📚 Year 7 CCEA Physics: Core Concepts Overview | Year 7 CCEA 物理：核心知识点梳理
Welcome to your Year 7 CCEA Physics revision guide. Physics explains how the universe behaves — from tiny particles to huge galaxies. This article summarises the key concepts you will meet in your first year, covering forces, energy, electricity, magnetism, waves and space. Each section is designed to help you understand the ‘big ideas’ and prepare for tests.
欢迎来到 Year 7 CCEA 物理复习指南。物理解释了宇宙的运作方式——从微小的粒子到巨大的星系。这篇文章梳理了你第一年将会遇到的核心概念，包括力、能量、电学、磁学、波和太空。每一部分都旨在帮助你理解”大观念”并为考试做好准备。
1. What is Physics? | 什么是物理学？
Physics is the study of matter, energy and the interactions between them. In Year 7, you will explore how forces change motion, why objects fall, how electricity flows, what makes sounds loud or quiet, and how the Earth moves in space. Being curious and asking ‘why’ is the first step to thinking like a physicist.
物理学是研究物质、能量及其相互作用的学科。在七年级，你将探索力如何改变运动、为什么物体会下落、电流如何流动、什么使得声音响亮或轻柔，以及地球如何在太空中运动。保持好奇心并问”为什么”是像物理学家一样思考的第一步。
2. Forces: Pushes and Pulls | 力：推和拉
A force is a push or a pull. Forces can change an object’s speed, direction or shape. We measure forces in newtons (N), using a force meter. A force is a vector quantity — it has both size (magnitude) and direction. Arrows can represent forces; the longer the arrow, the bigger the force.
力是推或拉。力可以改变物体的速度、方向或形状。我们用力计测量力，单位是牛顿 (N)。力是矢量——它具有大小和方向。箭头可以表示力；箭头越长，力越大。
When forces on an object are balanced, the object stays still or moves at a steady speed. Unbalanced forces cause acceleration, deceleration or a change in direction. Friction is a force that opposes motion and often produces heat.
当物体所受的力平衡时，物体保持静止或匀速运动。不平衡的力会导致加速、减速或方向改变。摩擦力是阻碍运动的力，常常产生热量。
3. Gravity, Mass and Weight | 重力、质量与重量
Gravity is a non-contact force that pulls objects towards each other. On Earth, gravity pulls everything towards the centre of the planet. Mass is the amount of matter in an object, measured in kilograms (kg). Weight is the force of gravity on an object and is measured in newtons (N).
重力是一种把物体拉向彼此的非接触力。在地球上，重力把一切拉向地心。质量是物体所含物质的多少，用于克 (kg) 衡量。重量是作用在物体上的重力，用牛顿 (N) 衡量。
weight = mass × gravitational field strength
W = m × g, where g ≈ 10 N/kg on Earth
重量 = 质量 × 重力场强度
W = m × g, 地球上的 g ≈ 10 N/kg
Your mass stays the same everywhere, but your weight changes on different planets because the gravitational field strength changes. For example, the Moon’s gravity is about 1.6 N/kg, so you would weigh much less there.
你的质量在任何地方都保持不变，但重量在不同星球上会改变，因为重力场强度不同。例如，月球的重力场强度约为 1.6 N/kg，所以你在那里会轻得多。
4. Energy: Types and Transfers | 能量：类型与转化
Energy is the ability to do work. It comes in different forms: kinetic (movement), thermal (heat), light, sound, electrical, chemical, nuclear, gravitational potential and elastic potential. The unit of energy is the joule (J).
能量是做功的能力。它有不同形式：动能（运动）、热能（热）、光能、声能、电能、化学能、核能、重力势能和弹性势能。能量的单位是焦耳 (J)。
The law of conservation of energy states that energy cannot be created or destroyed, only transferred from one form to another. For example, when a torch is switched on, chemical energy in the battery → electrical energy → light energy + thermal energy.
能量守恒定律指出，能量不能凭空产生或消灭，只能从一种形式转化为另一种形式。例如，手电筒打开时，电池的化学能 → 电能 → 光能 + 热能。
5. Renewable and Non-renewable Energy | 可再生与不可再生能源
Non-renewable resources are finite and will eventually run out. They include fossil fuels (coal, oil, natural gas) and nuclear fuels. Burning fossil fuels releases carbon dioxide and contributes to climate change.
不可再生资源储量有限，最终会耗尽。它们包括化石燃料（煤、石油、天然气）和核燃料。燃烧化石燃料会释放二氧化碳，加剧气候变化。
Renewable resources can be replenished naturally. Examples are solar, wind, wave, tidal, hydroelectric, geothermal and biomass. These sources produce little or no greenhouse gases during operation, but they can depend on weather and location.
可再生资源可以自然补给。例子有太阳能、风能、波浪能、潮汐能、水力发电、地热和生物质。这些能源在使用过程中产生很少或不产生温室气体，但可能取决于天气和地理位置。
6. Electric Circuits | 电路
An electric circuit is a closed loop that allows current to flow. It needs a power source (cell or battery), wires and a component such as a bulb or buzzer. We draw circuits using standard symbols for each component.
