GCSE Physics: Last-Minute Revision Notes | GCSE 物理：考前冲刺笔记

📚 GCSE Physics: Last-Minute Revision Notes | GCSE 物理：考前冲刺笔记

This set of notes covers the essential knowledge, key equations, and common pitfalls for GCSE Physics. Use it as a rapid refresher in the final days before your exam to consolidate core concepts across Energy, Electricity, Particle Model, Atomic Structure, Forces, Waves, Magnetism, Space Physics, and more.

这套笔记涵盖了 GCSE 物理的重要知识、关键方程和常见陷阱。在考前最后几天用它快速回顾，巩固能量、电学、粒子模型、原子结构、力、波、磁学、空间物理等核心概念。

1. Energy Stores and Transfers | 能量储存与转移

Energy is a conserved quantity; it can be stored in different ways and transferred between stores, but never created or destroyed.

能量是一个守恒量；它可以以不同方式储存，并在储存之间转移，但绝不会被创造或消灭。

nergy (Eₑ) for a stretched spring: Eₑ = ½ k e², where k is the spring constant and e is the extension.

动能 (Eₖ) 是物体运动的能量：Eₖ = ½ m v²。重力势能 (Eₚ) 取决于高度：Eₚ = m g h。弹性势能 (Eₑ) 对于拉伸弹簧：Eₑ = ½ k e²，其中 k 为弹簧常数，e 为伸长量。

hen a force moves an object. Power is the rate of energy transfer: P = E ÷ t or P = W ÷ t.

做功 (W) 是能量转移的量度：当力移动物体时 W = F d。功率是能量转移的速率：P = E ÷ t 或 P = W ÷ t。

Efficiency = (useful output energy ÷ total input energy) × 100%. No device is 100% efficient; some energy is always dissipated, often as thermal energy.

效率 = (有用输出能量 ÷ 总输入能量) × 100%。没有设备能达到 100% 效率；总会有能量耗散，通常以热能形式散失。

Conduction, convection and radiation are the main heat transfer processes. Reducing unwanted energy transfers (insulation, lubrication) increases efficiency.

传导、对流和辐射是主要的热传递方式。减少不必要的能量转移（隔热、润滑）可提高效率。

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2. Electricity | 电学

d loop, current is the same everywhere. In a parallel circuit, current splits at junctions.

电流 (I) 是电荷流动的速率：I = Q ÷ t。在单一闭合回路中，各处电流相等。在并联电路中，电流在节点处分流。

: V = E ÷ Q. The sum of p.d.s across components in a series circuit equals the source p.d.

电势差（电压，V）是每单位电荷转移的能量：V = E ÷ Q。串联电路中各元件两端电势差之和等于电源电势差。

I is directly proportional to V at constant temperature. Resistance increases with temperature in a filament lamp.

电阻 (R) 是电势差与电流之比：V = I R。对于定值电阻，温度恒定时 I 与 V 成正比。白炽灯丝电阻随温度升高而增大。

Components can be ohmic (straight-line I-V graph) or non-ohmic (diode, filament). The resistance of an LDR decreases with light intensity; a thermistor's resistance decreases with temperature rise.

元件可以是欧姆的（I-V 图为直线）或非欧姆的（二极管、灯丝）。光敏电阻 (LDR) 的电阻随光照强度增加而减小；热敏电阻的电阻随温度升高而减小。

lel: 1/Rₜₒₜₐₗ = 1/R₁ + 1/R₂ + ... . Adding resistors in parallel reduces total resistance.

串联：R_total = R₁ + R₂ + ... 。并联：1/R_total = 1/R₁ + 1/R₂ + ... 。并联电阻会降低总电阻。

er: P = I V, P = I² R, P = V² ÷ R. Energy transferred: E = P t, also E = I V t or E = Q V.

