Year 7 Edexcel Physics: High-Frequency Topics & Common Mistakes Analysis | 7年级Edexcel物理：高频考点与易错题分析

📚 Year 7 Edexcel Physics: High-Frequency Topics & Common Mistakes Analysis | 7年级Edexcel物理：高频考点与易错题分析

In Year 7 Edexcel Physics, students are introduced to fundamental concepts that build the foundation for GCSE. Certain topics appear consistently in end-of-year assessments, and many learners lose marks not due to a lack of understanding, but because of recurring misconceptions. This article breaks down the most frequently tested content alongside the typical errors students make, helping you revise smarter and avoid those common pitfalls.

在7年级Edexcel物理课程中，学生开始接触为GCSE打基础的基本概念。一些主题在年终测评中反复出现，而许多学生丢分并非因为不理解，而是由于反复出现的错误认知。本文拆解了最高频的考点以及学生容易犯的典型错误，帮助你更聪明地复习，避开那些常见陷阱。

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

Energy can neither be created nor destroyed – it can only be stored or transferred. In Year 7, you must be able to name the eight energy stores: kinetic, gravitational potential, elastic potential, thermal (internal), chemical, nuclear, magnetic and electrostatic. Energy is transferred mechanically, electrically, by heating or by radiation.

能量既不能被创造也不能被消灭——它只能被储存或转移。在7年级，你必须能够说出八种能量储存方式：动能、重力势能、弹性势能、热能（内能）、化学能、核能、磁能和静电储能。能量通过机械做功、电流、加热或辐射进行转移。

Common mistake: Many students say ‘energy is used up’ or ‘energy disappears’. This is incorrect – energy is always conserved. When a torch runs out, the chemical store in the battery has been transferred to the thermal store of the surroundings and the light energy emitted.

常见错误：很多学生说“能量用光了”或“能量消失了”。这是不正确的——能量总是守恒的。当手电筒没电时，电池中的化学储能被转移到了周围环境的储热中，并以光能的形式发射出去。

Another frequent error is confusing energy stores with energy transfers. For instance, ‘kinetic energy’ is a store, while ‘electrical working’ is a transfer pathway. In exam questions, label what store decreased and what store increased.

另一个常见错误是混淆能量储存和能量转移。例如，“动能”是一种储存，而“电力做功”是一种转移路径。在考试题中，要标明哪种储能减少、哪种储能增加。

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2. Sankey Diagrams and Energy Efficiency | 桑基图与能量效率

Sankey diagrams show energy transfers using arrows, where the width of each arrow represents the amount of energy. The input arrow always splits into useful output and wasted energy. Efficiency is calculated as useful output energy divided by total input energy, often expressed as a percentage.

桑基图用箭头表示能量转移，箭头的宽度代表能量的多少。输入箭头总是分为有用输出和浪费的能量。效率计算为有用的输出能量除以总输入能量，通常以百分比表示。

Common mistake: Drawing Sankey diagrams with equally wide output arrows when the useful and wasted amounts differ. The widths must be proportional. If 300 J of electrical energy powers a lightbulb that produces 60 J of light, the arrow for light must be much narrower than the arrow for heat wasted.

常见错误：在有用和浪费的能量数值不同时，却把桑基图的输出箭头画成等宽。宽度必须成比例。如果300 J的电能点亮灯泡并产生60 J的光能，那么表示光的箭头必须比表示浪费热能的箭头窄得多。

When calculating efficiency, some learners forget to convert answers into percentages or use the wrong formula. Always check: efficiency = useful output ÷ total input. If a hairdryer uses 500 J of electrical energy and gives 150 J of kinetic energy, efficiency = 150 ÷ 500 = 0.3 or 30%.

在计算效率时，一些学习者忘记把答案转换成百分比，或用了错误的公式。一定要检查：效率 = 有用输出 ÷ 总输入。如果一个吹风机消耗500 J电能并产出150 J动能，效率 = 150 ÷ 500 = 0.3 或 30%。

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3. Forces – Balanced and Unbalanced | 力——平衡力与不平衡力

A force is a push or a pull measured in newtons (N). When forces on an object are balanced, the object is either stationary or moving at a constant speed in a straight line. When forces are unbalanced, the object accelerates or decelerates.

力是一种推或拉，单位是牛顿（N）。当作用在一个物体上的力平衡时，该物体要么静止，要么沿直线匀速运动。当力不平衡时，物体会加速或减速。

Common mistake: Believing that a constant forward force is needed to keep something moving at a steady speed. Many students think that if no force is applied, the object stops immediately. In reality, a steady speed requires balanced forces. If a car moves at 20 m/s on a motorway, the driving force equals the resistive forces (friction and air resistance).

