📚 AS Physics Unit 3 June 2019: Experiment Investigation | AS 物理单元三 2019 年 6 月实验探究
This article explores the typical experiment-based questions from the June 2019 AS Physics Unit 3 exam paper, highlighting the essential practical skills, data analysis techniques, and error evaluation strategies required. Whether you are preparing for your own practical assessment or seeking to understand how theory applies to hands-on investigations, this walkthrough covers the core experimental principles tested.
本文探讨了 2019 年 6 月 AS 物理单元三试卷中的典型实验问题，重点介绍所需的实验技能、数据分析方法以及误差评估策略。无论你是在为实践评估做准备，还是想了解理论如何应用于动手探究，本解析都涵盖了所考查的核心实验原理。
1. Overview of the AS Unit 3 Practical Paper | 单元三实验试卷概述
AS Unit 3 in Physics is a written examination that assesses practical and investigative skills through structured questions. It typically accounts for a significant portion of the AS qualification and includes activities such as planning experiments, recording observations, tabulating data, plotting graphs, determining quantities from gradients or intercepts, and evaluating sources of uncertainty.
AS 物理单元三是一场书面考试，通过结构化题目评估实验与探究技能。它通常占 AS 资格的较大比重，内容包括规划实验、记录观察、表格整理数据、绘制图表、通过斜率或截距计算物理量以及评估不确定度来源。
In the June 2019 paper, candidates were required to engage with scenarios involving measurements of density, electrical properties, and mechanical oscillations. These contexts test the same core competencies: precision in measurement, appropriate use of instruments, control of variables, valid graphing, and critical analysis of procedures.
在 2019 年 6 月的试卷中，考生需要处理涉及密度测量、电学特性和机械振动的场景。这些情境考查的是同样的核心能力：测量的精确性、仪器的恰当使用、变量控制、有效的图示以及程序的批判性分析。
2. Experiment 1: Determining the Density of a Metal Object | 实验一：测定金属物体的密度
The first major experiment in the paper focused on finding the density of an irregularly shaped metal sample. The method required measuring the mass using a digital balance and determining the volume by displacement of water in a measuring cylinder.
试卷中的第一个主要实验是测定不规则形状金属样品的密度。该方法需要用电子天平测量质量，并通过量筒中的排水法测定体积。
The mass m was recorded directly, while the volume V was calculated from the difference between the final and initial water levels: V = V₂ – V₁. The density ρ was then found using the relationship ρ = m / V.
质量 m 直接记录，而体积 V 通过最终和初始水位差计算得出：V = V₂ – V₁。然后利用关系式 ρ = m / V 求出密度。
ρ = m / (V₂ – V₁)
It is critical to ensure the object is fully submerged without trapping air bubbles, as this would reduce the apparent volume and give an incorrectly high density. Reading the meniscus at eye level also improves accuracy.
关键是要确保物体完全浸没且不附着气泡，因为气泡会减少表观体积，导致密度值偏高。在平视读数弯月面也能提高准确性。
3. Recording Data and Calculating Uncertainties | 记录数据与计算不确定度
Candidates were expected to present mass and volume readings in a table with appropriate headings and units. Each measurement was repeated, and the mean values used to reduce random errors. The uncertainty in mass was taken as the precision of the balance (±0.01 g), while the uncertainty in volume arose from the analogue scale of the measuring cylinder (±0.5 cm³ or half the smallest division).
考生应当将质量与体积读数放入带有适当标题和单位的表格中。每次测量重复进行，用平均值减小随机误差。质量的不确定度取天平的精密度（±0.01 g），而体积的不确定度来自量筒的模拟刻度（±0.5 cm³ 或最小分度值的一半）。
For a derived quantity like density, the percentage uncertainty can be estimated by adding the fractional uncertainties of mass and volume. If a student recorded m = 45.67 g and V = 6.0 cm³, the percentage uncertainty in m is (0.01/45.67)×100% ≈ 0.02%, and in V is (0.5/6.0)×100% ≈ 8.3%. The total percentage uncertainty in density is approximately 8.3%, dominating the error budget.