电功率：P = I V，P = I² R，P = V² ÷ R。电能量：E = P t，或者 E = I V t，E = Q V。

National Grid uses step-up transformers to increase voltage and reduce current, minimising thermal losses; step-down transformers lower voltage for safe domestic use.

国家电网使用升压变压器提高电压、降低电流，以减少热损耗；再通过降压变压器将电压降至家用安全水平。

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3. Particle Model of Matter | 物质粒子模型

nsity ρ = m ÷ V, measured in kg/m³. An object floats if its density is less than the fluid's density.

密度 ρ = m ÷ V，单位 kg/m³。物体密度小于流体密度时会漂浮。

Internal energy is the sum of kinetic and potential energies of particles. Heating increases internal energy; a change of state occurs without a temperature change.

内能是粒子动能和势能的总和。加热可增加内能；物态变化时温度不变。

oiling): E = m L. Specific heat capacity: ΔE = m c Δθ, where Δθ is the temperature change.

熔化和汽化的比潜热：E = m L。比热容：ΔE = m c Δθ，其中 Δθ 为温度变化。

reasing temperature raises average kinetic energy and pressure (at constant volume). Boyle's Law: for a fixed mass of gas at constant temperature, p V = constant, or p ∝ 1/V.

气体压强由粒子撞击容器壁引起。温度升高（体积不变）会增加平均动能和压强。玻意耳定律：一定质量气体在恒温下，p V = 常数，或 p ∝ 1/V。

Doing work on a gas (e.g., compressing it quickly) can increase its temperature without heating.

对气体做功（例如快速压缩）可以在不加热的情况下使其温度升高。

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4. Atomic Structure and Radioactivity | 原子结构与放射性

ns + neutrons. Isotopes have the same number of protons but different numbers of neutrons.

原子由原子核（质子+中子）和束缚在能级上的电子组成。质子数 = 原子序数；核子数 = 质子数 + 中子数。同位素质子数相同但中子数不同。

Radioactive decay is random. Alpha (α) particles: ⁴₂He nuclei, strongly ionising, stopped by paper or a few cm of air. Beta (β⁻) particles: fast electrons, moderately ionising, stopped by a few mm of aluminium. Gamma (γ) rays: electromagnetic waves, weakly ionising, reduced by thick lead or concrete.

放射性衰变是随机的。α 粒子：⁴₂He 核，电离能力强，能被纸或几厘米空气阻挡。β⁻ 粒子：高速电子，中等电离能力，几毫米铝板可阻挡。γ 射线：电磁波，电离能力弱，厚铅板或混凝土可减弱。

→ ²¹⁰₈₂Pb + ⁴₂He (α decay). Half-life is the time for half the nuclei in a sample to decay – it is constant for a given isotope.

核反应方程须平衡质量数和电荷数：²¹⁴₈₄Po → ²¹⁰₈₂Pb + ⁴₂He (α 衰变)。半衰期是样品中一半原子核衰变所需的时间——对给定同位素是常数。

Irradiation is exposure to radiation; contamination is when radioactive material gets onto or into an object. Background radiation comes from rocks, cosmic rays, and medical sources.

辐射照射是指暴露于辐射；污染是指放射性物质附着或进入物体。本底辐射来源于岩石、宇宙射线和医疗源。

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5. Forces and Motion | 力与运动

Scalars have magnitude only (speed, distance, mass); vectors have magnitude and direction (velocity, displacement, force). Resultant force is the single force that has the same effect as all forces acting.

标量只有大小（速率、路程、质量）；矢量既有大小又有方向（速度、位移、力）。合力是与所有作用的力效果相同的单一力。

Newton' here F is the resultant force. Third law: action and reaction forces are equal and opposite, acting on different bodies.

牛顿第一定律：物体若不受合力作用，则保持静止或匀速直线运动。第二定律：F = m a，其中 F 为合力。第三定律：作用力与反作用力大小相等、方向相反，作用在不同物体上。

arth. Friction opposes motion. Terminal velocity occurs when weight equals air resistance.

