📚 Year 7 WJEC Physics: Unit Test Mock Paper Walkthrough | Year 7 WJEC 物理：单元测试模拟卷解析
This mock paper walkthrough is designed to help Year 7 students revise key concepts from the WJEC Physics curriculum. Each question is modeled on typical unit test formats, covering forces, energy, electricity, particles, and waves. Step-by-step explanations are provided in both English and Chinese to support bilingual learners.
这份模拟卷解析旨在帮助 Year 7 学生复习 WJEC 物理课程的核心概念。每道题都参照典型的单元测试格式，涵盖力、能量、电、粒子与波等主题。我们提供中英双语的逐步解析，为双语学习者提供支持。
1. Question 1: Forces on a Stationary Book | 第1题：作用在静止书本上的力
A student places a book on a horizontal desk. The book remains at rest. Which pair of forces correctly describes the forces acting on the book?
一名学生将一本书放在水平桌面上，书本保持静止。下面哪一对力正确地描述了作用在书本上的力？
A. Gravity pulling down and air resistance pushing up
A. 向下的重力和向上的空气阻力
B. Gravity pulling down and friction pushing sideways
B. 向下的重力和侧向的摩擦力
C. Gravity pulling down and normal contact force pushing up
C. 向下的重力和向上的支持力
D. Magnetic force pulling down and tension pulling up
D. 向下的磁力和向上的拉力
The correct answer is C. A book resting on a desk has two main forces acting on it: weight (the pull of gravity) and the normal contact force from the desk pushing upward. These forces are equal in size and opposite in direction, so the book stays still.
正确答案是 C。放在桌面上的书本受到两个主要的力：重力（地球的吸引）和桌面向上的支持力。这两个力大小相等、方向相反，因此书本保持静止。
Air resistance and friction are not significant here because the book is not moving through the air or sliding. Magnetic force and tension are not relevant to this everyday situation. This question tests your understanding of balanced forces and the idea that objects at rest have no net force acting on them.
空气阻力和摩擦力在这里并不明显，因为书本既不在空气中运动也没有滑动。磁力和拉力也与这个日常情景无关。这道题考查的是你对平衡力的理解，即静止的物体所受合力为零。
2. Question 2: Calculating Speed from Distance and Time | 第2题：根据路程和时间计算速度
speed = distance ÷ time to calculate the speed of the cyclist in metres per second (m/s).
一位自行车骑手在 50 秒内骑行了 300 米。请用公式 速度 = 路程 ÷ 时间 计算他的速度，单位是米每秒 (m/s)。
v = s ÷ t
Plugging in the numbers: v = 300 m ÷ 50 s = 6 m/s. The cyclist' s 6 metres per second. This means that each second the cyclist covers 6 metres on average.
代入数值：v = 300 米 ÷ 50 秒 = 6 米/秒。这位骑手的速度是 6 米每秒。也就是说他平均每秒前进 6 米。
When using the equation, always check that the units match: distance in metres and time in seconds give speed in m/s. If the distance were given in kilometres, you would need to convert it to metres first. Year 7 students should also be able to rearrange the formula to find distance or time if speed is known.
使用公式时，务必检查单位：路程用米、时间用秒，得到的速度单位就是米/秒。如果路程以千米给出，你需要先把它换算成米。Year 7 学生还应学会变形公式，在已知速度时求路程或时间。
3. Question 3: Circuit Symbols and Short Circuits | 第3题：电路符号与短路
Look at the circuit diagram below. The cell, two lamps, and a switch are connected with wires. One wire bypasses a lamp. What problem will occur when the switch is closed, and which symbol represents a bulb?
观察下面的电路图。电池、两个灯泡和一个开关用导线连接。其中一根导线绕过了一个灯泡。当开关闭合时会出现什么问题？灯泡的电路符号是哪一种？
The extra wire creates a short circuit across one of the lamps. Current will flow through the path of least resistance – the wire with no lamp – so the lamp that is bypassed will not light up. The other lamp may glow more brightly or burn out because all the current flows through it.
这根额外的导线形成了其中一个灯泡的短路。电流会通过电阻最小的路径——那根没有灯泡的导线，所以被绕过的灯泡不会亮。另一个灯泡可能会变得更亮甚至烧坏，因为所有电流都流过它。
The correct symbol for a lamp (bulb) is a circle with a cross inside. You need to be able to draw and recognise standard circuit symbols for cells, batteries, switches, lamps, and buzzers. A short circuit is dangerous because it can cause overheating and drain the cell quickly.
