📚 AS Physics Unit 3: Experimental Investigation Mark Scheme Insights (June 2019) | AS 物理 Unit 3 实验探究评分方案解读（2019年6月）
Understanding the mark scheme is one of the fastest ways to improve your performance in the AS Physics Unit 3 experimental investigation paper. The June 2019 series provides a clear blueprint of what examiners expect in terms of experimental design, data handling, graphical analysis, and evaluation. This article distils the key insights from that mark scheme, turning examiner thinking into a practical revision tool. By working through the assessment objectives, you will learn how to avoid common pitfalls and structure answers that consistently score top marks.
理解评分方案是提高 AS 物理 Unit 3 实验探究表现的最快途径之一。2019 年 6 月考卷明确展示了考官对实验设计、数据处理、图形分析和评价方面的期望。本文将提炼此评分方案的关键信息，将考官的思考方式转化为实用的复习工具。通过逐一梳理评估目标，你将学会如何避开常见错误，并构建出能持续获得高分的答案结构。
1. Overview of Unit 3 Experimental Investigation | 单元3实验探究概述
Unit 3 of AS Physics focuses entirely on practical skills. You are assessed on your ability to plan experiments, record and process data, draw graphs, analyse results, and evaluate the method. The June 2019 question paper typically presents a scenario where you must determine a physical quantity, such as the resistivity of a wire or the spring constant of a spring, using a given set of apparatus.
AS 物理第三单元完全聚焦于实践技能。考察内容包括实验计划、数据记录与处理、作图、结果分析以及方法评价。2019 年 6 月的试题通常给出一个具体情景，要求你利用给定的器材测定一个物理量，例如导线的电阻率或弹簧的劲度系数。
The mark scheme is designed to reward precise scientific language, correct use of significant figures, and a logical approach to uncertainty. Even if your numerical answer is slightly off, you can gain substantial credit for demonstrating sound method and thorough evaluation.
评分方案的设计旨在奖励精准的科学用语、正确运用有效数字以及处理不确定度的逻辑思路。即使数值答案略有偏差，只要展示出合理的方法和全面的评价，你仍然可以获得大部分分数。
2. Understanding the Mark Scheme Structure | 理解评分方案结构
The June 2019 mark scheme divides marks across several sections: planning (P), implementation and measurements (I), analysis (A), and evaluation (E). Each section contains statements that describe what a candidate must do to earn the mark. Some marks are awarded for a single correct word, while others are for a sequence of calculations.
2019 年 6 月的评分方案将分数划分为几个部分：计划 (P)、实施与测量 (I)、分析 (A) 和评价 (E)。每个部分都包含具体描述，说明考生必须完成什么才能得分。有些分数仅凭一个正确词汇即可获得，而有些则需要一连串的计算。
Examiners use a point‑based system: if your answer matches the marking point, you get the mark. There is usually no penalty for errors that are carried forward as long as your working is clear. Understanding which ideas are ‘reject’ and which are ‘allow’ helps you target the most secure marks first.
考官采用采分点体系：如果你的答案与采分点相符，便能得到该分数。只要解题步骤清晰，一般不会因为前一步的错误而扣掉后续的分数。理解哪些表述会被“拒绝”、哪些会被“允许”，有助于你优先锁定最稳妥的分数。
3. Key Assessment Objectives | 关键评估目标
Three assessment objectives dominate the June 2019 paper: AO2 (application of knowledge), AO3 (analyse, interpret and evaluate), and AO1 (recall of practical techniques). AO2 is tested through questions that ask you to explain why a particular piece of equipment is suitable or to describe how to control a variable. AO3 appears in the graph work and the evaluation of results.
2019 年 6 月试卷主要考查三个评估目标：AO2（应用知识）、AO3（分析、解释与评价）以及 AO1（对实验技术的记忆）。AO2 通过要求解释为何某种器材合适或如何控制变量来测试；AO3 则体现在图形处理和结果评价中。
The mark scheme reveals that AO1 marks often come from correct naming of apparatus and stating standard procedures, like checking for a zero error. To maximise your score, you must be able to identify the underlying physics in the investigation and then express it clearly.
