📚 Year 7 OCR Physics: Core Knowledge Summary | 核心知识点梳理
Year 7 OCR Physics introduces the fundamental ideas that explain how our universe behaves, from why a ball falls to the ground to how a light bulb glows. This revision guide summarises every key topic you need to master: energy stores and transfers, forces and motion, electricity, waves, the solar system and the particle model of matter. Read through the paired English–Chinese explanations, use the tables and diagrams, and you will build a rock‑solid foundation for the rest of your physics journey.
Year 7 OCR 物理课程带你走进解释世界运转的基本概念，从球为什么会落地到灯泡为什么会发光。这篇复习指南总结了所有必须掌握的核心主题：能量储存与传递、力与运动、电学、波、太阳系以及物质的粒子模型。跟着中英对照的讲解、表格和示意图，你将为未来的物理学习打下坚实的基础。
1. Energy Stores and Transfers | 能量储存与传递
Energy is the ability to do work. It is never created or destroyed, only transferred from one store to another. The main energy stores you need to know are: kinetic energy (energy of moving objects), gravitational potential energy (energy due to an object's height), elastic potential energy (energy stored in stretched or compressed springs), thermal energy (heat), chemical energy (stored in fuels, food and batteries), and nuclear energy (stored inside atoms).
能量是做功的能力。它既不会凭空产生也不会凭空消失，只能从一个储存库转移到另一个储存库。你需要知道的主要能量储存形式有：动能（运动物体的能量）、重力势能（因物体高度而具有的能量）、弹性势能（储存在拉伸或压缩弹簧中的能量）、热能（热量）、化学能（储存在燃料、食物和电池中）以及核能（储存在原子内部）。
Energy can be transferred between stores by four pathways: mechanically (by a force doing work), by heating (due to a temperature difference), by radiation (light or sound waves), and electrically (when a current flows). For example, when you lift a book, chemical energy in your muscles is transferred mechanically into gravitational potential energy of the book. In all changes, the total amount of energy in a closed system stays constant – this is the principle of conservation of energy.
能量可以通过四种途径在储存库之间传递：机械做功（通过力做功）、加热（因温差）、辐射（光或声波）以及电学途径（电流流动）。例如，当你举起一本书时，你肌肉中的化学能通过机械做功转移为书的重力势能。在任何变化中，一个封闭系统的总能量保持不变——这就是能量守恒定律。
| Energy Store | Description |
|---|---|
| Kinetic | Energy of a moving object |
| Gravitational potential | Energy stored because of height in a gravitational field |
| Elastic potential | Energy stored when an object is stretched or squashed |
| Thermal | Energy transferred from a hotter object to a colder one |
| Chemical | Energy stored in bonds between atoms, released in reactions |
能量储存形式对照：动能、重力势能、弹性势能、热能和化学能。
2. Forces and Motion | 力与运动
A force is a push or a pull that can change the speed, direction or shape of an object. Force is measured in newtons (N), named after Sir Isaac Newton. Forces can be contact forces, where two objects must touch (friction, air resistance, tension), or non‑contact forces, where objects do not need to be touching (gravity, magnetism, electrostatic force).
力是一种推或拉，能够改变物体的速度、方向或形状。力的单位是牛顿（N），以艾萨克·牛顿爵士命名。力可以分为接触力（两物体必须接触，如摩擦力、空气阻力、张力）和非接触力（物体无需接触，如重力、磁力、静电力）。
To describe movement, we use the idea of speed. Speed tells us how fast an object moves and is calculated by dividing the distance travelled by the time taken. If an object covers 100 metres in 20 seconds, its speed is 5 metres per second (m/s). A distance–time graph can show whether an object is stationary, moving at constant speed, or accelerating.
我们使用速度来描述运动。速度告诉我们物体移动的快慢，计算公式为：运动距离除以所用时间。如果一个物体在20秒内移动了100米，它的速度就是5米每秒（m/s）。距离–时间图可以表示物体是静止、匀速运动还是加速运动。
speed = distance ÷ time
- Average speed ignores changes during a journey; instantaneous speed is the speed at a particular moment.
平均速度忽略行程中的变化；瞬时速度是某一特定时刻的速度。
3. Gravity and Weight | 重力与重量
Gravity is a non‑contact force that attracts any two objects with mass. The larger the mass, the stronger the pull. On the surface of the Earth, the gravitational field strength (g) is approximately 10 N/kg (more precisely 9.8 N/kg). Every kilogram of mass experiences a downward pull of 10 N.
