Year 7 CCEA Physics: Key Knowledge Summary | Year 7 CCEA 物理：核心知识点梳理

📚 Year 7 CCEA Physics: Key Knowledge Summary | Year 7 CCEA 物理：核心知识点梳理

This article provides a clear and concise summary of the core topics covered in Year 7 CCEA Physics. It is designed to help you revise key concepts including forces, energy, electricity, magnetism, matter, waves, space and scientific skills. Each section presents essential knowledge in both English and Chinese to support bilingual learners.

本文清晰简明地总结了Year 7 CCEA物理课程的核心主题，旨在帮助你复习力、能量、电、磁、物质、波、空间和科学探究技能等关键概念。每个部分都以中英双语呈现关键知识，以支持双语学习。

1. Forces and Their Effects | 力及其效应

A force is a push or a pull acting on an object. Forces can change the speed, direction, or shape of an object. The unit of force is the newton (N). We use a force meter (spring balance) to measure force.

力是作用在物体上的推或拉。力可以改变物体的速度、方向或形状。力的单位是牛顿（N）。我们使用测力计（弹簧秤）来测量力的大小。

Contact forces include friction, air resistance, and tension. Non‑contact forces include gravity, magnetic force, and electrostatic force.

接触力包括摩擦力、空气阻力和拉力。非接触力包括重力、磁力和静电力。

Friction is a force that opposes motion between two surfaces in contact. It can be helpful (e.g. grip on tyres) or harmful (e.g. causing wear). Air resistance slows objects moving through air.

摩擦力是阻碍两个接触表面相对运动的力。它可以是有益的（如轮胎的抓地力）或有害的（如导致磨损）。空气阻力会减慢物体在空气中运动的速度。

Gravity is the force of attraction between masses. On Earth, it gives objects weight. Weight is a force measured in newtons, while mass is the amount of matter and is measured in kilograms.

重力是质量间的吸引力。在地球上，重力赋予物体重量。重量是以牛顿为单位测量的力，而质量是物质的多少，以千克为单位测量。

Weight (N) = mass (kg) × gravitational field strength (≈ 10 N/kg on Earth)

重量（N）= 质量（kg） × 重力场强（地球上约为 10 N/kg）

Balanced forces cause no change in motion (object stays at rest or moves at constant speed in a straight line). Unbalanced forces cause an object to accelerate, decelerate, or change direction.

平衡力不会改变物体的运动状态（物体静止或保持匀速直线运动）。非平衡力会使物体加速、减速或改变运动方向。

Forces are represented by arrows in diagrams; the direction shows the direction of the force and the length represents its size.

力在图中用箭头表示；箭头方向表示力的方向，长度表示力的大小。

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2. Energy Types and Transfers | 能量类型与转移

Energy is the ability to do work. It is measured in joules (J). Energy cannot be created or destroyed, only transferred from one form to another or from one place to another. This is the law of conservation of energy.

能量是做功的能力。能量的单位是焦耳（J）。能量不能被创造或毁灭，只能从一种形式转换为另一种形式或从一个地方转移到另一个地方。这就是能量守恒定律。

The main energy types are summarised in the table below:

主要的能量类型总结如下表：

Energy Type	能量类型
Kinetic (movement)	动能（运动的能量）
Gravitational potential (height)	重力势能（由于高度）
Elastic potential (stretched/compressed)	弹性势能（拉伸或压缩）
Thermal (heat)	热能
Chemical (food, fuel, batteries)	化学能（食物、燃料、电池）
Sound	声能
Light	光能
Electrical	电能
Nuclear	核能

Energy can be transferred by forces (doing work), by heating, by electric currents, and by waves (sound and light). For example, a battery converts chemical energy into electrical energy, which then changes into light and thermal energy in a bulb.

能量可以通过力做功、加热、电流以及波（声和光）进行转移。例如，电池将化学能转换为电能，然后在灯泡中转变为光能和热能。

We often draw energy transfer diagrams using boxes and arrows to show how energy moves and changes form. Wasted energy is usually transferred as heat to the surroundings.

我们常用能量转移图表（方框和箭头）来表示能量如何流动和转换。浪费的能量通常以热的形式散失到周围环境中。

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3. Heat Transfer | 热传递

Heat energy moves from a hotter region to a cooler region in three main ways: conduction, convection, and radiation.

热能通过三种主要方式从较热区域传递到较冷区域：传导、对流和辐射。

Conduction occurs mainly in solids. Particles at the hot end vibrate more and pass this vibration to neighbouring particles. Metals are excellent conductors because they have free electrons that move quickly through the material. Insulators (e.g. plastic, wood, air) are poor conductors.

