📚 A-Level Physics Unit 5: Experimental Investigation Insights from Jun22 Mark Scheme | A-Level 物理 Unit 5：2022 年 6 月评分方案实验探究解读
The June 2022 mark scheme for A-Level Physics Unit 5 provides valuable insight into how practical investigations are assessed. By understanding the marking criteria, students can refine their experimental design, data handling, and evaluation skills. This article breaks down the key expectations revealed in the mark scheme, covering planning, measurements, graphical analysis, uncertainty treatment, and critical assessment — all essential for scoring high marks in the investigation component.
2022 年 6 月 A-Level 物理 Unit 5 的评分方案为实验探究的评分方式提供了宝贵的参考。理解评分标准有助于学生优化实验设计、数据处理和评估能力。本文分解了评分方案中揭示的关键要求，涵盖实验规划、测量、图像分析、不确定度处理以及批判性评价 —— 这些都是在探究题中获得高分必不可少的要素。
1. Planning the Investigation | 实验规划
The mark scheme emphasises that a clear, logical plan is the foundation of a successful investigation. You must identify the independent, dependent, and control variables before describing the procedure. The plan should include a labelled diagram of the apparatus, with all instruments specified. Marks are awarded for choosing appropriate equipment and explaining why it is suitable — for instance, using a vernier calliper for small lengths or a digital voltmeter for precise potential difference readings.
评分方案强调，清晰、有逻辑的实验计划是成功探究的基础。在描述步骤之前，必须明确自变量、因变量和控制变量。计划中应包括带标注的实验装置图，并标明所有仪器。选择恰当的设备并解释其适用性，能够获得分数 —— 例如，用游标卡尺测量小长度，或用数字电压表获取精确的电势差读数。
You should also mention pilot experiments if necessary, and state how you would minimise risks (e.g., keep voltages low, wear goggles). The procedure must be sequential and reproducible. Simply listing steps is not enough; you must justify each decision.
必要时还应提到试探性实验，并说明如何降低风险（如使用低电压、佩戴护目镜）。步骤必须具有顺序性和可重复性。仅仅罗列步骤是不够的，必须为每个决定提供理由。
2. Identifying and Controlling Variables | 识别与控制变量
The mark scheme expects candidates to explicitly state which variables are to be kept constant and how. For example, if investigating how the period of a pendulum depends on length, you must control mass and amplitude. The method of control must be practical: using the same bob, releasing from a small angle (< 10°), and measuring length to the centre of mass.
评分方案期望考生明确说明哪些变量需要保持恒定以及如何控制。例如，如果探究单摆周期与摆长的关系，必须控制质量与振幅。控制方法必须切实可行：使用同一个摆球，从小于 10° 的小角度释放，并测量到质心的长度。
Where there are multiple control variables, use a table to list them. This shows systematic thinking. The mark scheme rewards candidates who link each variable to a physical principle — for instance, controlling temperature in resistance experiments because resistivity depends on temperature.
当存在多个控制变量时，用表格列出来，这体现了系统化思维。评分方案奖励那些将每个变量与物理原理联系起来的考生 —— 例如，在电阻实验中控制温度，因为电阻率与温度相关。
- Independent variable: the one you change (e.g., length of wire) / 自变量：你改变的变量（如导线长度）
- Dependent variable: the one you measure (e.g., resistance) / 因变量：你测量的变量（如电阻）
- Control variables: kept constant (e.g., cross-sectional area, temperature) / 控制变量：保持恒定（如截面积、温度）
3. Selecting Suitable Apparatus and Range | 选择合适的仪器与量程
Marks are allocated for choosing instruments with the correct resolution and range. For a current measurement expected around 0.5 A, a 0–1 A ammeter with 0.01 A resolution is better than a 0–10 A ammeter with 0.1 A resolution. The mark scheme expects you to explain why the resolution and range are fit for purpose, and how they affect the percentage uncertainty.
