📚 PH01 Experimental Investigation International Physics AS 9 May 2023 | 国际物理AS实验探究（2023年5月9日PH01）
Welcome to this focused revision guide on tackling the experimental investigation component of the Edexcel International AS Physics PH01 paper, which took place on 9 May 2023. In this article, we will break down every stage of a typical AS-level practical enquiry – from clarifying the aim and planning the procedure to collecting data, analysing graphs, and evaluating uncertainties. Mastering these steps is essential for performing well in the written alternative-to-practical exam, where you will be asked to design experiments, process results, and assess sources of error without actually entering a laboratory.
欢迎阅读这篇针对Edexcel国际AS物理PH01实验探究部分的重点复习指南，该考试于2023年5月9日进行。本文将逐步拆解典型的AS阶段实验探究——从明确目标和制定计划，到数据采集、图像分析和不确定度评估。掌握这些步骤对于在纸笔实验考试中取得好成绩至关重要，因为考试要求你无需进入实验室就能够设计实验、处理数据并评估误差来源。
1. Clarifying the Experimental Aim | 明确实验目标
Before you write a single word about apparatus or procedure, you must identify the dependent and independent variables precisely. In many PH01 investigations, the aim is to determine a physical constant, such as the acceleration of free fall g, the resistivity ρ of a metal wire, or the internal resistance r of a cell. Read the question stem carefully and underline the quantity to be found. Then express the aim in the form: “Investigate the relationship between X and Y, hence determine Z”. This clarity will guide your entire answer.
在你动笔写下任何仪器或步骤之前，必须明确区分因变量和自变量。在PH01的许多探究题中，目标通常是测定某个物理常数，比如自由落体加速度g、金属丝的电阻率ρ或是电池的内阻r。仔细阅读题干，把需要求出的量划出来，然后把目标表述为：“探究X与Y之间的关系，从而测定Z”。这样的清晰度将引导你完成整道题的作答。
2. Identifying Independent, Dependent, and Control Variables | 识别自变量、因变量和控制变量
The independent variable is the quantity you deliberately change (e.g., length of a wire L, current I through a component, or height h from which a ball is dropped). The dependent variable is the quantity that responds to the change (e.g., potential difference V, time of fall t, or balance reading). Control variables are those that must be kept constant to ensure a fair test. For a resistivity experiment, for instance, the diameter of the wire and its temperature are critical controls. List all three categories explicitly in the exam.
自变量是你有意识改变的量（如导线长度L、通过元件的电流I或小球下落的高度h）。因变量是随自变量变化而响应的量（如电势差V、下落时间t或天平读数）。控制变量是那些必须保持不变以确保实验公平的量。例如，在电阻率实验中，导线直径与温度就是关键的控制变量。在考试中要清晰列出这三类变量。
3. Choosing and Justifying Apparatus | 仪器的选择与理由
Always select instruments that offer adequate resolution and sensitivity for the measurements required. If you are measuring a diameter of about 0.5 mm, a micrometer screw gauge (resolution 0.01 mm) is far more appropriate than a vernier caliper (typically 0.1 mm). To measure a time interval of 0.5 s, a digital stopwatch reading to 0.01 s is acceptable, but an electronic timer using light gates will reduce reaction-time errors. For circuit experiments, a digital ammeter with 0.01 A resolution might be needed. In your answer, state the instrument and briefly justify your choice by linking resolution to the magnitude being measured.
始终选择对所测量量具有足够分辨率和灵敏度的仪器。如果要测量约0.5 mm的直径，千分尺（分辨率0.01 mm）远比游标卡尺（通常0.1 mm）更适合。要测量0.5 s的时间间隔，读数精确到0.01 s的数字秒表是可以接受的，但使用光门的电子计时器将减少反应时间误差。对于电路实验，可能需要分辨率为0.01 A的数字电流表。在答题时，说出仪器名称，并简要说明理由，将分辨率与被测量的大小联系起来。
4. Describing a Clear and Repeatable Procedure | 写出清晰且可重复的操作步骤
Good experimental writing uses the third person passive voice and avoids ambiguity. For example, “A copper wire of length 1.000 m was clamped. The current was adjusted to 0.50 A and the potential difference across the wire was recorded.” Include steps for varying the independent variable systematically and for recording repeated readings. Mention any safety precautions, such as switching off the power supply between readings to avoid heating the wire, or wearing eye protection when using a high-voltage source.