重量 W = m g；地球上 g ≈ 9.8 N/kg。摩擦力阻碍运动。当重力等于空气阻力时到达终端速度。

tum before a collision or explosion equals total momentum after. Ft = m v − m u (impulse).

动量 p = m v。封闭系统中，碰撞或爆炸前后总动量守恒。冲量 Ft = m v − m u。

a t², v² = u² + 2 a s. Braking distance increases with speed, mass, and reduced friction.

匀加速运动方程：v = u + a t，s = u t + ½ a t²，v² = u² + 2 a s。刹车距离随速度、质量和摩擦力减小而增加。

kwise moments = total anticlockwise moments. Levers and gears transmit rotational effects.

力矩：M = F d (力到支点的垂直距离)。平衡时，顺时针总力矩等于逆时针总力矩。杠杆和齿轮传递转动效果。

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6. Waves | 波

Waves transfer energy without transferring matter. Transverse waves (e.g., light, water waves): oscillations perpendicular to direction of energy transfer. Longitudinal waves (e.g., sound): oscillations parallel to direction of energy transfer.

波传递能量而不传递物质。横波（如光波、水波）：振动方向与能量传递方向垂直。纵波（如声波）：振动方向与能量传递方向平行。

Wave speed: v = f λ. Period T = 1/f. Frequency is measured in hertz (Hz).

波速：v = f λ。周期 T = 1/f。频率单位为赫兹 (Hz)。

on occurs when a wave changes speed at a boundary, causing a change in direction unless incident along the normal.

反射遵循定律：入射角等于反射角。折射发生在波在不同介质边界速度改变时，导致方向变化，除非入射沿法线。

ed, visible, ultraviolet, X-ray, gamma. All travel at 3 × 10⁸ m/s in a vacuum. Uses: radio – communication; microwaves – cooking, satellite; infrared – thermal imaging; visible – seeing; UV – tanning, sterilisation; X-rays – medical imaging; gamma – cancer treatment.

电磁波谱按频率递增/波长递减排列：无线电波、微波、红外线、可见光、紫外线、X 射线、伽马射线。真空中波速均为 3 × 10⁸ m/s。用途：无线电——通信；微波——烹饪、卫星；红外——热成像；可见光——视觉；紫外线——晒黑、消毒；X 射线——医学成像；伽马射线——癌症治疗。

Sound waves are longitudinal and cannot travel through a vacuum. Pitch is determined by frequency; loudness by amplitude. Ultrasound has frequency above 20 kHz and is used for sonar and medical scanning.

声波是纵波，不能在真空中传播。音调由频率决定；响度由振幅决定。超声波频率高于 20 kHz，用于声呐和医学扫描。

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7. Magnetism and Electromagnetism | 磁与电磁

Permanent magnets have north and south poles; like poles repel, unlike attract. Magnetic field lines point from north to south and show direction of force on a north pole.

永磁体有南北极；同名相斥，异名相吸。磁感线从北极指向南极，表示北极所受磁力的方向。

A current-carrying wire produces a circular magnetic field (right-hand grip rule). An electromagnet is a solenoid with an iron core – its strength increases with current, number of turns, and the presence of a soft iron core.

载流导线产生环形磁场（右手握线定则）。电磁铁是带铁芯的螺线管——其强度随电流、线圈匝数和软铁芯的增加而增强。

otor effect: a current-carrying conductor in a magnetic field experiences a force. Fleming' (N to S), second finger = current (+ to −). Force F = B I L (field perpendicular to wire).

电动机效应：磁场中的载流导线受到力的作用。弗莱明左手定则给出方向：拇指——力，食指——磁场 (N→S)，中指——电流 (+→−)。力 F = B I L（磁场与导线垂直）。

Generator effect: moving a wire in a magnetic field or changing the magnetic field around a coil induces a potential difference. This is electromagnetic induction. The induced p.d. can be increased by stronger magnet, faster motion, or more turns.