常见错误：认为需要持续的向前力才能使物体保持匀速运动。许多学生以为如果不施加力，物体就会立即停止。实际上，匀速运动需要的是平衡力。如果一辆汽车在高速公路上以20 m/s的速度行驶，驱动力等于阻力（摩擦力和空气阻力）。

Another misconception involves free-fall diagrams. When a skydiver reaches terminal velocity, weight and air resistance are balanced. Students often draw arrows of different sizes or say ‘gravity stops acting’. Gravity never stops; the forces simply become equal.

另一个误解涉及自由落体图。当跳伞者达到终极速度时，重力和空气阻力平衡。学生常画出大小不等的箭头，或者说“重力停止起作用了”。重力永远不会停止作用；只是力的大小变得相等而已。

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4. Mass vs Weight | 质量与重量

Mass | 质量	Weight | 重量
Amount of matter in an object | 物体所含物质的多少	Force of gravity pulling on an object’s mass | 重力对物体质量的拉力
Measured in kilograms (kg) | 以千克（kg）为单位	Measured in newtons (N) | 以牛顿（N）为单位
Does not change with location | 不随地点改变	Changes with gravitational field strength | 随引力场强度改变

Common mistake: Using the terms ‘mass’ and ‘weight’ interchangeably in answers. On Earth, the gravitational field strength g is approximately 10 N/kg, so weight = mass × g. A 50 kg student has a weight of 500 N on Earth, but only about 80 N on the Moon. Mass remains 50 kg in both places. Always check your units in calculations.

常见错误：在答案中互换使用“质量”和“重量”。地球的引力场强度 g 约为10 N/kg，因此重量 = 质量 × g。一个50 kg的学生在地球上重500 N，但在月球上只有约80 N。两处的质量都是50 kg。在计算中一定要检查单位。

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5. Speed Calculations and Distance–Time Graphs | 速度计算与距离–时间图

The relationship between speed, distance and time is given by:

speed = distance ÷ time

In Year 7, typical units are metres per second (m/s) or kilometres per hour (km/h). In a distance–time graph, the gradient (slope) indicates the speed. A steeper line means faster movement, a horizontal line means the object is stationary.

速度、距离和时间之间的关系为：速度 = 距离 ÷ 时间。在7年级，常用单位是米每秒（m/s）或千米每小时（km/h）。在距离–时间图中，斜率代表速度。线越陡表示运动越快，水平线表示物体静止。

Common mistake: Confusing the axes. Students sometimes match a flat line on a distance–time graph with ‘constant speed’. A flat line means no change in distance – the object is not moving. Constant speed is shown by a straight, sloping line.

常见错误：混淆坐标轴含义。学生有时将距离–时间图中的水平线理解为“匀速运动”。水平线意味着距离没有变化——物体是静止的。匀速运动表现为一条倾斜的直线。

Another error is failing to convert units before calculating. If a question gives distance in metres and time in minutes, you must convert time to seconds or state the speed in m/min. For example, covering 300 m in 2 minutes: speed = 300 m ÷ 120 s = 2.5 m/s.

另一个错误是计算前没有换算单位。如果题目给出距离以米为单位、时间以分钟为单位，你必须把时间换算成秒，或以米/分钟表示速度。比如，2分钟内行进300米：速度 = 300 m ÷ 120 s = 2.5 m/s。

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6. Electrical Circuits – Current and Voltage | 电路——电流与电压

Current is the flow of electric charge around a circuit and is measured in amperes (amps, A) using an ammeter connected in series. Voltage (potential difference) is the push that drives the current and is measured in volts (V) using a voltmeter connected in parallel across a component.

电流是电荷在电路中的流动，单位为安培（A），用串联的安培计测量。电压（电势差）是驱动电流的推动力，单位为伏特（V），用并联在元件两端的电压表测量。

Common mistake: Thinking that current gets ‘used up’ by components. In a simple series circuit, the current is the same at all points. The brightness of identical bulbs changes only if current splits in a parallel branch. Many students incorrectly predict that the second bulb in series will be dimmer because the first bulb uses some current.

常见错误：认为电流会被元件“用掉”。在简单的串联电路中，电流处处相同。相同灯泡的亮度变化只发生在并联支路中电流分流时。许多学生错误地预测串联中的第二只灯泡会更暗，因为第一只灯泡用掉了一部分电流。

Voltage is often misunderstood. In a series circuit, the voltage supplied by the battery is shared across all components. If two identical bulbs are in series, each receives half the total voltage. In a parallel circuit, each branch receives the full battery voltage. Confusion arises when learners draw ammeters in parallel or voltmeters in series, which would not work.