好的实验写作采用第三人称被动语态，避免含糊。例如，“夹紧一根长度为1.000 m的铜导线。调节电流至0.50 A，记录导线两端的电势差。”要包含系统改变自变量以及记录重复读数的步骤。提及所有安全注意事项，比如两次读数之间关断电源以防止导线发热，或在使用高压电源时佩戴护目镜。
5. Designing Data Tables and Recording Results | 设计数据表与记录结果
A well-structured results table has physical quantities in the headings along with their SI units separated by a slash, e.g., Length, L / m. The table should allow for multiple readings (at least three) and a column for the mean value. Consistent decimal places and significant figures must be used. For example, if a voltmeter reads to 0.01 V, every entry in the V column should appear as 1.58 V, not 1.6 V. In the exam, you may be given raw data and asked to identify anomalous readings or calculate mean values, so always scan for outliers.
结构良好的结果表格会在表头中列出物理量及其国际单位，用斜线分隔，例如 Length, L / m。表格应留出多次读数（至少三次）的位置，并设平均值一列。小数点位数和有效数字必须保持一致。例如，如果电压表读到0.01 V，那么V列中的每个数据都该写作1.58 V，而非1.6 V。考试中可能会给你原始数据，让你找出异常值或计算平均值，因此始终要留意离群数据。
6. Plotting a Graph and Drawing the Line of Best Fit | 绘制图像并画出最佳拟合线
Use the largest available grid area. Label axes with the quantity and unit, e.g., (V / V), and choose scales that are linear, easy to interpret (multiples of 1, 2, or 5), and avoid awkward subdivisions. Plot points with small, sharp crosses or dots encased in a circle. The line of best fit should have a balanced distribution of points on either side – it need not pass through the origin unless the theory demands it. For a non-linear trend, draw a smooth curve. The PH01 paper often asks you to explain why a certain point does not lie on the line; this is your cue to discuss an experimental error affecting that particular measurement.
要尽可能利用图纸面积。用物理量及其单位标注坐标轴，例如 (V / V)，并选择线性的、易于读取的比例（1、2、5的倍数），避免别扭的分格。用小而清晰的十字叉或带圆点标记数据点。最佳拟合线应在两侧均匀分布数据点——除非理论要求，否则直线不一定经过原点。对于非线性趋势，画一条平滑曲线。PH01试卷常会问为什么某点不在线上，这时候就要讨论影响该次测量的实验误差。
7. Calculating the Gradient and Intercept | 计算斜率和截距
Use a large triangle on the best-fit line, taking coordinates directly from the graph. The gradient m is given by Δy/Δx. Avoid using data points that were used to plot the graph; instead, select two widely separated points on the line itself. Then, link the gradient (or intercept) to the physical constant being determined. For example, in a free-fall experiment, plotting distance fallen s against t²/2 yields a gradient equal to g. Clearly show your working and state your final value with an appropriate unit.
在最佳拟合线上取一个大三角形，直接从图上读取坐标。斜率m由Δy/Δx给出。避免使用原始数据点，而应选择线上两个相距较远的点。然后将斜率（或截距）与待测物理常量联系起来。例如，在自由落体实验中，用下落距离s对t²/2作图，得到的斜率就等于g。务必展示计算过程，并写出带单位的最终数值。
8. Assessing Uncertainties and Drawing Error Bars | 评估不确定度并绘制误差棒
Uncertainty in a single measurement is typically taken as ± half the smallest scale division. For quantity calculated from multiple measurements, the absolute uncertainty is estimated from the range: (max − min) / 2. When plotting error bars, extend them vertically and horizontally to represent absolute uncertainties in the dependent and independent variable, respectively. The PH01 exam may ask you to draw a worst-fit line (steepest or shallowest) through the error bars, then determine the uncertainty in the gradient: Δm = |mmax − mmin| / 2. State the final result as m ± Δm, quoting the same number of decimal places in both.
