📚 Experimental Investigations in the Complete Physics for Cambridge Secondary 1 Workbook | 《剑桥初中物理练习册》实验探究
Experimental investigations lie at the heart of the Cambridge Secondary 1 Physics curriculum. Through hands-on practical work, students not only verify scientific principles but also develop essential skills such as planning, observing, measuring, recording, and evaluating. The ‘Complete Physics for Cambridge Secondary 1 Workbook’ provides a rich source of investigations that guide learners in understanding how science works. This article offers a comprehensive overview of the key experimental skills and inquiry approaches covered in the workbook, with detailed examples and practical tips to help students excel in laboratory work and prepare for further studies.
实验探究是剑桥初中物理课程的核心。通过动手实践，学生不仅验证科学原理，还可培养规划、观察、测量、记录和评估等核心技能。《剑桥初中物理练习册》提供了丰富的探究活动，引导学生理解科学方法。本文全面梳理了练习册中涉及的实验探究技能与方法，并通过详细示例与实用技巧，帮助学生提升实验能力，为后续学习做好准备。
1. The Role of Experiments in Physics Learning | 实验在物理学习中的作用
Physics is an experimental science. Every law and principle we study originates from careful observation and measurement. In the Cambridge Secondary 1 course, experiments help students move from concrete experiences to abstract thinking, making concepts such as forces, energy and waves more tangible.
物理是一门实验科学。我们所学的每一条定律和原理都源于细致的观察与测量。在剑桥初中课程中，实验帮助学习者从具体体验过渡到抽象思维，使力、能量和波等概念变得更加直观。
By conducting investigations, students learn to ask questions, predict outcomes, manipulate apparatus, and analyse data. These process skills are just as important as knowing the correct answers. The workbook emphasises the ‘how’ of science, encouraging learners to think like a scientist.
通过开展探究活动，学生学会提出问题、预测结果、操作仪器和分析数据。这些过程技能与获取正确答案同样重要。练习册强调科学的“方法”，鼓励学生像科学家一样思考。
Furthermore, experimental work develops patience, attention to detail, and the ability to work safely in a team. These attributes are valuable far beyond the physics laboratory.
此外，实验工作能够培养耐心、对细节的关注以及团队合作的安全操作能力，这些品质的价值远远超越了物理实验室的范畴。
2. Identifying Variables | 识别变量
Every fair investigation rests on a clear understanding of variables. The independent variable is the one you deliberately change, the dependent variable is the one you measure, and the control variables are all the other factors that must be kept constant.
每一次公平的探究都建立在对变量的清晰理解之上。自变量是你主动改变的那个量，因变量是你测量的结果，而控制变量是所有必须保持不变的其他因素。
For example, when investigating how the length of a pendulum affects its period, the length is the independent variable, the period is the dependent variable, and the mass of the bob and the angle of release should be controlled. The workbook provides many scenarios where students must identify these variables before starting the practical.
例如，在探究单摆的长度如何影响其周期时，摆长是自变量，周期是因变量，摆球的质量和释放角度则是需要控制的变量。练习册提供了大量情境，要求学生在开始实验前就必须识别这些变量。
Only by controlling all other variables can we be confident that any change in the dependent variable is caused by the independent variable. This is the essence of a fair test, a concept repeatedly reinforced in Cambridge Secondary Physics.
只有控制了所有其他变量，我们才能确信因变量的变化确实是由自变量引起的。这就是公平测试的本质，也是剑桥初中物理中不断强化的概念。
3. Formulating a Hypothesis | 提出假设
A hypothesis is a testable prediction, often written as ‘If … then … because …’. It links the independent and dependent variables with a scientific reason. In the workbook, students are frequently asked to state a hypothesis before planning their experiments.
假设是一个可检验的预测，常写作“如果……那么……因为……”。它将自变量和因变量与科学理由联系起来。在练习册中，学生经常被要求在规划实验前先陈述假设。
For instance, a hypothesis for a stretching spring investigation might be: ‘If the force applied to the spring is doubled, then the extension will also double, because the spring obeys Hooke’s law within its elastic limit.’ This prediction can then be tested by collecting data.
例如，对于弹簧拉伸探究的假设可以是：“如果施加在弹簧上的力加倍，那么伸长量也将加倍，因为在弹性限度内弹簧遵循胡克定律。”然后就可以通过收集数据来检验这一预测。
A good hypothesis is specific and quantitative whenever possible. It also makes it easier to decide what range of values to use for the independent variable and how to record the results.
