📚 Year 7 WJEC Physics: High-Frequency Topics & Common Mistake Analysis | Year 7 WJEC 物理：高频考点与易错题分析
Mastering Year 7 WJEC Physics means understanding both the core concepts and the tricky details that examiners love to test. This article highlights the topics that appear most often in assessments and breaks down the common mistakes students make, helping you sharpen your answers and avoid losing easy marks. Each section pairs an English explanation with Chinese translation, so you can build subject knowledge and bilingual confidence at the same time.
想要稳稳拿下 WJEC Year 7 物理分数，既要吃透核心概念，也要避开那些最容易丢分的陷阱。本文梳理了历年测评中出现频率最高的考点，逐一剖析学生常犯的错误，让你在复习时更有针对性。每个小节均采用英文讲解与中文翻译对照的形式，在巩固物理知识的同时提升双语表达能力。
1. Understanding Forces and Motion | 理解力与运动
A force is a push or a pull that can change an object’s speed, direction or shape. Forces are measured in newtons (N). A very common exam mistake is thinking that a constant force is needed to keep an object moving at a steady speed. In fact, if an object moves at constant velocity, the forces on it are balanced, meaning there is no net force.
力是一种推或拉的作用，可以改变物体的速度、方向或形状。力的单位是牛顿（N）。考试中最常见的错误是认为需要一个持续的力来维持物体的匀速运动。实际上，如果物体做匀速直线运动，说明它受到的力是平衡的，即合力为零。
Another pitfall is confusing “stationary” with “balanced forces”. An object at rest has balanced forces acting on it, but so does an object moving at constant speed in a straight line. Students often draw arrows of different lengths for forces on a car moving at steady speed, which loses marks. Always show pairs of arrows equal in length when motion is not changing.
另一个易错点是把“静止”与“受力平衡”划等号。静止的物体受力平衡，但匀速直线运动的物体受力也是平衡的。很多学生画一辆匀速行驶的汽车时，会把驱动力和阻力箭头画得不一样长，这就会丢分。记住：只要运动状态不变，箭头长度必须相等。
2. Gravity and Weight vs. Mass | 重力与质量的区别
Mass is the amount of matter in an object and is measured in kilograms (kg); it does not change with location. Weight is the force of gravity acting on that mass, measured in newtons (N). The relationship is given by the equation:
质量是物体所含物质的多少，单位是千克（kg），不会随位置变化。重量是作用在该质量上的重力，单位是牛顿（N）。两者之间的关系可用公式表示：
W = m × g
vitational field strength. On Earth, g ≈ 10 N/kg (WJEC often uses 10 N/kg for simplicity).
其中 g 代表引力场强度。在地球表面，g 约等于 10 N/kg（WJEC 试卷为简化计算常取 10 N/kg）。
mistake is using kilograms when the question asks for weight in newtons. If a pupil writes “weight = 5 kg” instead of “weight = 50 N” ing the terms interchangeably. Train yourself to check the unit required before answering.
最常见的错误是题目要求用牛顿表示重量，学生却写了千克。例如一个质量为 5 千克的物体，正确重量应该是 50 牛，写“重量=5 kg”直接没分。还有一个错误是混淆质量和重量，在答题时随意互换。请养成先看题目要求什么单位的习惯。
3. Friction: Helpful and Unhelpful | 摩擦力的利与弊
Friction is a force that opposes motion between two surfaces. It can be useful, such as when it allows car tyres to grip the road, or unhelpful, like when it causes wear on machine parts. Students often forget that friction always acts in the opposite direction to movement (or attempted movement).
摩擦力是一种阻碍两个接触表面相对运动的力。它有时很有用，比如让汽车轮胎抓住路面，有时却带来麻烦，如造成机械零件磨损。学生经常忘记摩擦力的方向永远与运动方向（或运动趋势的方向）相反。
When drawing arrows on a diagram, make sure the friction arrow points backwards relative to the direction the object is moving or about to move. A frequent slip is to draw friction in the same direction as motion, or to only show friction when an object is slowing down. Friction exists whenever surfaces rub together, even at constant speed.
在画力的示意图时，摩擦力的箭头必须指向物体运动方向的反方向。常见的画法错误是把摩擦力画成与运动方向一致，或者只在物体减速时才画摩擦力。事实上，只要两个表面有相对滑动或滑动趋势，摩擦力就存在，哪怕物体做匀速运动也一样。
4. Calculating Speed Correctly | 速度计算与单位换算
Speed is how fast something moves, found by dividing distance by time. The formula is:
速度表示物体运动的快慢，等于距离除以时间，公式为：
average speed = total distance ÷ total time
nge m/s to km/h, multiply by 3.6. To change km/h to m/s, divide by 3.6. For example, 10 m/s = 36 km/h.