重力是一种非接触力，吸引任何有质量的两个物体。质量越大，引力越强。在地球表面，重力场强度（g）大约为10 N/kg（更精确为9.8 N/kg）。每千克质量受到10 N的向下拉力。
Weight is the force caused by gravity acting on a mass. It is not the same as mass. Mass is the amount of matter in an object and is measured in kilograms (kg); it stays the same wherever you are. Weight can change depending on the gravitational field strength – an astronaut weighs less on the Moon because g is about 1.6 N/kg there. The equation linking weight, mass and g is:
重量是重力作用在质量上产生的力。它不同于质量。质量是物体所含物质的多少，以千克（kg）为单位；无论你在哪里，质量都保持不变。重量会因重力场强度而变化——宇航员在月球上的重量更轻，因为那里的g大约为1.6 N/kg。联系重量、质量和g的公式为：
weight (N) = mass (kg) × gravitational field strength (N/kg)
Be careful: mass is measured with a balance; weight is measured with a force meter (spring balance).
注意：质量用天平测量；重量用测力计（弹簧秤）测量。
4. Balanced and Unbalanced Forces | 平衡与不平衡力
When several forces act on an object, we can replace them by a single resultant force. If the forces are balanced – equal in size and opposite in direction – the resultant force is zero. An object with balanced forces remains at rest or continues to move at a constant speed in a straight line. This is Newton's First Law of Motion.
当几个力作用在一个物体上时，我们可以用一个合力来替代它们。如果力是平衡的——大小相等、方向相反——合力为零。受平衡力的物体将保持静止或沿直线匀速运动。这就是牛顿第一运动定律。
If the forces are unbalanced, there is a non‑zero resultant force. This causes the object to accelerate (change its velocity). Acceleration can mean speeding up, slowing down, or changing direction. Friction and air resistance often act to oppose motion; when a skydiver reaches a speed where air resistance equals their weight, the forces become balanced and they fall at a constant terminal velocity.
如果力不平衡，就会存在一个非零的合力。这将导致物体加速（改变速度）。加速可以指速度增加、减小或改变方向。摩擦力和空气阻力通常会阻碍运动；当跳伞者达到一个空气阻力等于其重量的速度时，力达到平衡，他们将以恒定的终端速度下落。
- Balanced forces → constant velocity or at rest.
- Balanced forces → 匀速或静止。
- Unbalanced forces → acceleration in the direction of the resultant force.
- Unbalanced forces → 沿合力方向加速。
5. Electric Circuits | 电路
An electric circuit is a complete loop of conductive material that allows electric charge to flow continuously. Every circuit must have an energy source (cell or battery), a load (such as a lamp, motor or buzzer), and connecting wires made of metal. If there is a break anywhere in the loop, current stops – this is an open circuit.
电路是一个由导电材料组成的完整回路，允许电荷持续流动。每个电路必须有一个电源（电池）、一个负载（如灯泡、马达或蜂鸣器）以及金属导线。如果回路中任何地方断开，电流就会停止——这就是断路。
There are two basic ways to connect components. In a series circuit, everything is connected one after another in a single path; the current is the same at every point. In a parallel circuit, there are several paths (branches); the current splits up and recombines. Household lighting is wired in parallel so that if one bulb fails, the others stay on. Standard circuit symbols help us draw clear circuit diagrams: a cell is shown as two lines (one long, one short), a battery as several cells, a lamp as a circle with a cross, and a switch as a break in the line.
连接元件有两种基本方式。在串联电路中，所有元件一个接一个地连接，形成单一路径；各处电流相同。在并联电路中，有多条路径（支路）；电流会分流并再次汇合。家庭照明采用并联接线，这样即使一个灯泡坏了，其他灯泡仍然亮着。标准的电路符号帮助我们画出清晰的电路图：电池用一长一短两条线表示，电池组用多组线条，灯泡用一个带叉的圆圈表示，开关用断开的线条表示。
6. Current and Voltage | 电流与电压
Electric current is the rate of flow of electric charge, measured in amperes (A). You can imagine current as the amount of charge passing a point each second. In a series circuit, the current is the same everywhere because there is only one path. In a parallel circuit, the total current from the battery is equal to the sum of the currents in the individual branches.