发电机效应：导线在磁场中运动或改变线圈周围的磁场会感应出电势差。这是电磁感应。增强磁铁、加快运动或增加匝数可提高感应电势差。

Iₚ Vₚ = Iₛ Vₛ. A step-up transformer has more turns on secondary coil, increasing voltage.

变压器改变交流电压：Vₚ / Vₛ = Nₚ / Nₛ。对于理想变压器，输入功率 = 输出功率：Iₚ Vₚ = Iₛ Vₛ。升压变压器次级线圈匝数更多，可升高电压。

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8. Space Physics | 空间物理

Our Solar System contains the Sun (a star), eight planets, dwarf planets, moons, asteroids and comets. Gravity provides the centripetal force keeping planets and satellites in orbit.

我们的太阳系包含太阳（一颗恒星）、八大行星、矮行星、卫星、小行星和彗星。引力提供向心力，使行星和卫星维持在轨道上。

More massive stars become red supergiants and end in a supernova, leaving a neutron star or black hole.

类似太阳的恒星生命周期：星云 → 原恒星 → 主序星（氢聚变为氦）→ 红巨星 → 行星状星云 → 白矮星。更重的恒星会变成红超巨星，最终超新星爆发，留下中子星或黑洞。

Red-shift: light from distant galaxies is shifted towards the red end of the spectrum, indicating they are moving away. More distant galaxies show greater red-shift, meaning the Universe is expanding. This supports the Big Bang theory.

红移：远星系的光谱向红端移动，表明它们在远离。更远的星系红移更大，证明宇宙正在膨胀。这支持大爆炸理论。

Evidence for the Big Bang includes cosmic microwave background radiation (CMBR) and the observed helium abundance. The Universe is about 13.8 billion years old.

大爆炸的证据包括宇宙微波背景辐射 (CMBR) 和观测到的氦丰度。宇宙年龄约 138 亿年。

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9. Key Equations Recap | 关键方程回顾

Memorising these equations is vital for solving numerical problems. Use the correct units and convert where necessary.

记住这些方程对解决数值问题至关重要。使用正确单位，必要时进行换算。

Quantity	Equation	Symbols & Units
Speed	v = s ÷ t	v (m/s), s (m), t (s)
Acceleration	a = Δv ÷ t	a (m/s²), Δv (m/s), t (s)
Weight	W = m g	W (N), m (kg), g (N/kg)
Force (Newton's 2nd)	F = m a	F (N), m (kg), a (m/s²)
Moment	M = F d	M (Nm), F (N), d (m)
Kinetic energy	Eₖ = ½ m v²	Eₖ (J), m (kg), v (m/s)
G.P.E.	Eₚ = m g h	Eₚ (J), m (kg), g (N/kg), h (m)
Elastic potential	Eₑ = ½ k e²	Eₑ (J), k (N/m), e (m)
Work done	W = F d	W (J), F (N), d (m)
Power	P = E ÷ t	P (W), E (J), t (s)
Efficiency	Efficiency = useful output ÷ total input	(ratio or %)
Charge	Q = I t	Q (C), I (A), t (s)
Ohm's law	V = I R	V (V), I (A), R (Ω)
Electrical power	P = I V = I² R = V²/R	P (W), I (A), V (V), R (Ω)
Wave speed	v = f λ	v (m/s), f (Hz), λ (m)
Density	ρ = m ÷ V	ρ (kg/m³), m (kg), V (m³)
Specific latent heat	E = m L	E (J), m (kg), L (J/kg)
Transformer turns	Vₚ / Vₛ = Nₚ / Nₛ	V (V), N (turns)

Many equations are provided on a formula sheet, but you must know how to use them.

许多方程会提供在公式表上，但你必须知道如何使用它们。

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10. Exam Tips and Common Misconceptions | 应试技巧与常见误区

Always show your working and state the equation first, substitute values, then calculate.

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