电路是允许电流流动的闭合回路。它需要电源（电池或电池组）、导线和如灯泡或蜂鸣器这样的元件。我们用标准符号绘制电路图。
Current is the flow of electric charge, measured in amperes (A) using an ammeter. In a simple series circuit, the current is the same everywhere. If a switch is open, the circuit is incomplete and no current flows.
电流是电荷的流动，用电流表测量，单位是安培 (A)。在简单的串联电路中，各处电流相同。如果开关断开，电路不完整，没有电流流动。
7. Conductors and Insulators | 导体与绝缘体
Materials that allow electric current to pass through easily are called conductors. Most metals like copper, aluminium and iron are good conductors because they have free electrons that can move. Graphite (a form of carbon) is also a conductor.
容易让电流通过的材料叫作导体。大多数金属如铜、铝和铁是良导体，因为它们有可以自由移动的电子。石墨（碳的一种形式）也是导体。
Insulators are materials that do not let current flow through them. Plastic, rubber, glass and dry wood are good insulators. Insulators are used to coat wires and to keep us safe from electric shocks.
绝缘体是不允许电流通过的材料。塑料、橡胶、玻璃和干木材是良好的绝缘体。绝缘体用于包裹导线，保护我们免受电击。
8. Magnetism | 磁学
A magnet has two poles: north (N) and south (S). Like poles repel each other; unlike poles attract. The magnetic field is the area around a magnet where magnetic forces act. Field lines point from north to south and are closest together where the field is strongest.
磁铁有两个极：北极 (N) 和南极 (S)。同极相斥；异极相吸。磁场是磁铁周围磁力作用的区域。磁感线从北极指向南极，在磁场最强的地方最密集。
The Earth acts like a giant bar magnet, and a compass needle points to magnetic north. An electromagnet is made by winding a coil of wire around an iron core and passing a current through it. Electromagnets can be turned on and off and are used in scrapyard cranes and electric bells.
地球就像一个巨大的条形磁铁，指南针指向磁北极。电磁铁由绕在铁芯上的线圈通以电流制成。电磁铁可以开关，用于废料场起重机、电铃等。
9. Sound and Hearing | 声音与听觉
Sound is produced when an object vibrates back and forth. These vibrations travel through a medium (solid, liquid or gas) as a longitudinal wave. Sound cannot travel through a vacuum because there are no particles to carry the vibration.
物体来回振动时产生声音。这些振动通过介质（固体、液体或气体）以纵波的形式传播。声音无法在真空中传播，因为没有粒子承载振动。
The pitch of a sound depends on its frequency — how many vibrations per second, measured in hertz (Hz). High-frequency sounds have a high pitch. The loudness depends on the amplitude of the wave; bigger vibrations make louder sounds. Our ear has an eardrum that vibrates when sound waves hit it.
声音的音调取决于它的频率——每秒钟振动的次数，单位是赫兹 (Hz)。高频率的声音音调高。响度取决于波的振幅；振幅越大声音越响。我们的耳朵有鼓膜，在声波撞击时振动。
10. Light and Seeing | 光与视觉
Light is a form of energy that travels in straight lines. We see objects because light reflects off them and enters our eyes. A shadow forms when an opaque object blocks the light path.
光是沿直线传播的能量形式。我们看到物体是因为光从物体表面反射进入我们的眼睛。当不透明物体挡住光路时，就会形成影子。
The law of reflection states: angle of incidence = angle of reflection. Both angles are measured from the normal, an imaginary line at 90° to the surface. A plane mirror forms a virtual image that is upright and the same size as the object, but laterally inverted (left and right are swapped).
反射定律表明：入射角 = 反射角。这两个角都是从法线（一条与表面成 90° 的假想线）测量。平面镜形成正立、等大的虚像，但左右颠倒。
White light can be split into the colours of the rainbow (red, orange, yellow, green, blue, indigo, violet) using a prism. This is called dispersion. The colour we see depends on which wavelengths of light are reflected.
白光可以通过棱镜分解成彩虹的颜色（红、橙、黄、绿、蓝、靛、紫），这叫作色散。我们看到的颜色取决于哪些波长的光被反射。
11. The Solar System and Earth’s Movements | 太阳系与地球的运动
Our Solar System contains the Sun, eight planets, dwarf planets, moons, asteroids and comets. The four inner rocky planets are Mercury, Venus, Earth and Mars. The four outer gas giants are Jupiter, Saturn, Uranus and Neptune. Earth orbits (revolves around) the Sun once every 365.25 days, causing years and seasons.
我们的太阳系包含太阳、八大行星、矮行星、卫星、小行星和彗星。四颗内岩质行星是水星、金星、地球和火星。四颗外气态巨行星是木星、土星、天王星和海王星。地球每 365.25 天围绕太阳公转一圈，产生年和季节。
Earth rotates on its tilted axis once every 24 hours, which gives us day and night. The side facing the Sun experiences day, while the opposite side is in night. The tilt of the axis, combined with the orbit, causes the seasons: when the Northern Hemisphere tilts towards the Sun, it is summer there.
地球每 24 小时绕其倾斜的地轴自转一圈，带来白天和黑夜。面向太阳的一面是白昼，背面则是黑夜。地轴的倾斜结合公转产生了季节：当北半球倾向太阳时，那里是夏天。
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