📚 Year 8 AQA Physics: Core Knowledge Summary | Year 8 AQA 物理：核心知识点梳理
This article provides a comprehensive overview of the key topics covered in Year 8 AQA Physics. It is designed to help students consolidate their understanding of forces, energy, electricity, magnetism and waves. Each section pairs essential explanations in English with equivalent Chinese text to support bilingual learning.
本文全面梳理了 Year 8 AQA 物理课程的核心知识点，旨在帮助学生巩固力、能量、电、磁和波等重点内容。每个小节均提供中英双语对应解释，助力双语学习。
1. Speed and Distance‑Time Graphs | 速度与距离‑时间图
Speed tells us how fast an object is moving. It is calculated by dividing the distance travelled by the time taken.
速度表示物体运动的快慢。它通过物体移动的距离除以所用的时间来计算。
v = d ÷ t
The standard unit of speed is metres per second (m/s). Other common units include kilometres per hour (km/h) and miles per hour (mph).
速度的标准单位是米每秒（m/s）。其他常用的单位还有千米每小时（km/h）和英里每小时（mph）。
A distance‑time graph plots distance on the vertical axis against time on the horizontal axis. The slope (gradient) of the line represents the object’s speed.
距离‑时间图的纵轴为距离，横轴为时间。图上直线的斜率（坡度）表示物体的速度。
- A straight, sloping line means constant speed. A steeper slope means a higher speed.
- 一条倾斜的直线表示匀速运动。斜率越大，速度越快。
- A horizontal line means the object is stationary (zero speed).
- 水平线表示物体静止（速度为零）。
- A curved line indicates that the speed is changing – the object is accelerating or decelerating.
- 曲线表示速度在变化——物体在加速或减速。
To find the speed from a distance‑time graph, pick two points on the straight part of the line and calculate the change in distance divided by the change in time.
从距离‑时间图上求速度时，在直线的部分选择两点，用距离的变化量除以时间的变化量。
2. Gravity, Weight and Mass | 重力、重量和质量
Mass is the amount of matter in an object and is measured in kilograms (kg). It does not change with location.
质量是物体所含物质的多少，单位是千克（kg）。质量不随位置而改变。
Weight is the force of gravity acting on an object. It is measured in newtons (N) and depends on the gravitational field strength.
重量是作用在物体上的重力，单位是牛顿（N），它取决于引力场强度。
W = m × g
On Earth, the gravitational field strength g is approximately 10 N/kg (more precisely 9.8 N/kg). On the Moon, g is only about 1.6 N/kg, so an object weighs much less than on Earth, even though its mass remains the same.
地球上的引力场强度 g 约等于 10 N/kg（更精确为 9.8 N/kg）。月球上的 g 只有大约 1.6 N/kg，因此同一个物体在月球上的重量远小于地球上，但其质量保持不变。
Weight always acts towards the centre of the planet and can be measured with a spring balance (newtonmeter).
重力的方向总是指向地心，可以用弹簧测力计（牛顿计）来测量。
3. Pressure in Solids and Fluids | 固体和流体中的压力
Pressure is a measure of how concentrated a force is. It is calculated with the equation:
压力是表示力集中程度的物理量。计算公式为：
P = F ÷ A
where P is pressure in pascals (Pa), F is force in newtons (N), and A is area in square metres (m²). One pascal is equal to one newton per square metre.
式中 P 表示压力，单位是帕斯卡（Pa），F 是力（N），A 是面积（m²）。1 Pa 等于 1 N/m²。
A sharp knife has a very small area, so the pressure exerted is high, making it easy to cut. Snowshoes have a large area, which spreads the force and reduces pressure, preventing sinking into snow.
锋利的刀口面积很小，产生的压力很大，因此更容易切割。雪地靴的面积很大，分散了力，从而减小压力，避免陷入雪中。
In a liquid or gas, pressure acts in all directions and increases with depth. The pressure in a liquid is given by:
在液体或气体中，压力向各个方向作用，并随深度增加而增大。液体中的压强公式为：
P = h × ρ × g
where h is depth, ρ is the density of the liquid, and g is gravitational field strength.
其中 h 是深度，ρ 是液体密度，g 是引力场强度。
4. Series and Parallel Circuits | 串联与并联电路
A series circuit has only one path for the current to flow. If one component breaks, the whole circuit stops working. The current is the same everywhere in a series circuit.
串联电路只有一条电流路径。若某个元件断开，整个电路便停止工作。串联电路中各处的电流大小都相等。
In a parallel circuit, there are two or more branches. The current splits between the branches, but the voltage across each branch is the same. If one branch is broken, the others can still work.