传导主要发生在固体中。热端的粒子振动加剧，并将振动传递给相邻粒子。金属是优良的导体，因为它们拥有能快速移动的自由电子。绝缘体（如塑料、木头、空气）是热的不良导体。

Convection happens in liquids and gases (fluids). When a fluid is heated, it expands, becomes less dense, and rises. Cooler, denser fluid sinks to take its place. This sets up a convection current.

对流发生在液体和气体（流体）中。流体受热后膨胀，密度变小并上升。较冷、密度较大的流体下沉填补空位，由此形成对流循环。

Thermal radiation is the transfer of heat by infrared electromagnetic waves. It does not require particles and can travel through a vacuum. All hot objects emit infrared radiation. Dark, matt surfaces are good absorbers and emitters; shiny, light surfaces are good reflectors.

热辐射是通过红外电磁波传递热量的过程。它不需要粒子，可以在真空中传播。所有热物体都会发出红外辐射。暗色、粗糙的表面是良好的吸收体和发射体；光亮、浅色的表面是良好的反射体。

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4. Simple Circuits and Electricity | 简单电路与电

An electric circuit needs a complete loop (closed circuit) for current to flow. Current is the flow of electric charge (electrons) and is measured in amperes (A) using an ammeter connected in series.

电路需要完整的回路（闭合电路）才能使电流流动。电流是电荷（电子）的流动，用串联的电流表以安培（A）为单位测量。

Voltage (potential difference) provides the ‘push’ that drives the current around the circuit. It is measured in volts (V) using a voltmeter connected in parallel. Resistance opposes the flow of current and is measured in ohms (Ω).

电压（电势差）提供推动电荷在电路中流动的“推力”，其单位为伏特（V），用并联的电压表测量。电阻阻碍电流的流动，单位为欧姆（Ω）。

Common circuit components and their symbols: a cell (battery), a switch, a bulb (lamp), a buzzer, a motor, and connecting wires. In a series circuit, all components are connected one after another; the current is the same everywhere. Adding more bulbs in series makes them dimmer because resistance increases.

常见电路元件及其符号：电池（组）、开关、灯泡、蜂鸣器、马达和导线。在串联电路中，所有元件依次连接；电路中各处电流相等。串联增加灯泡会使它们变暗，因为总电阻增大了。

Conductors such as metals allow electricity to pass through easily because they have free electrons. Insulators such as rubber and plastic do not allow current to flow. A short circuit happens when current finds a very low‑resistance path, which can be dangerous and cause overheating.

导体如金属能让电流轻易通过，因为它们有自由电子。绝缘体如橡胶和塑料不允许电流通过。短路发生在电流找到一条电阻极低的路径时，这很危险，可能导致过热。

Safety rules: never touch electrical appliances with wet hands, keep water away from circuits, and always turn off the power before making changes.

安全守则：切勿用湿手触摸电器，让电路远离水，在改动电路前务必切断电源。

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5. Magnetism | 磁性

A magnet has two poles: a north‑seeking pole (N) and a south‑seeking pole (S). Like poles repel each other; opposite poles attract. A compass is a tiny magnet that aligns with Earth’s magnetic field.

磁铁有两极：指北极（N）和指南极（S）。同极相斥，异极相吸。指南针是一个能沿地球磁场方向排列的小磁针。

The region around a magnet where magnetic forces act is called the magnetic field. Field lines point from the north pole to the south pole. The field is strongest near the poles, where the lines are closest together.

磁铁周围磁力作用的区域称为磁场。磁感线从北极指向南极。磁场在两极附近最强，那里磁感线最密集。

An electromagnet is made by wrapping a coil of wire around an iron core and passing an electric current through it. The magnetic field is only present when current flows. The strength of an electromagnet can be increased by: increasing the current, adding more turns of wire in the coil, and using a soft iron core.

电磁铁是通过在铁芯上缠绕线圈并通入电流制成的。只有在通电时才会产生磁场。可以通过以下方法增强电磁铁的磁性：增大电流、增加线圈匝数以及使用软铁芯。

Uses of electromagnets include electric bells, relays, scrap‑metal lifting cranes, and loudspeakers. They are useful because they can be switched on and off.

电磁铁的应用包括电铃、继电器、废铁起重机和扬声器。它们之所以实用，是因为可以方便地开关。

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6. States of Matter and the Particle Model | 物质的状态与粒子模型

All matter is made up of tiny particles (atoms or molecules). The properties of solids, liquids, and gases can be explained by how these particles are arranged and how they move.

所有物质都由微小粒子（原子或分子）构成。固体、液体和气体的性质可以通过粒子的排列方式和运动方式来解释。

In a solid, particles are packed closely in a regular pattern, held

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