对于密度这样的导出量，可以通的质量和体积的分数不确定度相加来估算百分不确定度。如果学生记录 m = 45.67 g 和 V = 6.0 cm³，则 m 的百分不确定度为 (0.01/45.67)×100% ≈ 0.02%，V 的为 (0.5/6.0)×100% ≈ 8.3%。密度的总百分不确定度约为 8.3%，在误差预算中占主导。
This analysis helps justify improvements, such as using a larger object to increase the displaced volume and reduce the relative uncertainty, or employing a more precise measuring instrument like a burette.
这一分析有助于论证改进措施，例如使用更大的物体以增加排开液体的体积并减小相对不确定度，或者使用滴定管等更精密的测量仪器。
4. Graph Work: Linearising Density Data | 图像处理：密度数据的线性化
Graphical skills are central to Unit 3, and an extension question asked how the density experiment could be verified using a series of masses. By keeping the material constant, plotting mass against the subtended volume yields a straight line through the origin. The gradient of the mass–volume graph equals the density.
图像技能是单元三的核心，一道延伸题询问如何用一系列质量验证密度实验。在材料不变的情况下，以质量为纵轴、排开液体的体积为横轴作图，会得到一条过原点的直线。质量-体积图的斜率等于密度。
m = ρ V
A scatter plot with a best-fit line allows students to identify anomalous points and to deduce density without relying on a single pair of readings. The line must be drawn with a sharp pencil to minimise thickness error, and the gradient should be calculated over at least half the length of the line.
带有最佳拟合线的散点图能让学生识别异常点，并推导出密度而不依赖于单对读数。线条必须用削尖的铅笔绘制以减小厚度误差，且应在至少线长一半的范围内计算斜率。
5. Experiment 2: I–V Characteristics of a Filament Lamp | 实验二：白炽灯的 I-V 特性
A common electricity investigation required students to plot the current–voltage graph for a filament lamp and interpret its shape. The circuit typically consists of a variable DC supply, a filament bulb, an ammeter in series, and a voltmeter in parallel. A variable resistor or a potential divider arrangement is used to vary the voltage across the bulb smoothly.
一个常见的电学探究要求学生绘制白炽灯的电流-电压图并解释其形状。电路通常由一个可调直流电源、一个白炽灯泡、一个串联的电流表和一个并联的电压表组成。用可变电阻器或分压器装置来平稳地改变灯泡两端的电压。
As the voltage increases, the filament heats up, causing its resistance to rise. Therefore the I–V graph is not a straight line; it curves towards the voltage axis, showing a decreasing gradient at higher currents. This non‑ohmic behaviour is a key practical observation.
随着电压的增大，灯丝升温，其电阻升高。因此 I-V 图并非直线；它弯向电压轴，在较大电流处斜率减小。这种非欧姆行为是一个关键的实验观察结果。
R = V / I
The exam may ask to calculate resistance at a specific point using the tangent or the ratio V/I. Since the graph is curved, resistance is obtained from the coordinates at that point, not from a constant gradient.
试卷可能要求在特定点使用切线或比值 V/I 计算电阻。由于图形是弯曲的，电阻应从该点的坐标获取，而不是从一个恒定的斜率。
6. Circuit Setup and Safety Considerations | 电路搭建与安全考量
In the June 2019 paper, safety and correct circuit assembly were emphasised. The potential divider configuration is preferred over a series rheostat because it can supply zero voltage across the lamp at the start, preventing an initial surge. Students were reminded to connect the voltmeter across the lamp, not the supply, and to start data logging from a low voltage, gradually increasing it.