电流是电荷流动的速率，以安培（A）为单位。你可以把电流想象成每秒钟通过某点的电荷量。在串联电路中，由于只有一条路径，各处电流相同。在并联电路中，电池提供的总电流等于各支路电流之和。
Voltage (or potential difference) tells us how much energy is transferred to or from each unit of charge, measured in volts (V). A battery provides a 'push' that makes charges move. In a series circuit, the supply voltage is shared across all the components; each component uses a part of the energy. In a parallel circuit, each branch receives the full supply voltage. Some Year 7 courses also introduce the relationship between voltage, current and resistance, known as Ohm's law:
电压（电势差）告诉我们每单位电荷转移了多少能量，以伏特（V）为单位。电池提供了一个“推动力”，使电荷移动。在串联电路中，电源电压由各个元件分担；每个元件消耗一部分能量。在并联电路中，每个支路都获得全部电源电压。部分 Year 7 课程也会介绍电压、电流和电阻之间的关系，即欧姆定律：
voltage (V) = current (A) × resistance (Ω)
In a simple circuit, a larger resistance means a smaller current if the voltage stays the same.
在简单电路中，如果电压不变，电阻越大则电流越小。
7. Sound Waves | 声波
Sound is produced when an object vibrates. These vibrations make the particles of the surrounding medium (air, liquid or solid) compress and expand, creating a longitudinal wave. In a longitudinal wave, the vibrations are parallel to the direction the wave travels. Sound cannot travel through a vacuum because there are no particles to vibrate.
声音是由物体振动产生的。这些振动使周围介质（空气、液体或固体）的粒子发生压缩和膨胀，形成纵波。在纵波中，振动方向与波的传播方向平行。声音不能在真空中传播，因为那里没有粒子可以振动。
The frequency of a sound wave determines its pitch: a high frequency means a high‑pitched sound (like a whistle), and a low frequency means a low‑pitched sound (like a drum). Frequency is measured in hertz (Hz), where 1 Hz is one vibration per second. The amplitude of the wave determines its loudness; a larger amplitude transfers more energy and sounds louder. Most humans can hear frequencies from about 20 Hz to 20 000 Hz, although this range shrinks with age.
声波的频率决定其音调：频率高则音调高（如哨声），频率低则音调低（如鼓声）。频率以赫兹（Hz）为单位，1 Hz 表示每秒振动一次。波的振幅决定其响度；振幅越大，传递的能量越多，声音越响。大多数人类可以听到大约20 Hz到20 000 Hz的频率，尽管这个范围会随年龄增长而缩小。
8. Light and Seeing | 光与视觉
Light is a form of electromagnetic radiation that travels in straight lines at extremely high speed (about 300 000 km/s in a vacuum). When light strikes a surface, it can be reflected, transmitted or absorbed. Smooth, shiny surfaces like mirrors reflect light regularly; rough surfaces scatter light, which is why we do not see clear reflections on a wall.
光是一种电磁辐射，沿直线以极高的速度传播（真空中约300 000 km/s）。当光照射到表面时，可以被反射、透射或吸收。光滑、闪亮的表面（如镜子）发生规则反射；粗糙表面会散射光，这就是为什么我们在墙上看不到清晰影像的原因。
The law of reflection says that the angle of incidence (the angle between the incoming ray and the normal) is equal to the angle of reflection (the angle between the outgoing ray and the normal). The normal is a dashed line drawn perpendicular to the surface at the point of contact. Refraction occurs when light passes from one transparent material to another, e.g. from air to glass. The light changes speed and usually bends, making a straw in water look broken. White light can be split into a spectrum of seven colours (red, orange, yellow, green, blue, indigo, violet) by a prism – this is called dispersion. We see non‑luminous objects because they reflect light into our eyes; the colour we see is the colour that is reflected while the others are absorbed.
反射定律指出，入射角（入射光线与法线之间的夹角）等于反射角（反射光线与法线之间的夹角）。法线是在入射点垂直于表面的一条虚线。当光从一种透明材料进入另一种时，例如从空气进入玻璃，会发生折射。光的速度改变，通常会发生弯曲，使水中的吸管看起来像折断了一样。白光通过棱镜可以被分解为七种颜色的光谱（红、橙、黄、绿、蓝、靛、紫）——这称为色散。我们看到不发光的物体是因为它们将光反射入我们的眼睛；我们看到的颜色是物体反射的颜色，其他颜色被吸收了。
angle of incidence = angle of reflection
9. The Solar System | 太阳系
Our solar system is made up of the Sun, eight planets, their moons, dwarf planets, asteroids and comets. The four inner planets (Mercury, Venus, Earth, Mars) are small and rocky. The four outer planets (Jupiter, Saturn, Uranus, Neptune) are much larger and made mainly of gas and ice. Between Mars and Jupiter lies the asteroid belt. The Sun is a star – a huge ball of glowing gas that produces light and heat through nuclear fusion.
我们的太阳系由太阳、八大行星、它们的卫星、矮行星、小行星和彗星组成。四颗内行星（水星、金星、地球、火星）体积小、由岩石构成。四颗外行星（木星、土星、
Published by TutorHao | Year 7 Physics Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图