电压常被误解。在串联电路中，电池提供的电压被所有元件分担。如果两只相同的灯泡串联，每只得到电压的一半。在并联电路中，每条支路都得到全电池电压。当学习者将安培计画成并联、或电压表画成串联时，就会产生混淆，这样连接是无法工作的。

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7. The Particle Model and States of Matter | 粒子模型与物态

The particle model describes solids, liquids and gases in terms of particle arrangement and movement. Solids have particles closely packed in a regular pattern, vibrating in fixed positions. Liquids have particles close together but can move past each other. Gases have particles far apart, moving quickly in random directions.

粒子模型通过粒子的排布和运动来描述固体、液体和气体。固体中粒子紧密排列成规则的结构，在固定位置振动。液体中粒子相互靠近但能彼此滑过。气体中粒子相距很远，朝各个方向快速随机运动。

Common mistake: Drawing particles in liquids as spaced out like a gas or in an irregular pattern but not touching. In the exam, particles in a liquid should be drawn touching, filling the container from the bottom, with no large gaps. Also, students often say particles expand when heated. The particles themselves do not expand; the spaces between them increase.

常见错误：把液体中的粒子画得像气体一样有间距，或者画成不规则形状但没有接触。考试中，液体粒子应画成彼此接触、从底部充满容器、没有大的空隙。此外，学生常说加热时粒子膨胀。粒子本身不会膨胀；是它们之间的空间增大了。

When describing state changes like melting or boiling, some learners forget that temperature stays constant during the change although heating continues. The energy goes into breaking bonds between particles, not raising the temperature. The exam may ask what happens to the energy supplied while a solid melts at its melting point; the answer is it increases the internal energy but temperature remains the same.

在描述熔化或沸腾等状态变化时，有些学生忘记尽管持续加热，温度在变化过程中保持不变。能量用于破坏粒子间的键合，而不是升高温度。考题可能会问当固体在熔点熔化时，所提供的能量发生了什么变化；答案是它增加了内能，但温度保持不变。

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8. Reflection of Light | 光的反射

Light travels in straight lines. When it hits a smooth surface, it reflects obeying the law of reflection: the angle of incidence (i) equals the angle of reflection (r). Both angles are measured from the normal – an imaginary line perpendicular to the surface at the point of incidence.

光沿直线传播。当它遇到光滑表面时会发生反射，遵循反射定律：入射角（i）等于反射角（r）。两个角都从法线量起——法线是在入射点垂直于表面的一条假想线。

Common mistake: Measuring angles from the mirror surface instead of the normal. If a question states that a ray hits a mirror at 30° to the surface, many students mistakenly write the angle of incidence as 30°. The correct angle of incidence is 90° – 30° = 60°. Always draw and label the normal first.

常见错误：从镜面而不是从法线量度角。如果题目说一道光线以与表面成30°角照射到镜面，很多学生错误地将入射角写成30°。正确的入射角是90° – 30° = 60°。一定要先画出并标出法线。

When drawing a ray diagram, some students use dashed lines for incident and reflected rays, or forget to add arrowheads to show direction. Use a solid line for the ray, with an arrow in the middle. The normal should be a dashed line.

在画光路图时，有些学生对入射光线和反射光线使用虚线，或忘记添加箭头来标明方向。针孔光线应使用实线，中间带箭号。法线应该是虚线。

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9. Sound and Wave Properties | 声音与波的性质

Sound is caused by vibrations and travels as a longitudinal wave. It needs a medium (solid, liquid or gas) to travel – it cannot travel through a vacuum. The speed of sound varies with the medium; it travels fastest in solids and slowest in gases.

声音由振动引起，以纵波形式传播。它需要介质（固体、液体或气体）才能传播——不能在真空中传播。声音的速度因介质不同而变化；它在固体中传播最快，在气体中最慢。

Common mistake: Describing sound as moving like a slinky being pushed forwards, confusing wave movement with particle movement. In a longitudinal wave, particles vibrate back and forth parallel to the direction of energy transfer, not travelling from the source to the ear. The sound energy moves, but the air particles stay roughly in the same place.

常见错误：把声音描述成像向前推的弹簧玩具般运动，混淆了波的传播与粒子的运动。在纵波中，粒子沿着与能量传递方向平行的方向前后振动，并非从声源跑到耳朵里。传递的是声能，空气粒子大致停留在原处。

Another common error is stating that sound travels faster in gases because particles are more spread out. The truth is that in gases, particles are far apart and collisions are less frequent, so sound travels slowest. The closer the particles, the faster the vibrations can be passed on, which is why solids generally transmit sound fastest.

另一个常见错误是说声音在气体中传播更快因为粒子更分散。事实是在气体中粒子相距较远，碰撞较不频繁，所以声音传播最慢。粒子越紧密，振动传递得越快，这就是固体通常传声最快的原因。

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10. The Solar System and Orbits | 太阳系与轨道

Our Solar System consists of the Sun, planets, dwarf planets, moons, asteroids and comets. The planets orbit the Sun due to the gravitational force pulling them inward, while their forward motion keeps them from falling in. This balance creates nearly circular orbits.