并联电路有两条或更多支路。电流在各支路间分配，但每条支路两端的电压相等。如果某条支路断开，其他支路仍可正常工作。
Household lighting circuits are wired in parallel so that each lamp receives the full mains voltage and can operate independently. Series circuits are sometimes used in simple torches or fairy lights, where a single broken bulb breaks the circuit.
家庭照明电路采用并联方式，这样每个灯泡都能得到完整的电源电压并独立工作。简单的电筒或小彩灯有时使用串联，当一个灯泡损坏时整个电路断开。
| Feature | Series | Parallel |
| Path for current | One single path | Multiple branches |
| Current | Same at all points | Splits between branches |
| Voltage | Shared between components | Same across each branch |
| Effect of one break | All go out | Other branches still work |
5. Current, Voltage and Resistance | 电流、电压和电阻
Electric current is the flow of electric charge. It is measured in amperes (A) using an ammeter connected in series. In a metal wire, current is the movement of free electrons.
电流是电荷的定向移动。电流表需串联在电路中测量，单位是安培（A）。在金属导线中，电流是自由电子的移动。
Voltage (potential difference) is the energy transferred per unit of charge. It is measured in volts (V) with a voltmeter connected in parallel across a component. Voltage can be thought of as the ‘push’ that drives current through a circuit.
电压（电势差）是单位电荷转移的能量。电压表需并联在元件两端，单位是伏特（V）。电压可以理解为推动电流流过电路的“推力”。
Resistance tells us how difficult it is for current to flow. It is measured in ohms (Ω). A longer or thinner wire has higher resistance. Resistance can be calculated using Ohm’s law:
电阻表示电流通过的难易程度，单位是欧姆（Ω）。导线越长或越细，电阻越大。电阻可通过欧姆定律计算：
R = V ÷ I
where R is resistance, V is voltage, and I is current. For a fixed resistor, current is directly proportional to voltage.
式中 R 为电阻，V 为电压，I 为电流。对于固定电阻器，电流与电压成正比。
If resistance is high, the current is low for a given voltage. Components like lamps and diodes do not obey Ohm’s law because their resistance changes with temperature or applied voltage.
在电压一定的情况下，电阻越大，电流越小。灯泡和二极管等元件不遵循欧姆定律，因为它们的电阻随温度或所加电压而变化。
6. Magnetism and Electromagnets | 磁学与电磁铁
A magnet has two poles – north (N) and south (S). Like poles repel each other; unlike poles attract. Permanent magnets are made of materials such as iron, steel, cobalt and nickel, and always produce a magnetic field.
磁铁有两个磁极——北极（N）和南极（S）。同名磁极相互排斥，异名磁极相互吸引。永磁体由铁、钢、钴、镍等材料制成，始终产生磁场。
An electromagnet is made by wrapping a coil of wire around an iron core and passing an electric current through the coil. The magnetic field can be switched on and off by controlling the current.
电磁铁由绕在铁芯上的线圈通入电流制成。通过控制电流，可以方便地接通或断开磁场。
The strength of an electromagnet can be increased by:
以下方法可以增强电磁铁的磁性：
- increasing the current in the coil
- 增大线圈中的电流
- adding more turns to the coil
- 增加线圈的匝数
- using a soft iron core instead of air
- 使用软铁芯代替空气芯
Electromagnets are used in scrapyard cranes, electric bells, relays and loudspeakers because their magnetism can be controlled and is very strong when needed.
电磁铁用于废料场起重机、电铃、继电器和扬声器等设备，因为其磁力易于控制且在需要时非常强。
7. Work, Energy and Power | 功、能量和功率
‘Work’ is done when a force moves an object in the direction of the force. Work is a way of transferring energy from one store to another.
当力使物体沿力的方向移动时，我们就说做了“功”。功是将能量从一个储存库转移到另一个储存库的一种方式。
W = F × d
where W is work in joules (J), F is force in newtons (N), and d is distance moved in metres (m). Lifting a book vertically or dragging a box across the floor both involve doing work.
式中 W 是功（J），F 是力（N），d 是沿力方向移动的距离（m）。将书本竖直提起或在地板上拖动箱子，都涉及做功。
Power is the rate at which work is done or energy is transferred. It is measured in watts (W). One watt means one joule of energy transferred per second.
功率是做功或能量转移的快慢。单位是瓦特（W）。1 瓦特表示每秒钟转移 1 焦耳的能量。
P = W ÷ t
More powerful appliances transfer energy faster. A 100 W light bulb transfers 100 J of electrical energy into light and heat every second.