单次测量的不确定度通常取最小分度值的一半。对于由多次测量计算得到的量，绝对不确定度由极差估计：(最大值 − 最小值) / 2。绘制误差棒时，分别用竖直和水平误差棒表示因变量和自变量的绝对不确定度。PH01考试可能要求你通过误差棒画出一条最坏拟合线（最陡或最浅），然后确定斜率的不确定度：Δm = |mmax − mmin| / 2。最终结果表述为m ± Δm，两者小数位数保持一致。
9. Evaluating the Experiment and Identifying Limitations | 评估实验并指出局限性
No experiment is perfect. You are expected to discuss both random and systematic errors. A random error (e.g., timing inconsistency due to human reaction) can be reduced by repeating readings and using averages, or by introducing light gates and data-logging. Systematic errors (e.g., zero error on a micrometer, parallax when reading a voltmeter) can be reduced by calibrating instruments and reading scales at eye level. In your evaluation, rank the largest sources of uncertainty and explain how they affect the final result. This section is frequently awarded high marks in the alternative-to-practical paper.
没有哪个实验是完美的。你需要同时讨论随机误差和系统误差。随机误差（如因人体反应导致的计时不一致）可通过重复读数取平均值，或使用光门和数据记录设备来减小。系统误差（如千分尺的零位误差、读电压表时的视差）可通过校准仪器和眼平读数来减小。在评估环节中，要按大小排序误差来源，并说明它们如何影响最终结果。这部分在替代实验考试中往往分值很高。
10. Comparing Results with Accepted Values | 将结果与公认值进行比较
Calculate the percentage difference between your experimental value and a standard reference value using (|E − A| / A) × 100%. To judge if your result is accurate, compare this percentage difference with your experimental percentage uncertainty. If the difference is smaller than the uncertainty, the result is consistent with the accepted value within experimental error. If larger, systematic errors are likely present. The PH01 exam sometimes provides a standard value and asks you to comment on the reliability of your experiment. Frame your answer around this comparison.
计算实验值与标准参考值之间的百分差：(|E − A| / A) × 100%。要判断结果的准确性，可将这个百分差与实验百分不确定度进行对比。如果差值小于不确定度，说明结果在实验误差范围内与公认值一致。若差值更大，则可能存在系统误差。PH01考试有时会给出标准值，要求你评价实验的可靠性。你的答案应围绕这一比较展开。
11. Typical PH01 Experiment: Determining the Resistivity of a Wire | 典型的PH01实验：测定导线的电阻率
Let us apply these ideas to a common AS investigation. To find the resistivity ρ of a metal, you would measure the resistance R of a wire of known length L and diameter d. The resistance is obtained by recording the potential difference V across the wire and the current I through it for several values of L, keeping I constant to minimize heating. A graph of R (y-axis) against L (x-axis) yields a straight line through the origin, with gradient = ρ / A, where cross‑sectional area A = πd² / 4. Then ρ = gradient × (πd² / 4). Uncertainties in d and the gradient both contribute to the uncertainty in ρ, so careful micrometer measurements and multiple readings of d at different positions are crucial.
让我们把这些要点应用到一项常见的AS探究中。要测定金属的电阻率ρ，需测量长度为L、直径为d的导线的电阻R。电阻的获取方法是：保持电流I恒定以尽量减少发热，记录导线两端的电势差V和流过导线的电流I，并在多个L值下重复。以R（纵轴）对L（横轴）作图，得到一条通过原点的直线，斜率 = ρ / A，其中横截面积A = πd² / 4。于是 ρ = 斜率 × (πd² / 4)。直径d和斜率的不确定度都会影响ρ的不确定度，因此仔细使用千分尺并在不同位置多次测量d至关重要。
12. Exam Technique and Final Checks | 考试技巧与最后检查
On the 9 May 2023 PH01 paper, time management is critical. Allocate about 30–35 minutes to the experimental question. Read the entire question first, then plan your answers logically. When asked to suggest improvements, be specific: instead of “use better equipment”, write “use a laser distance sensor to eliminate parallax error in measuring extension”. Always include units, and check that calculated values have a realistic size. Finally, remember that explaining your reasoning is often worth more marks than obtaining a numerically perfect answer.
在2023年5月9日的PH01考试中，时间管理至关重要。给实验题分配约30–35分钟。先通读整道题目，再有逻辑地规划答案。当被要求提出改进建议时，要具体：不说“使用更好的设备”，而写“使用激光距离传感器消除测量伸长量时的视差”。务必带上单位，并检查计算结果是否具有合理的大小。最后，请记住，解释推理过程往往比算出一个数值完美的答案分值更高。
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