WJEC 试题要求答案以米每秒（m/s）或千米每小时（km/h）表示。单位换算是失分重灾区。把 m/s 换成 km/h 要乘以 3.6；把 km/h 换成 m/s 要除以 3.6。例如 10 m/s = 36 km/h。
Pupils also lose marks by mixing up distance and time units, e.g. using metres and minutes in the same calculation without converting minutes to seconds. Always rewrite time in seconds if the distance is in metres. Another common error is using the formula backwards or forgetting to show working, which loses method marks even if the final answer is correct.
学生混淆距离和时间单位也会丢分，比如用米和分钟直接代入公式却不把分钟换算成秒。如果距离单位是米，请先把时间统一为秒。还有两个常见错误：把公式用反了，或者没有写计算过程，即使最终答案正确也拿不到步骤分。
5. Energy Stores and How Energy Moves | 能量的储存与转移
Energy cannot be created or destroyed, only transferred between stores. In Year 7, you are expected to name stores such as kinetic, thermal, chemical, gravitational potential, elastic potential and more, and describe pathways like heating, light, sound or electricity.
能量既不会凭空产生也不会凭空消失，只会从一个能量储存转移到另一个储存。Year 7 要求能够说出动能、热能、化学能、重力势能、弹性势能等储能名称，并描述加热、光、声、电流等转移途径。
A classic exam error is saying “energy disappears” when a ball stops bouncing or a torch is switched off. Instead, you must explain that the energy has been transferred to the surroundings as heat (thermal energy). Also, when drawing energy transfer diagrams, arrows should link stores, not just float. Label each store clearly.
经典错误之一是在皮球停止弹跳或手电筒关闭时说“能量消失了”。正确的说法是能量已经通过热传递散失到了周围环境中。画能量转移图时，箭头必须连接到具体的储能盒上，不能随意飘着，每个储能盒都要清晰地标出名称。
6. Electric Circuits: Series and Parallel | 电路基础：串联与并联
A series circuit has only one loop for current to flow. If one bulb breaks, all bulbs go out. In a parallel circuit, there are multiple paths. If one bulb blows, the others stay on. WJEC frequently asks students to predict bulb brightness when switches are opened or closed.
串联电路只有一条电流回路，一个灯泡坏了，所有灯泡都熄灭。并联电路有多条路径，其中一个灯泡损坏，其余支路仍能工作。WJEC 常要求学生判断开关断开或闭合时灯泡亮度的变化。
Misunderstanding current sharing is a serious mistake. In a series circuit, current is the same everywhere. In a parallel circuit, current splits at junctions, but the total current leaving the battery equals the sum of the branch currents. Many learners think “current gets used up” by bulbs, which is wrong – the current simply flows through and returns to the battery.
对电流分配的理解错误是严重失分点。串联电路中各处电流相等。并联电路中，电流在分支点分流，但流出电池的总电流等于各支路电流之和。不少学生误以为“电流被灯泡消耗掉了”，这是错误的——电流只是流过灯泡，最终回到电池。
7. Measuring Current and Voltage | 电流与电压的测量
An ammeter measures current in amperes (A) and must be connected in series so the current flows through it. A voltmeter measures potential difference in volts (V) and is connected in parallel across the component being tested. Drawing these meters correctly in circuit diagrams is a frequent exam task.
电流表测量电流，单位安培（A），必须串联接入电路让电流流过它。电压表测量电位差，单位伏特（V），必须并联在待测元件两端。在电路图中正确画出这两种电表是经常出现的考题。
A common error is placing the voltmeter in series, which would give a reading but would also prevent the circuit working normally, or putting the ammeter in parallel, which can cause a short circuit and blow a fuse. Make sure the voltmeter has the high-resistance symbol if required, and that you read scales carefully – check whether each small division represents 0.1 V, 0.2 V or 0.5 V.
常见错误是把电压表串联，虽然可能显示读数，但电路无法正常工作；或者把电流表并联，这会造成短路甚至烧坏保险丝。务必确保电压表使用高电阻符号（如果考纲要求），并仔细读刻度——看清楚每一小格代表 0.1 V、0.2 V 还是 0.5 V。
8. Sound Waves: Pitch and Loudness | 声波：音调与响度
Sound is produced by vibrations and travels as a longitudinal wave. It needs a medium; sound cannot travel through a vacuum. The pitch of a sound depends on the frequency of the wave – more waves per second mean a higher pitch. Loudness depends on the amplitude – bigger vibrations produce louder sounds.
声音由振动产生，以纵波的形式传播，需要介质，不能在真空中传播。音调高低由波的频率决定——每秒振动次数越多，音调越高。响度大小取决于振幅——振动幅度越大，声音越响。
Mixing up pitch and loudness is the number one mistake. If a question describes hitting a drum harder, the sound becomes louder (amplitude increases), but the pitch (frequency) stays the same unless the drum’s tension changes. Also, when labelling a waveform, always point the amplitude arrow from the zero line to the crest, and the wavelength arrow from one crest to the next crest, not from crest to trough.