我们的太阳系由太阳、行星、矮行星、卫星、小行星和彗星组成。行星由于太阳的引力向内拉，同时它们的向前运动使自己不至于掉进去。这种平衡形成了近乎圆形的轨道。

Common mistake: Thinking that planets orbit the Sun because there is ‘no gravity’ in space. Gravity exists everywhere, but it gets weaker with distance. The Sun’s gravitational pull extends far beyond Pluto. Another misconception is that the Sun is the largest star in the universe; it is actually an average-sized star when compared to others.

常见错误：认为行星绕太阳运行是因为太空中“没有重力”。重力无处不在，但随着距离增加而减弱。太阳的引力范围远远超出冥王星。另一种误解是认为太阳是宇宙中最大的恒星；实际上与其他恒星相比，它只是一个中等大小的恒星。

In exam questions about seasons, some students incorrectly link seasons to the Earth being closer to the Sun in summer. Seasons are caused by the tilt of Earth’s axis, not the slight variation in distance. The hemisphere tilted towards the Sun experiences summer, while the opposite hemisphere experiences winter.

在关于季节的考题中，一些学生错误地将季节与夏季地球离太阳更近联系起来。季节是由地轴倾斜引起的，而不是距离的微小变化。朝向太阳倾斜的半球处于夏季，而另一个半球处于冬季。

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11. Density – Practical and Calculation | 密度——实践与计算

Density is a measure of how much mass is packed into a given volume. The formula is:

density = mass ÷ volume

Common units are g/cm³ for solids and liquids, and kg/m³ for larger objects. A regular solid’s volume can be found using length × width × height; an irregular solid’s volume is often found by water displacement.

密度是衡量单位体积内含有多少质量的物理量。公式为：密度 = 质量 ÷ 体积。固体和液体的常用单位是 g/cm³，较大物体可用 kg/m³。规则固体的体积可用长×宽×高求算；不规则固体的体积常用排水法测量。

Common mistake: Students frequently forget to convert grams to kilograms if the volume is in m³, leading to wildly incorrect density values. Also, when using a measuring cylinder for displacement, reading the meniscus incorrectly. Always read at eye level from the bottom of the meniscus and subtract initial volume from final volume to find the object’s volume.

常见错误：学生常常忘记在体积为 m³ 时将克换算为千克，导致密度值完全错误。同时，使用量筒测排水体积时，错误读取弯月面。始终在视线水平处读取弯月面底部，并用最终体积减去初始体积得出物体体积。

Another pitfall is mixing up density with heaviness. An object can be heavy but have a low density if it is very large. A balloon filled with water is heavy but less dense than a small iron nail. Density compares mass and volume, not mass alone.

另一个陷阱是把密度和轻重混淆。一个物体可以很重但如果体积很大则密度很低。一个装满水的气球很重，但密度比一颗小铁钉小。密度比较的是质量和体积，而非仅质量。

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12. Preparing for the Exam – Common Mark-Losing Habits | 备考——常见的失分习惯

Beyond content knowledge, Year 7 students often lose marks through avoidable errors in presentation and command words. Misreading the word ‘explain’ as ‘state’ leads to insufficient detail. When a question asks you to ‘compare’, you must describe both similarities and differences, using connectives like ‘whereas’.

除了学科知识，7年级学生在展示和指令词上常犯可避免的错误而丢分。误把“解释”读成“陈述”会导致细节不足。当题目要求你“比较”时，必须描述相同点和不同点，使用“然而”之类的连接词。

Common mistake: Not showing working in calculations. Even if the final answer is wrong, you can gain marks for correct substitution or rearrangement. Always write down the equation, substitute numbers with units, and give the final answer with the correct unit. Another habit is leaving answers blank; in multiple‑choice or one‑word answers, always attempt a sensible guess.

常见错误：计算题不写步骤。即使最终答案错误，正确的代入或变形也可能得分。务必写出公式，代入数字和单位，并给出带正确单位的最终答案。另一个习惯是留空不答；对于选择题或填空题，总要尝试合理猜测。

Graph plotting is another area where marks vanish. Use a sharp pencil, plot crosses (×) for data points, and draw a single smooth best-fit line. Do not join dots with a ruler if the trend is a curve. Label axes with quantity and unit, and use a clear scale.

绘图是另一个丢分区域。使用削尖的铅笔，用叉号（×）标出数据点，绘制一条平滑的拟合线。如果趋势是曲线，不要用直尺连接点。给坐标轴标上物理量和单位，并使用清晰的比例尺。

Published by TutorHao | Physics Revision Series | aleveler.com

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