评分方案显示，AO1 的分数往往来自正确命名器材和陈述标准步骤，例如检查零点误差。为了最大化得分，你必须能识别实验背后蕴含的物理原理，并清晰地表达出来。
4. Planning an Experiment: Variables and Controls | 规划实验：变量与控制
The planning section of the June 2019 mark scheme rewards candidates who can identify the independent, dependent, and control variables without ambiguity. For example, in a wire‑stretching experiment, the independent variable is the force applied (or mass added), the dependent variable is the extension, and control variables include the original length and cross‑sectional area.
2019 年 6 月评分方案中的计划部分奖励那些能够明确区分自变量、因变量和控制变量的考生。例如，在拉伸金属丝的实验中，自变量是施加的力（或增加的质量），因变量是伸长量，控制变量则包括原长和横截面积。
You should always justify how you will keep a control variable constant. The mark scheme accepts 'use the same wire' and 'measure diameter in several places with a micrometer, then find the mean'. Repeating measurements is considered a control technique itself, as it reduces the effect of random errors.
你应该始终说明如何使控制变量保持恒定。评分方案接受“使用同一根金属丝”以及“用千分尺在多处测量直径，然后取平均值”这样的表述。重复测量本身也被视作一种控制手段，因为它能减小随机误差的影响。
5. Data Collection and Table Design | 数据采集与表格设计
For full marks in data collection, the June 2019 mark scheme expects a table with correct headings and units. The independent variable must be recorded in the first column, followed by the dependent variable. Units should appear in the heading, often written as 'length / m' or 'potential difference / V'.
要在数据采集中获得满分，2019 年 6 月的评分方案要求表格必须有正确的标题和单位。自变量应记录在第一列，随后是因变量。单位应写在标题中，例如“长度 / m”或“电势差 / V”。
All raw data must be given to an appropriate number of significant figures, matching the precision of the instrument. The mark scheme requires at least six sets of readings, and you must take repeat readings for at least one pair and calculate a mean. A column for 'average' or 'mean' with consistent precision is expected.
所有原始数据的有效数字位数必须恰当，与仪器精度相匹配。评分方案要求至少六组读数，并且必须至少对其中一组进行重复测量并计算平均值。表格中应包含“平均值”列，且精度一致。
6. Graphical Analysis and Line of Best Fit | 图形分析与最佳拟合线
The June 2019 mark scheme insists on a graph with labelled axes, proper scales, and accurately plotted points. The axes must use the standard format 'quantity / unit'. The line of best fit should be a single straight line (or smooth curve, if appropriate) that passes through as many points as possible, with an equal number of points above and below the line.
2019 年 6 月的评分方案强调，图表必须带有轴标签、合适的刻度以及精确描出的数据点。坐标轴须采用标准格式“物理量 / 单位”。最佳拟合线应为一条直线（或视情况而定的光滑曲线），尽可能多地穿过数据点，并且线上方和下方的点数量大致相等。
Candidates often lose marks by using a broken scale or by forcing the line through the origin when there is no physical reason to do so. The mark scheme indicates that the line of best fit does not have to pass through the origin unless the investigation demands it.
考生常因使用断裂刻度或在不具备物理原因的情况下强行使直线通过原点而失分。评分方案指出，除非实验本身要求如此，否则最佳拟合线不必经过原点。
7. Calculating Gradient and Intercept | 计算斜率和截距
Marks for gradient calculation in the June 2019 analysis section require you to use a large triangle on the best‑fit line. The mark scheme awards marks for reading coordinates correctly from the line, showing the changes in both x and y, and then computing the gradient as gradient = Δy / Δx.
2019 年 6 月分析部分中有关斜率计算的分数，要求你在最佳拟合线上使用一个大三角形。评分方案对从线上正确读取坐标、展示 x 和 y 的变化量、然后按 gradient = Δy / Δx 计算斜率的步骤单独给分。
The intercept should be determined by extending the line to the y‑axis, or by using the equation of a straight line. For an experiment to determine the Young modulus, the mark scheme expects you to link the gradient to a physical quantity, such as gradient = E / A, where A is the cross‑sectional area.
