angle, a change in direction.
所有波都能反射和折射。反射遵循入射角等于反射角的规律。折射发生在波进入不同介质时，波速改变，若斜向入射则传播方向改变。
Sound waves are longitudinal and require a medium. They travel fastest in solids, slower in liquids and slowest in gases. The audible range for humans is approximately 20 Hz to 20 kHz.
声波是纵波，需要介质传播。在固体中最快，液体中次之，气体中最慢。人耳可听范围约 20 Hz 至 20 kHz。
9. Electromagnetic Spectrum and Light | 电磁波谱与光
| Region / 区域 | Wavelength range / 波长范围 | Key uses / 主要用途 |
|---|---|---|
| Radio waves / 无线电波 | ~1 mm to >10 km | Broadcasting, communications / 广播、通信 |
| Microwaves / 微波 | ~1 mm to 30 cm | Wi-Fi, radar, cooking / Wi-Fi、雷达、烹饪 |
| Infrared / 红外线 | 0.7 µm to 1 mm | Thermal imaging, remote controls / 热成像、遥控器 |
| Visible light / 可见光 | 400–700 nm | Vision, photography / 视觉、摄影 |
| Ultraviolet / 紫外线 | 10–400 nm | Fluorescent lamps, sterilization / 荧光灯、消毒 |
| X-rays / X 射线 | 0.01–10 nm | Medical imaging, security / 医学成像、安检 |
| Gamma rays / 伽马射线 | <0.01 nm | Cancer treatment, sterilisation / 癌症治疗、灭菌 |
10⁸ m/s). Their properties differ in wavelength and frequency: higher frequency means shorter wavelength and more energetic radiation.
电磁波谱是一系列横波，在真空中波速相同 (3.0 × 10⁸ m/s)。其性质因波长和频率而异：频率越高，波长越短，辐射能量越高。
Visible light can be dispersed into colours by a prism; red has the longest wavelength and violet the shortest. Beyond visible light, the spectrum extends to invisible radiation with a wide range of practical applications.
可见光可通过棱镜色散为彩色；红光波长最长，紫光最短。可见光之外，波谱延伸至不可见辐射，具有广泛的实际应用。
10. Radioactive Decay and Types of Radiation | 放射性衰变与辐射类型
Some atomic nuclei are unstable and emit radiation to become more stable. This process is radioactive decay. The three main types are alpha (α), beta (β) and gamma (γ) radiation.
某些原子核不稳定，通过放出辐射变得更稳定，这一过程称为放射性衰变。三种主要辐射类型为 α、β 和 γ 射线。
| Property / 性质 | Alpha (α) / 阿尔法 | Beta (β) / 贝塔 | Gamma (γ) / 伽马 |
|---|---|---|---|
| Nature / 本质 | Helium nucleus (2p+2n) / 氦核 | Fast electron / 高速电子 | Electromagnetic wave / 电磁波 |
| Penetration / 穿透力 | Stopped by paper / 纸张可挡 | Stopped by ~3 mm Al / 数毫米铝 | Reduced by thick lead / 厚铅减弱 |
| Ionising power / 电离能力 | Very high / 很强 | Moderate / 中等 | Low / 弱 |
In alpha decay, the mass number decreases by 4 and the atomic number by 2. In beta decay, a neutron turns into a proton and an electron, so the mass number stays the same and the atomic number increases by 1. Gamma emission often accompanies alpha or beta decay and carries away excess energy.
α 衰变中，质量数减 4，原子序数减 2。β 衰变中，一个中子变为一个质子并放出一个电子，质量数不变，原子序数加 1。γ 辐射常伴随 α 或 β 衰变出现，带走多余能量。
11. Half-Life, Background Radiation and Uses | 半衰期、背景辐射与应用
Half-life is the time taken for the number of radioactive nuclei in a sample to halve. It can also refer to the time for the count rate to fall by half. Half-life is constant for a given isotope and is unaffected by temperature or pressure.
半衰期是样品中放射性原子核数目减半所需的时间，也可指计数率下降一半所需的时间。对于给定的同位素，半衰期是常数，不受温度、压力影响。
Radioactive decay is a random process; it is impossible to predict exactly when a particular nucleus will decay. However, with large numbers of nuclei, the decay pattern follows a predictable exponential decline.
放射性衰变是随机过程，无法精确预测某个原子核何时衰变。但当原子核数量庞大时，衰变规律呈现可预测的指数衰减。
Background radiation comes from natural sources (rocks, cosmic rays, radon gas) and artificial sources (medical X-rays, nuclear accidents). Exposure is usually low, but safety protocols require limiting time, increasing distance and using shielding.
背景辐射源自天然（岩石、宇宙射线、氡气）和人工来源（医学 X 光、核事故）。日常照射量较低，但安全规程要求缩短时间、增大距离和使用屏蔽。
Radiation has important uses: alpha sources in smoke detectors, beta for thickness monitoring of paper and foil, gamma for sterilising medical equipment and killing cancer cells. Short half-life isotopes are used as tracers in medicine to minimise radiation dose.
辐射有重要应用：α 源用于烟雾探测器，β 用于纸张/金属箔厚度监测，γ 用于消毒医疗器械和杀死癌细胞。短半衰期同位素用作医学示踪剂以减少辐射剂量。
12. The Universe and Energy Resources | 宇宙与能源资源
The Solar System consists of the Sun, eight planets, moons, asteroids and comets. Planets orbit the Sun in elliptical paths. The force of gravity provides the centripetal force that keeps planets and satellites in orbit.
太阳系由太阳、八大行星、卫星、小行星和彗星组成。行星沿椭圆轨道绕日运行。引力提供向心力，使行星和卫星保持在轨道上。
Redshift of light from distant galaxies shows they are moving away from us. The further a galaxy, the greater its redshift and the faster it recedes. This is evidence for the expanding Universe and supports the Big Bang theory.
遥远星系发出的光发生红移，表明它们正在远离我们。星系越远，红移越大，退行速度越快。这是宇宙膨胀的证据，支持大爆炸理论。
Energy resources are classified as non-renewable (fossil fuels, nuclear) and renewable (solar, wind, wave, tidal, hydroelectric, geothermal, biomass). Fossil fuels release
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