在 2019 年 6 月的试卷中，安全性和正确的电路装配受到强调。相比串联变阻器，分压器配置更受青睐，因为它能在开始时提供灯泡零电压，防止初始浪涌。题目提醒考生电压表应跨接在灯泡两端而非电源两端，并应从低电压开始记录数据，逐渐调高。
Furthermore, any exposed conductors should be insulated, and the current rating of the lamp must not be exceeded. In a practical write-up, these steps would earn credit for awareness of experimental risks.
此外，任何裸露的导体都应绝缘，且不得超过灯泡的额定电流。在实验报告中，这些步骤会因关注实验风险而得到分数。
7. Tabulating and Processing Electrical Data | 电气数据的表格化与处理
Data tables for the filament lamp experiment should include columns for voltage V, current I, and optionally calculated resistance R. Consistent significant figures must be maintained: e.g., if a voltmeter reads to 0.01 V, all readings should be recorded to two decimal places.
白炽灯实验的数据表应包含电压 V、电流 I 以及可选的计算电阻 R 的列。有效数字必须保持一致：例如，如果电压表读到 0.01 V，所有读数都应记录到小数点后两位。
Anomalies are identified by comparing the shape of the plotted curve with the expected trend. Any point that lies significantly off the smooth curve should be circled and repeated if time allows. Repeating the whole experiment with a fresh bulb can also test reproducibility.
通过比较绘制曲线的形状与预期趋势来识别异常点。任何明显偏离平滑曲线的点都应被圈出，如果时间允许应重新测量。用一个新灯泡重复整个实验也能检验可重复性。
8. Extension: Determining the Internal Resistance of a Cell | 拓展：测定电池内阻
The Unit 3 paper occasionally links a basic circuit to the concept of internal resistance. A simple arrangement using a known resistor and a voltmeter across the cell terminals can be applied. As the external load changes, the terminal voltage V decreases due to the voltage drop across the internal resistance r.
单元三试卷有时会将基本电路与内阻的概念联系起来。可使用一个已知电阻和跨接在电池两端的电压表的简单装置。当外部负载变化时，由于内阻 r 上的电压降，端电压 V 会减小。
V = ε – I r
By plotting terminal voltage against current, a straight line with gradient –r and intercept ε is obtained. The open‑circuit voltage (when I = 0) approximates the electromotive force. This classic investigation reinforces the skill of extracting physical quantities from a linear graph.
通过绘制端电压对电流的图像，可得到一条斜率为 –r、截距为 ε 的直线。开路电压（当 I = 0 时）近似为电动势。这个经典探究强化了从线性图中提取物理量的技能。
9. Experiment 3: Oscillation of a Spring–Mass System | 实验三：弹簧-质量系统的振动
The June 2019 exam also featured a mechanical oscillation question. A spring is suspended from a clamp, and slotted masses are added to its end. The time for a number of oscillations (e.g., 20) is recorded using a stopwatch to find the period T.
2019 年 6 月考试还包含了一个机械振动问题。弹簧悬挂在的铁架台上，在其末端增加槽码。使用秒表记录多次（如 20 次）振荡的时间，从而得出周期 T。
The period is related to the mass m and the spring constant k by the formula T = 2π√(m/k). Squaring both sides gives T² = (4π²/k) m, which is a linear relationship between T² and m. The gradient can be used to calculate k.
周期与质量 m 和劲度系数 k 的关系为 T = 2π√(m/k)。两边平方可得 T² = (4π²/k) m，这是 T² 与 m 之间的线性关系。斜率可用于计算 k。
T² = (4π² / k) × m
Care must be taken to keep the oscillations small (small amplitude) so that the motion approximates simple harmonic motion. Starting and stopping the stopwatch at the centre of the oscillation (equilibrium point) reduces reaction‑time error compared to timing at the extremes.
必须注意保持振幅较小，以使运动近似为简谐运动。在振荡中心（平衡点）启动和停止秒表相比在端点计时可减小反应时间误差。
10. Minimising Errors in Timing and Measurement | 减小计时与测量误差
Human reaction time is a major source of random error in oscillation experiments. By measuring the time for multiple oscillations and then dividing by the count, the uncertainty in each individual period is reduced. For 20 oscillations, the period uncertainty becomes about 1/20th of the total timing uncertainty.