截距应通过将直线延伸至 y 轴或利用直线方程求得。对于测定杨氏模量的实验，评分方案要求你将斜率与物理量联系起来，例如 gradient = E / A，其中 A 为横截面积。
If a candidate calculates the gradient from raw data points rather than from the line of best fit, the mark is not awarded. This is a classic pitfall highlighted in the June 2019 examiner report.
如果考生从原始数据点而非最佳拟合线计算斜率，该分数则无法获得。这是 2019 年 6 月考务报告中强调的一个典型失分点。
8. Uncertainty and Error Analysis | 不确定度与误差分析
Uncertainty calculations are a recurring feature. The mark scheme accepts the half‑range method for a set of repeats: uncertainty = (max − min) / 2. If only one measurement is taken, the uncertainty is usually the instrument's precision, but you should state this assumption.
不确定度计算是一个常考内容。评分方案接受对一组重复数据使用半程法：不确定度 = (最大值 − 最小值) / 2。如果只进行了一次测量，不确定度通常取仪器的精度，但你需要明确说明这一假定。
For percentage uncertainty in a derived quantity, the June 2019 mark scheme expects you to combine individual percentage uncertainties. In simple cases, when quantities are multiplied or divided, you add the percentage uncertainties. A correct calculation looks like: %U(Y) = %U(m) + %U(g) + %U(x).
对于导出量的百分不确定度，2019 年 6 月的评分方案要求对各部分的百分不确定度进行合成。在简单情况下，当物理量相乘或相除时，应相加各自的百分不确定度。正确的计算形如：%U(Y) = %U(m) + %U(g) + %U(x)。
The number of significant figures in the uncertainty should match the reading precision. The mark scheme penalises answers that give an uncertainty to 3 significant figures when the measuring instrument only reads to 2 significant figures.
不确定度的有效数字位数应与读数精度相匹配。评分方案会对测量仪器仅读到两位有效数字、而不确定度却给出三位有效数字的答案进行扣分。
9. Percentage Difference and Validity | 百分比差异与有效性
After determining an experimental value, you are often asked to compare it with a known or standard value using the percentage difference: % difference = |experimental − accepted| / accepted × 100%. The June 2019 mark scheme uses this to judge whether the result is accurate or within experimental uncertainty.
在得出实验值后，经常要求你通过百分比差异将其与已知值或标准值进行比较：% difference = |实验值 − 公认值| / 公认值 × 100%。2019 年 6 月的评分方案利用该计算来判断结果是否准确，或者是否在实验误差范围内。
A percentage difference smaller than the experimental uncertainty suggests the result is reliable and supports the underlying theory. If the percentage difference is large, the candidate must recognise the discrepancy and refer to systematic errors in the evaluation. The mark scheme gives credit for a clear statement linking percentage difference to validity.
若百分比差异小于实验不确定度，则表明结果可靠，支持背后的理论。若百分比差异较大，考生必须认识到这种不一致，并在评价中提及系统误差。评分方案会对明确将百分比差异与有效性联系起来的陈述给予分数。
10. Evaluation and Improvements | 评价与改进措施
The evaluation section often carries heavy weighting. The June 2019 mark scheme shows that you must identify at least two sources of uncertainty or error, explain their effect on the final result, and suggest practical improvements. Generic statements like 'use more precise equipment' without detail do not gain marks.
评价部分通常占分较重。2019 年 6 月的评分方案表明，你必须至少指出两个不确定度或误差来源，解释它们对最终结果的影响，并提出具体的改进措施。类似“使用更精密的设备”这样缺乏细节的笼统表述不会得分。
Effective evaluation points from the mark scheme include: 'attaching a fiducial marker to reduce parallax when reading the ruler', 'using a set square to ensure the ruler is vertical', or 'taking readings of the diameter in two perpendicular directions to account for non‑uniformity'. These are specific and link to the physics.