灯泡的正确符号是一个内部画有十字的圆。你需要能够绘制和识别电池、电池组、开关、灯泡和蜂鸣器的标准电路符号。短路很危险，因为它可能导致过热并迅速耗尽电池。
4. Question 4: Particle Model – Solids, Liquids and Gases | 第4题：粒子模型——固体、液体和气体
Describe the arrangement and movement of particles in a solid, a liquid, and a gas. Use the particle model to explain why solids have a fixed shape but liquids can flow.
请描述固体、液体和气体中粒子的排列和运动方式。利用粒子模型解释为什么固体有固定的形状而液体可以流动。
In a solid, particles are packed closely together in a regular pattern. They vibrate in fixed positions but cannot move around. This gives solids a definite shape and volume.
在固体中，粒子紧密排列成规则的图案。它们在固定的位置上振动但不能自由移动。因此固体有确定的形状和体积。
In a liquid, particles are still close together but are arranged randomly. They can slide past each other, which allows liquids to flow and take the shape of the bottom of a container. Liquids have a fixed volume but no fixed shape.
在液体中，粒子仍然紧密但排列无序。它们可以互相滑动，这使得液体能够流动并呈现容器底部的形状。液体有固定的体积但没有固定的形状。
In a gas, particles are far apart and move randomly at high speed. Gases have no fixed shape or volume; they spread out to fill their container completely.
在气体中，粒子相距很远并快速随机运动。气体没有固定的形状或体积，会扩散并充满整个容器。
5. Question 5: Energy Transfer in a Light Bulb | 第5题：灯泡中的能量转移
A filament light bulb is switched on. What is the main energy transfer pathway? Write down the useful output energy and one form of wasted energy.
一个白炽灯泡被点亮。主要的能量转移路径是什么？写出有用的输出能量和一种被浪费的能量形式。
ransferred. The arrow diagram would be: electrical energy → light energy + thermal energy.
灯泡将电能转化为光能（有用）和热能（浪费）。能量既不会凭空产生也不会凭空消失，只会转移。能量转移的箭头图是：电能 → 光能 + 热能。
In an energy-efficient LED bulb, a much higher proportion of the electrical energy is changed into light, so less is wasted as heat. This is why LEDs are better for saving energy. When answering exam questions, always identify the store of energy at the start and the stores at the end.
在节能的 LED 灯泡中，电能转化为光的比例要高得多，因此以热量形式浪费的能量更少。这就是 LED 更节能的原因。在回答考试问题时，始终要指出起始的能量储存和最终的能量储存。
6. Question 6: Friction – Useful or Unwanted? | 第6题：摩擦力——有用还是有害？
Give one example where friction is useful and one example where friction is unwanted. Explain how friction is reduced in the unwanted case.
请分别举一个摩擦力有用的例子和一个摩擦力有害的例子，并解释在有害的情况下如何减小摩擦力。
Friction is useful when we walk: the friction between our shoes and the ground prevents slipping. Without friction, we could not push off the ground to move forward.
走路时摩擦力是有用的：鞋底与地面的摩擦力防止我们滑倒。没有摩擦力，我们就无法蹬地前行。
Friction is unwanted in bicycle wheel axles or car engines because it slows things down and causes parts to wear out. To reduce unwanted friction, lubricants like oil or grease are used. Smooth, polished surfaces also reduce friction.
摩擦力在自行车轮轴或汽车发动机中是有害的，因为它会减慢运动并导致部件磨损。为了减少有害的摩擦力，会使用油或润滑脂等润滑剂。光滑、抛光的表面也能减小摩擦。
7. Question 7: The Law of Reflection | 第7题：光的反射定律
A ray of light strikes a plane mirror. The angle between the incident ray and the mirror surface is 30°. Draw a diagram and state the angle of reflection. Label the normal, incident ray, and reflected ray.
一束光线射到平面镜上。入射光线与镜面的夹角为 30°。请画图并写出反射角的大小。标出法线、入射光线和反射光线。
The normal is an imaginary line drawn at 90° to the mirror surface. If the ray makes a 30° angle with the mirror, then the angle of incidence (angle between the incident ray and the normal) is 60°. According to the law of reflection, the angle of reflection equals the angle of incidence, so the angle of reflection is also 60°.