一个好的假设应尽可能具体和定量。它还能帮助我们更容易地确定自变量的取值范围以及记录结果的方式。
4. Designing a Fair Test | 设计公平实验
A fair test is one in which only the independent variable is allowed to affect the dependent variable. All other conditions must be kept strictly the same. This involves careful planning, from selecting apparatus to writing a step-by-step procedure.
公平测试指的是只允许自变量影响因变量，而所有其他条件都必须严格保持一致。这就需要进行细致的规划，从选择仪器到编写分步步骤。
Students must consider how to maintain control variables. For example, in an experiment on the cooling rate of a liquid, the initial temperature, volume of liquid, and type of container must all remain the same across trials. The workbook often prompts learners to list their control measures explicitly.
学生必须考虑如何维持控制变量。例如，在液体冷却速率的实验中，初始温度、液体体积和容器类型在所有试验中都必须相同。练习册经常提示学习者明确列出他们的控制措施。
Additionally, the procedure should include repeats. Taking multiple readings at each value of the independent variable improves reliability and allows an average to be calculated, reducing the impact of random errors.
此外，实验步骤还应包含重复测量。在自变量的每一个取值处记录多个读数可以提高可靠性，并允许计算平均值，从而减小随机误差的影响。
5. Choosing Appropriate Apparatus | 选择合适的仪器
The precision of an experiment depends heavily on the instruments used. For length measurements, a ruler may be suitable for objects of a few centimetres, but a vernier caliper or micrometer is needed for greater precision, such as measuring the diameter of a wire.
实验的精确度在很大程度上取决于所使用的仪器。对于几厘米的物体，用直尺测量可能就足够了，但若要测量导线的直径，则需要使用游标卡尺或千分尺来获得更高的精度。
When choosing a measuring cylinder for volume, a smaller, narrower cylinder generally gives a more accurate reading than a large, wide one for a given volume range. The workbook guides students to select apparatus that matches the required resolution, such as using a digital stopwatch that reads to 0.01 s instead of a wall clock.
选择量筒测量体积时，对于给定的体积范围，较细小的量筒通常能比粗大的量筒提供更准确的读数。练习册指导学生根据所需的分辨率选择仪器，例如使用分辨率为 0.01 秒的数字秒表，而不是墙上的挂钟。
Electrical experiments require careful selection of ammeters and voltmeters with appropriate ranges. Using a 0–1 A ammeter to measure a current of 0.05 A will give a more precise reading than using a 0–10 A ammeter. Understanding instrument sensitivity is a key skill developed through the workbook tasks.
电学实验需要根据量程精心选择电流表和电压表。用一个 0–1 A 的电流表去测量 0.05 A 的电流，会比用 0–10 A 的电流表得到更精确的读数。理解仪器的灵敏度是练习册任务中培养的一项关键技能。
6. Making Measurements and Recording Data | 进行测量和记录数据
Accurate measurement is fundamental. Students must learn to read scales correctly, avoiding parallax error by positioning the eye directly in front of the pointer or the meniscus of a liquid.
精确测量是基础。学生必须学会正确读取刻度，通过将眼睛正对指针或液面凹面来避免视差误差。
All data should be recorded immediately in a well-organised table, with clear headings and units. For example, in a table for a spring extension experiment, the first column might be ‘Force (N)’ and the second ‘Extension (cm)’. The workbook consistently encourages the use of ruled tables with the correct units in brackets.
所有数据都应立即记录在一个条理清晰的表格中，表头要清楚标明单位和量。例如，在弹簧拉伸实验的表格中，第一列可能是“力 (N)”，第二列是“伸长量 (cm)”。练习册一贯鼓励使用带边框的表格，并在括号中注明正确单位。
It is also important to record raw data rather than performing calculations mentally. For instance, if measuring the period of a pendulum, record the time for 10 complete swings, then divide by 10. Never record the calculated period as if it were a direct reading.