把音调和响度混淆是头号错误。如果题目说“更用力敲鼓”，声音变响（振幅增大），但音调（频率）不变，除非鼓皮的张力发生了变化。另外，在波形图上标注时，振幅箭头必须从零线指向波峰，波长箭头要从一个波峰量到下一个波峰，而不是从波峰量到波谷。
9. The Law of Reflection | 光的反射定律
When light bounces off a smooth surface, the angle of incidence equals the angle of reflection. Both angles are measured from the normal – an imaginary line perpendicular to the surface at the point of incidence. A classic trick in tests is to give the angle between the ray and the mirror, not the angle to the normal.
光在光滑表面发生反射时，入射角等于反射角。这两个角都要从法线量起，法线是过入射点垂直于镜面的一条假想线。考试中一个经典陷阱是给出光线与镜面的夹角，而不是与法线的夹角。
If the question says “a light ray makes an angle of 30° with the mirror”, the angle of incidence is 60° (because 90° – 30° = 60°), not 30°. Students who rush into writing “i = 30°, r = 30°” el it, and show both angles clearly. Use a ruler and protractor for accurate ray diagrams.
如果题目说“一条光线与镜面成 30° 角”，那么入射角应该是 60°（因为 90° – 30° = 60°），而不是 30°。匆忙写下“i = 30°, r = 30°”的同学必然失分。务必用虚线画出法线并标注，清楚标出两个角。画光路图时要用直尺和量角器准确作图。
10. States of Matter and Density | 物态与密度
Particles in solids are tightly packed in a regular pattern, in liquids they are close but can slide past each other, and in gases they are far apart and move quickly. Changes of state, such as melting and boiling, occur at fixed temperatures for a pure substance. Density links mass and volume:
固体粒子紧密排列成规则结构，液体粒子间距略大且可以滑动，气体粒子间距很大且快速运动。纯净物的状态变化如熔化和沸腾发生在固定的温度。密度将质量和体积联系在一起：
density = mass ÷ volume
The most frequent slip is confusing mass with weight again, or using incorrect units. Density is often given in g/cm³ or kg/m³. When calculating density from a practical, students sometimes forget to subtract the mass of the empty container, or they read the volume from the wrong part of the measuring cylinder’s meniscus (always read from the bottom of the curve for water).
最常见的错误还是混淆质量和重量，或者用错单位。密度常用单位是 g/cm³ 或 kg/m³。在实验计算密度时，学生有时忘记先减去空容器的质量，或者量筒读数时看错了液面（水面应该读凹液面的最低点）。
When answering questions about why solids are denser than gases, reference must be made to particles being closer together, not just “more particles”. Two objects can have the same number of particles but different volumes, leading to different densities.
在解释为什么固体密度大于气体时，一定要提到粒子之间的间距更小，而不只是说“粒子更多”。两个物体可以有同样多的粒子，但体积不同，密度也就不同。
11. Graph Skills and Data Handling | 图表技能与数据处理
WJEC tests often include line graphs or bar charts. Make sure the independent variable goes on the x-axis and the dependent variable on the y-axis. Label axes with quantity and unit, use even scales, and plot points with small crosses. Students frequently lose marks by forgetting units on axes, drawing awkward scales, or joining points with a wobbly freehand line instead of using a ruler where appropriate.
WJEC 试题常包含折线图或条形图。一定要把自变量放在 x 轴，因变量放在 y 轴。坐标轴要标出物理量和单位，刻度要均匀，数据点用小的叉号表示。学生常在坐标轴上漏写单位、刻度划分古怪，或者用随手画的波浪线连接数据点（应该使用直尺画直线）而丢分。
When reading values from a graph, double-check the scale before giving your answer. If one small box equals 0.2 units, counting each box as 1 will give wildly wrong readings. Also, describe trends precisely – saying “it goes up” is not as good as “the temperature increases steadily until 100 °C, then remains constant”.
从图表上读取数值时，一定要先确认每个小格代表多少。如果一个小格是 0.2 单位，按 1 计数会得出完全错误的结果。此外，描述变化趋势要准确——“上升了”远不如“温度稳步升高到 100 °C，然后保持不变”来得精准。
In practical-based questions, identify anomalous results and be ready to calculate a mean without including outliers. This is a skill that separates higher-achieving learners from those who simply copy all numbers into a calculator.
在实验题中，要能识别异常数据，并能在计算平均值时剔除异常值。能否做到这一点，往往是高分学生与普通学生的分水岭。
Published by TutorHao | WJEC Physics Revision Series | aleveler.com
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