功率越大的电器能量转移越快。一个 100 W 的灯泡每秒钟将 100 J 的电能转化为光能和热能。
8. Energy Stores and Transfers | 能量储存与转移
Energy can be stored in different ways: kinetic energy (moving objects), gravitational potential energy (objects raised above the ground), elastic potential energy (stretched or compressed springs), chemical energy (fuels, food, batteries), thermal energy (hot objects), nuclear energy and electrostatic energy.
能量可以储存在多种形式中：动能（运动的物体）、重力势能（被举高的物体）、弹性势能（被拉伸或压缩的弹簧）、化学能（燃料、食物、电池）、热能（高温物体）、核能和静电能。
Energy is transferred between stores by four main pathways: mechanically (by a force doing work), electrically (by an electric current), by heating (temperature difference) and by radiation (e.g. light and sound waves).
能量通过四种主要途径在储存库之间转移：机械做功（力做功）、电途径（电流）、加热（温差）和辐射（如光波和声波）。
The principle of conservation of energy states that energy cannot be created or destroyed, only transferred from one store to another or dissipated (spread out) to the surroundings, usually as thermal energy.
能量守恒定律指出，能量既不能被创造也不能被消灭，只能从一个储存库转移到另一个储存库，或耗散（散失）到周围环境中，通常以热能的形式。
Energy transfer diagrams and Sankey diagrams are used to visualise how much energy is usefully transferred and how much is wasted. Reducing unwanted energy transfers improves efficiency.
能量转移图和桑基图用于可视化多少能量被有效利用，多少被浪费。减少不必要的能量转移可以提高效率。
9. Heating and Thermal Energy Transfer | 加热与热能传递
Thermal energy (heat) always moves from a hotter object to a cooler one until both reach the same temperature. This transfer can happen in three ways:
热能（热量）总是从高温物体向低温物体传递，直到两者温度相同。传递方式有三种：
- Conduction – mainly in solids, where vibrating particles pass energy to neighbouring particles. Metals are good conductors because they have free electrons that move quickly through the material.
- 热传导——主要发生在固体中，振动的粒子将能量传递给邻近的粒子。金属是良导体，因为它们含有能快速移动的自由电子。
- Convection – in liquids and gases, where warmer, less dense fluid rises and cooler, denser fluid sinks, creating a convection current.
- 热对流——发生在液体和气体中，温度较高、密度较小的流体上升，温度较低、密度较大的流体下沉，形成对流循环。
- Radiation – transfer of energy by infrared electromagnetic waves. All hot objects emit infrared radiation; no particles are needed, so it can travel through a vacuum.
- 热辐射——通过红外电磁波传递能量。所有热物体都会发射红外辐射；不需要粒子，因此可以在真空中传播。
Insulation reduces unwanted heat transfers. Examples include double‑glazed windows (trapped air is a poor conductor), loft insulation and wearing layers of clothing.
隔热措施可以减少不必要的热传递。例如双层玻璃窗（密封的空气是热的不良导体）、屋顶隔热层和多层衣物。
10. Sound Waves and Light Waves | 声波与光波
Sound is a longitudinal wave caused by vibrating particles. It travels fastest in solids, slower in liquids and slowest in gases because it needs particles to pass on the vibrations. Sound cannot travel through a vacuum.
声音是由粒子振动产生的纵波。声波在固体中传播最快，液体中次之，气体中最慢，因为它需要粒子传递振动。声音不能在真空中传播。
The loudness of a sound depends on the amplitude of the wave: a larger amplitude produces a louder sound. The pitch depends on the frequency: a higher frequency gives a higher pitch.
声音的响度取决于波的振幅：振幅越大，声音越响。音调取决于频率：频率越高，音调越高。
Light is a transverse wave and does not need particles to travel, so it can move through a vacuum. It travels in straight lines at a speed of about 300,000 km/s in empty space.
光是一种横波，传播不需要介质，因此可以在真空中传播。光在真空中沿直线传播，速度约为 30 万 km/s。
ion. These angles are measured from the normal, an imaginary line perpendicular to the surface.
光的反射遵循定律：入射角等于反射角。这些角是从法线（垂直于表面的假想线）开始测量的。
White light can be split into the colours of the visible spectrum (red, orange, yellow, green, blue, indigo, violet) by a prism or water droplets, forming a rainbow. This is called dispersion.
白光通过棱镜或水滴可以被分解为可见光谱的颜色（红、橙、黄、绿、蓝、靛、紫），形成彩虹，这称为色散。
Published by TutorHao | Physics Revision Series | aleveler.com
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