记录原始数据而非心算结果也很重要。例如，在测量单摆周期时，应记录 10 次完整摆动的时间，然后除以 10。切勿将计算出的周期当作直接读数来记录。
7. Presenting Data: Tables and Graphs | 数据展示：表格与图表
Once data are collected, they must be presented in a way that reveals patterns. Tables should have independent variables in the left column and dependent variables in the right. Here is a typical data table for a simple pendulum investigation:
收集完数据后，必须以能够揭示规律的方式呈现。表格应将自变量放在左列，因变量放在右列。以下是一个单摆探究的典型数据表示例：
| Length, L (cm) | Time for 10 swings, t₁ (s) | Time for 10 swings, t₂ (s) | Mean time (s) | Period, T (s) |
|---|---|---|---|---|
| 20.0 | 9.05 | 8.95 | 9.00 | 0.900 |
| 40.0 | 12.80 | 12.75 | 12.78 | 1.278 |
Graphs transform tables into visual form. Usually, the independent variable is plotted on the x-axis and the dependent variable on the y-axis. A line graph is suitable for continuous data, while a bar chart is used for categories. The workbook tasks often ask students to plot points, draw a line of best fit, and identify anomalous points.
图表将表格转化为可视形式。通常，自变量标在 x 轴上，因变量标在 y 轴上。折线图适用于连续数据，条形图则用于分类数据。练习册中的任务经常要求学生描点、绘制最佳拟合线并识别异常点。
The line of best fit does not have to pass through all points, but should have a roughly equal number of points above and below it. If the graph suggests a straight line passing through the origin, the variables are directly proportional.
最佳拟合线不一定要经过所有点，但应该使得上下分布的点数量大致相等。如果图形显示一条通过原点的直线，则两个变量成正比关系。
8. Analyzing Results and Drawing Conclusions | 分析结果并得出结论
After plotting the graph, students need to interpret the shape. A straight line through the origin indicates direct proportionality, while a curve might suggest an inverse relationship or a square-law dependence. The workbook guides learners to use mathematical language such as ‘as X doubles, Y also doubles’ to describe patterns.
绘制图表后，学生需要解读图形。一条通过原点的直线表示正比关系，而曲线则可能提示反比关系或平方律依赖关系。练习册引导学生使用数学语言（如“当 X 加倍时，Y 也加倍”）来描述规律。
Conclusions must refer back to the hypothesis. For instance, if the investigation tested ‘Does the angle of a ramp affect the speed of a trolley?’, the conclusion should state whether the data support the idea that larger angles produce higher speeds, and include a brief justification using the trend.
结论必须回扣假设。例如，如果探究的问题是“斜面角度是否影响小车的速度？”，结论就应说明数据是否支持“角度越大速度越高”的设想，并扼要地引用趋势来说明理由。
Where possible, students should express the relationship as an equation. In the stretching spring example, it may be written as F = kx, where k is the spring constant. If the spring is stretched beyond its elastic limit, the relationship breaks down, and the student should note that Hooke’s law no longer applies.
在可能的情况下，学生应将关系表达为方程。在弹簧拉伸的示例中，可以写作 F = kx，其中 k 是弹簧常数。如果弹簧被拉伸超过了弹性限度，这种关系就不成立了，学生应指出胡克定律不再适用。
9. Evaluating the Experiment: Sources of Error and Improvements | 实验评估：误差来源与改进
No experiment is perfect. Evaluation involves identifying sources of error and suggesting realistic improvements. Random errors, such as human reaction time when using a stopwatch, can be reduced through repeats and averaging. Systematic errors, such as a zero error on a Newton meter, must be corrected by adjusting the instrument or subtracting the zero reading.
没有实验是完美的。评估包括找出误差来源并提出切实可行的改进方法。随机误差（如使用秒表时的人为反应时间）可以通过重复测量和求平均值来减小。系统误差（如弹簧测力计的零位误差）则必须通过调整仪器或减去零位读数来修正。
In electrical experiments, heating of components can cause resistance to change, introducing an uncontrolled variable. An improvement might be to switch off the circuit between readings. The workbook encourages students to look critically at their own methods and suggest at least two sensible improvements.
在电学实验中，元件的发热会导致电阻变化，从而引入一个未控制的变量。改进方法可以是在读数间隔期间断开电路。练习册鼓励学生批判性地审视自己的方法，并至少提出两条合理的改进建议。
Another aspect of evaluation is considering whether the range of the independent variable was sufficient and whether the intervals were chosen wisely. For example, taking readings every 10 g may miss subtle changes; 5 g intervals would give a more detailed picture.
评估的另一方面是考虑自变量的取值范围是否足够，以及间隔选取是否恰当。例如，每 10 克取一次读数可能会漏掉细微的变化，而 5 克的间隔则能提供更详细的图像。
10. Safety in the Laboratory | 实验室安全
Safety must always be the first consideration. Before beginning any investigation, students should identify potential hazards and list precautions. Common hazards in physics practical work include heavy masses falling, sharp edges on wires, hot lamps, and possible electric shocks.