法线是一条画在与镜面垂直方向的假想线。如果光线与镜面成 30° 角，那么入射角（入射光线与法线之间的夹角）就是 60°。根据反射定律，反射角等于入射角，因此反射角也是 60°。
Always measure the angle from the normal, not from the mirror surface. The incident ray, reflected ray, and normal all lie in the same plane. This simple rule allows us to predict how light will bounce off smooth surfaces.
一定要从法线开始量角度，而不是从镜面。入射光线、反射光线和法线都在同一平面内。这条简单的规则让我们能够预测光在光滑表面上的反射路径。
8. Question 8: Sound Requires a Medium | 第8题：声音需要介质传播
Explain why astronauts on the Moon cannot hear one another directly, even if they shout loudly. What does this tell you about how sound travels?
解释为什么月球上的宇航员即使大声喊叫也无法直接听到对方的声音。这说明了声音传播的什么特点？
Sound is a vibration that travels through a medium such as air, liquid, or solid. On the Moon, there is no atmosphere – it is a vacuum. Because there are no particles to vibrate, sound cannot travel from one astronaut to another. They have to use radios to communicate.
声音是一种通过介质（如空气、液体或固体）传播的振动。月球上没有大气层——是真空环境。由于没有粒子可以振动，声音无法从一个宇航员传到另一个宇航员。他们必须使用无线电通信。
This demonstrates that sound waves are longitudinal waves that need a material to pass through. Light, however, can travel through a vacuum, which is why we can see the astronauts even though we cannot hear them.
这说明声波是纵波，需要物质才能传播。然而，光可以在真空中传播，这就是为什么我们能看到宇航员却听不到他们说话。
9. Question 9: Calculating Density | 第9题：计算密度
lume of 250 cm³. Calculate its density in g/cm³. Use the formula: density = mass ÷ volume.
一个金属块的质量为 500 克，体积为 250 立方厘米。请以 g/cm³ 为单位计算它的密度。使用公式：密度 = 质量 ÷ 体积。
ρ = m ÷ V
l block is 2 grams per cubic centimetre. This is a typical value for materials like aluminium.
代入数值：ρ = 500 克 ÷ 250 立方厘米 = 2 克/立方厘米。这个金属块的密度是 2 克每立方厘米。这是铝这类材料的典型密度值。
Density tells us how much mass is packed into a given volume. Objects with a density greater than water (1 g/cm³) will sink, while those with a lower density will float. Always remember to include the correct units in your answer.
密度表示单位体积内所含质量的大小。密度大于水（1 g/cm³）的物体将下沉，密度小于水的物体将上浮。答题时务必带上正确的单位。
10. Question 10: Series and Parallel Circuits | 第10题：串联与并联电路
A circuit contains one battery and two identical bulbs. In circuit A, the bulbs are connected in series. In circuit B, the bulbs are connected in parallel. Describe the brightness of the bulbs in each circuit and explain what happens if one bulb is removed.
一个电路包含一个电池组和两个相同的灯泡。电路 A 中灯泡串联；电路 B 中灯泡并联。请描述两种电路中灯泡的亮度，并解释如果取下其中一个灯泡会发生什么。
In a series circuit, the two bulbs share the voltage from the battery, so each bulb is dimmer than it would be alone. If one bulb is removed or blows, the circuit is broken and both bulbs go out – there is no complete path for current.
在串联电路中，两个灯泡共用电池电压，因此每个灯泡都比单独使用时暗。如果取下或烧坏一个灯泡，电路断开，两个灯泡都会熄灭——电流没有完整的回路。
In a parallel circuit, each bulb gets the full battery voltage, so they shine at normal brightness. If one bulb is removed, the other remains on because there is still a complete path for current through the other loop. Parallel circuits are used in home lighting for this reason.
在并联电路中，每个灯泡都获得电池的全部电压，因此以正常亮度发光。如果取下其中一个灯泡，另一个灯泡依然亮着，因为另一条环路仍然有完整的电流通路。正是由于这个原因，家用照明采用并联电路。
Published by TutorHao | Physics Revision Series | aleveler.com
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