人的反应时间是振动实验中随机误差的主要来源。通过测量多次振荡的时间再除以振荡次数，每个单独周期的误差得以减小。对于 20 次振荡，周期的不确定度变为总计时不确定度的大约 1/20。
Systematic errors such as a stopwatch running fast or a metre rule with a zero error should be identified and, if possible, removed by calibration. The paper may ask candidates to describe how to confirm that the spring obeys Hooke’s law before undertaking the oscillation study, by checking extension is proportional to applied load.
系统误差如秒表走快或米尺存在零误差应被识别，并尽可能通过校准消除。试卷可能要求考生描述在进行振动研究之前如何通过验证伸长量与所加载荷成正比来确认弹簧遵循胡克定律。
11. Evaluating Procedures and Suggesting Improvements | 评估实验步骤并提出改进建议
A recurring theme in Unit 3 is the evaluation section, where students must comment on the reliability and limitations of their methods. For the density experiment, one could suggest using a micrometer screw gauge on a regular-shaped part of the object to cross‑check volume, or using a liquid of known density for a comparative flotation method.
单元三反复出现的主题是评估部分，学生必须评论其方法的可靠性和局限性。对于密度实验，可以建议使用千分尺测量物体规则部分的尺寸以交叉检验体积，或使用已知密度的液体进行浮力比较法。
For the electrical experiment, a digital sensor and data logger could replace the manual reading of meters, capturing rapid changes in current and voltage and removing parallax errors. For the spring oscillation, a motion sensor could record displacement, giving a more accurate period from a sinusoidal trace.
对于电学实验，数字传感器和数据记录器可以取代人工读取表计，捕捉电流和电压的快速变化并消除视差误差。对于弹簧振动，运动传感器可以记录位移，从正弦轨迹中给出更精确的周期。
All suggestions must be specific and linked to the stated errors; vague improvements like ‘do it more carefully’ do not receive marks.
所有建议必须具体，并与所述误差相关联；诸如“更仔细地操作”之类的模糊改进不会得分。
12. Exam Tips for AS Physics Unit 3 | AS 物理单元三考试技巧
Success in the practical paper depends on meticulous attention to detail in recording, plotting, and explaining. Always label graph axes with quantity and unit, draw the best-fit line (not dot‑to‑dot), and use a large triangle for gradient calculations. When describing an investigation, use a logical sequence: what is measured, how it is measured, what is kept constant, and how results are used to reach a conclusion.
在实践试卷中取得成功取决于对记录、绘图和解释细节的一丝不苟。始终用物理量和单位标记坐标轴，绘制最佳拟合线（而非点对点连接），并使用大三角形计算斜率。在描述探究过程时，按逻辑顺序进行：测量什么、如何测量、保持哪些量不变、以及如何利用结果得出结论。
Additionally, revising standard laboratory techniques like using a set square to ensure a clamp stand is vertical, or a spirit level for a ramp, strengthens the practical vocabulary needed to earn high marks in the evaluation questions.
此外，复习标准实验室技术，如使用三角尺确保铁架台垂直，或使用水平仪调整斜面，能加强在评估题中获得高分所需的实践词汇。
Finally, allocate time to check for inconsistent significant figures and ensure any calculated uncertainties are expressed to at most one or two significant figures, matching the precision of the instruments.
最后，分配时间检查不一致的有效数字，并确保任何计算出的不确定度最多用一位或两位有效数字表示，与仪器的精密度相匹配。
Published by TutorHao | AS Physics Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
屏轩国际教育cambridge primary/secondary checkpoint, cat4, ukiset,ukcat,igcse,alevel,PAT,STEP,MAT, ibdp,ap,ssat,sat,sat2课程辅导，国外大学本科硕士研究生博士课程论文辅导