安全必须始终是首要考虑的问题。在开始任何探究之前，学生都应识别潜在危险并列出预防措施。物理实验中的常见危险包括重物坠落、导线锐边、高温灯泡以及可能发生的电击。
When stretching a spring, a safety screen might be needed in case the spring snaps. When using a ray box, care must be taken not to look directly into bright light. Eyeglasses should be worn whenever there is a risk of projectiles. The workbook includes safety notes and often asks students to write their own safety rules for a given experiment.
在拉伸弹簧时，可能需要防溅屏以防弹簧突然断裂。使用光线盒时，必须避免直视强光。只要存在飞溅风险，就应佩戴护目镜。练习册不仅包含了安全提示，还经常要求学生为某一实验编写自己的安全规则。
11. Example Investigation: Stretching a Spring (Hooke’s Law) | 实验案例：弹簧的拉伸（胡克定律）
This classic investigation appears prominently in the workbook and illustrates nearly all experimental skills. The aim is to find how the extension of a spring depends on the applied force.
这个经典探究在练习册中占据重要位置，几乎展现了所有实验技能。目的是找出弹簧的伸长量如何取决于所施加的力。
The independent variable is the force (or load), applied by hanging slotted masses. The dependent variable is the extension, found by subtracting the original length from the stretched length. Control variables include the spring itself, the point of suspension, and the way extension is measured (always reading the bottom of the mass hanger).
自变量是力（或载荷），通过悬挂槽码来施加。因变量是伸长量，由拉伸后的长度减去原长得到。控制变量包括弹簧本身、悬挂点以及测量伸长的方式（始终读取砝码钩的底部）。
Data are recorded in a table like this:
数据记录在一个类似下表中：
| Load (N) | Length of spring (cm) | Extension (cm) |
|---|---|---|
| 0.0 | 5.0 | 0.0 |
| 1.0 | 9.1 | 4.1 |
When a graph of extension against force is plotted, the initial linear portion gives the spring constant k. The conclusion should state that extension is directly proportional to force up to the elastic limit, in agreement with Hooke’s law. Beyond this point, the spring deforms permanently and the graph curves.
绘制伸长量随力变化的图像时，最初的直线部分给出了弹簧常数 k。结论应说明在弹性限度内伸长量与力成正比，这与胡克定律相符。超过该点后，弹簧发生永久变形，图像发生弯曲。
In evaluation, students might point out that the ruler used to measure length could have a zero error, and that if the spring coils are tight, the initial extension may be underestimated. Improvements include using a pointer on the spring and a fixed scale to reduce parallax.
在评估中，学生可能指出测量长度所用的尺子可能存在零误差，而且如果弹簧的线圈很紧，初始伸长量可能被低估。改进方法包括在弹簧上加装指针并使用固定标尺，以减小视差。
12. Example Investigation: Current and Voltage in a Circuit | 实验案例：电路中的电流与电压
Another core investigation in the Cambridge Secondary workbook explores the relationship between the current flowing through a resistor and the voltage across it. This forms the basis for understanding Ohm’s law.
剑桥初中练习册中的另一个核心探究是探索流过电阻的电流与其两端电压之间的关系，这是理解欧姆定律的基础。
Using a simple circuit with a variable power supply, a fixed resistor, an ammeter and a voltmeter, students vary the voltage and measure the current. The independent variable is voltage, the dependent variable is current, and control variables include the resistor itself and the temperature (the circuit should be switched off between readings to prevent heating).
使用一个由可变电源、固定电阻、电流表和电压表组成的简单电路，学生改变电压并测量电流。电压是自变量，电流是因变量，控制变量包括电阻本身和温度（实验中应在记录读数之间断开电路，以防止发热）。
When plotted, the graph of current against voltage is a straight line through the origin for an ohmic conductor, confirming that current ∝ voltage, and hence V = IR. The gradient of the line gives 1/R.
在欧姆导体中，电流随电压变化的图像是一条通过原点的直线，这证实了电流与电压成正比，因此 V = IR。直线的斜率给出 1/R 的值。
Common errors in this investigation include connecting the ammeter in parallel (it must be in series) and the voltmeter in series (it must be in parallel). Students should be able to explain how their results would be affected by these mistakes. The workbook questions often address such circuit errors explicitly.
这个探究中常见的错误包括将电流表并联（它必须串联）和将电压表串联（它必须并联）。学生应能解释这些错误会如何影响结果。练习册中的问题经常明确涉及此类电路错误。
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