评分方案中有效的评价点包括：“粘贴一个基准标记以减少读数时的视差”、“用三角尺确保直尺垂直”或“在两个正交方向上测量直径以考虑不均匀性”。这些表述具体且与物理原理相关联。
You are also expected to comment on the repeatability of results. The mark scheme rewards candidates who note when a set of repeats shows a large spread and suggest increasing the number of readings or controlling an environmental factor more tightly.
还需要对结果的重复性进行评论。评分方案奖励那些注意到一组重复数据离散度较大，并提议增加读数次数或更严格地控制环境因素的考生。
11. Common Pitfalls in the June 2019 Paper | 2019年6月试卷常见错误
Examiner feedback on the June 2019 series highlights several recurring mistakes. Many candidates plotted the wrong quantity on the x‑axis, confusing independent and dependent variables. The mark scheme clearly penalises inverted axes, even if the graph is otherwise perfect.
2019 年 6 月系列的考务反馈指出了几个反复出现的错误。许多考生在 x 轴上绘制了错误的物理量，混淆了自变量和因变量。评分方案明确对坐标轴颠倒的情况进行扣分，即使图形其他方面都正确。
Another common error was writing the gradient as simply a number without units. The gradient of a potential difference vs. current graph has units of ohms (Ω), and omitting the unit costs a mark. The mark scheme expects the correct unit to match the physics being investigated.
另一个常见错误是写出斜率仅为数字而没有单位。电势差–电流图的斜率单位为欧姆 (Ω)，缺少单位会失分。评分方案期望正确的单位能与所研究的物理量相符。
In the evaluation, candidates frequently mentioned 'human error' or 'inaccurate measuring' without specifying the mechanism. The mark scheme rejects vague statements. Instead, you should say exactly how the error occurred, such as 'difficulty in stopping the stopwatch at the exact moment the light gate was triggered'.
在评价部分，考生经常提到“人为误差”或“测量不准”，却没有说明具体机制。评分方案拒绝含糊其辞的表述。相反，你应当准确描述误差如何发生，例如“很难在光闸被触发的精确瞬间停住秒表”。
Finally, many students failed to check whether their calculated result was within the uncertainty range of the accepted value. The June 2019 mark scheme rewarded those who used their percentage difference and percentage uncertainty to make a judgement about the experiment's success.
最后，许多学生未能检验自己的计算结果是否落在公认值的不确定度范围内。2019 年 6 月的评分方案奖励那些利用百分比差异和百分不确定度对实验成功与否做出判断的考生。
12. Conclusion and Revision Tips | 结论与复习建议
Reading and internalising the June 2019 mark scheme transforms a good practical script into an excellent one. Always align your answers with the explicit marking points: state variables clearly, include units in table headings and graph axes, draw a proper line of best fit, calculate uncertainties systematically, and evaluate with precision.
阅读并消化 2019 年 6 月的评分方案，能将一份不错的实验答卷转变为一份优秀的答卷。始终让你的答案与明确的采分点对标：清晰陈述变量、在表格标题和坐标轴上注明单位、划出恰当的最佳拟合线、系统地计算不确定度，并进行严谨的评价。
Practise past papers under timed conditions, then use the mark scheme to mark your own work. Pay special attention to the 'reject' statements, as they teach you what language to avoid. Rehearse writing evaluations that link a named error to its effect on the measured quantity and a realistic improvement.
在限时条件下练习往年真题，然后用评分方案批改自己的答卷。特别注意那些“拒绝”表述，因为它们能教会你避免使用何种语言。反复练习撰写能将具名误差与测量量的影响以及现实的改进措施联系起来的评价。
Remember that the mark scheme is your best friend in the final weeks of revision. Every bullet point in it is a clue about what the examiner is looking for. By mastering these insights from the June 2019 series, you are equipping yourself to tackle any AS Unit 3 experimental investigation with confidence.
请记住，评分方案是你在最后几周复习中的最佳伙伴。其中的每一个要点都是考官想要看到什么的线索。通过掌握 2019 年 6 月系列带来的这些深层理解，你将有能力自信地应对任何 AS Unit 3 实验探究考试。
Published by TutorHao | Physics Revision Series | aleveler.com
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