选择具有正确分辨率和量程的仪器能够得分。对于预计 0.5 A 左右的电流测量，0–1 A、分辨率为 0.01 A 的电流表优于 0–10 A、分辨率为 0.1 A 的电流表。评分方案期望你解释分辨率和量程为何适合需求，以及它们如何影响百分比不确定度。
| Instrument / 仪器 | Typical Resolution / 典型分辨率 | Good for / 适用场景 |
|---|---|---|
| Metre ruler / 米尺 | 1 mm | Lengths > 0.5 m / 大于 0.5 m 的长度 |
| Vernier calliper / 游标卡尺 | 0.01 mm (0.1 mm for some) / 0.01 mm (部分 0.1 mm) | Diameter, thickness < 10 cm / 直径、厚度小于 10 cm |
| Micrometer / 千分尺 | 0.001 mm (0.01 mm for some) / 0.001 mm (部分 0.01 mm) | Wire diameter, small gaps / 导线直径、小间距 |
| Digital multimeter / 数字万用表 | 0.001 V / 0.01 mA depending on range / 取决于量程 | Voltage, current, resistance / 电压、电流、电阻 |
Marks are also given for repeating readings and taking averages to reduce random error. The plan should specify the number of repeats (at least 5–6 data points, with 3 repeats each).
重复读数并取平均值以减小随机误差同样可以得分。计划中应明确重复次数（至少 5–6 个数据点，每个点重复 3 次读数）。
4. Data Recording and Significant Figures | 数据记录与有效数字
The Jun22 mark scheme penalises inconsistent significant figures and missing units. All raw data must be recorded in a well-structured table with headings that include the quantity and its unit, separated by a forward slash (e.g., Length / m). Instrument readings should be recorded to the full precision of the instrument, and derived quantities should reflect the least precise input.
2022 年 6 月的评分方案对不一致的有效数字和缺失的单位进行扣分。所有原始数据必须记录在结构清晰的表格中，表头需包含物理量及其单位，并用斜线分隔（如 Length / m）。仪器读数要记录到仪器的全部精度，而导出量的有效数字应反映最不精确的输入值。
For example, if a voltmeter gives 2.50 V, you must write 2.50, not 2.5. If current is measured as 0.30 A, the resistance V/I = 8.3 Ω, not 8.333 Ω, because the current has only 2 significant figures. The mark scheme expects you to apply the rules consistently.
例如，若电压表显示 2.50 V，必须记作 2.50，而非 2.5。如果电流测量值为 0.30 A，电阻 V/I = 8.3 Ω，而非 8.333 Ω，因为电流只有两位有效数字。评分方案要求你始终如一地应用这些规则。
5. Graphical Skills: Axes, Scales, and Plotting | 图像技巧：坐标轴、刻度与描点
The mark scheme demands that graphs are plotted on proper graph paper with both axes labelled (quantity/unit). Scales must be linear, using at least half the paper, and not using awkward multiples (like 3, 7). Points should be plotted as small crosses or dots with circles, and they must be accurate to within half a small square.
评分方案要求将图像绘制在恰当的坐标纸上，两条坐标轴均需标注（物理量 / 单位）。刻度必须线性，至少占据半张纸，且不应使用别扭的倍数（如 3 倍、7 倍）。数据点应以小十字或带圈圆点的形式准确描出，精度需在半小格以内。
The mark scheme often specifies that you need to draw either a line of best fit or a curve. If the relationship is expected to be linear, draw a single straight line through the plotted points, showing balanced scatter. Do not force the line through the origin unless the physics demands it and it is justified.
评分方案通常会指定需要绘制最佳拟合线或曲线。若预期关系为线性，应画一条穿过数据点的直线，体现均匀的离散分布。除非物理理论要求且经合理判断，否则不应强制直线通过原点。
An example: when plotting V against I for a fixed resistor, the line should pass through the origin, but for a filament lamp, it should not. Always refer to the expected physical relationship.
示例：对于固定电阻的 V-I 图像，直线应通过原点；但对于灯丝灯泡，则不应通过原点。始终参考预期物理关系。
6. Determination of Gradient and Intercept | 斜率和截距的确定
The mark scheme rewards using a large triangle when calculating gradient, with coordinates taken directly from the line of best fit (not data points). Show that the triangle covers at least half the line, and read the coordinates to the precision of the scale.
评分方案鼓励在计算斜率时使用大三角形，坐标应直接从最佳拟合线上读取（而非数据点）。需显示三角形至少覆盖直线的一半长度，并以刻度精度读取坐标。
Gradient is calculated as:
slope = (y₂ – y₁) / (x₂ – x₁)
and should be stated with appropriate units. If the intercept is required, read it from the graph where the line crosses the axis. The mark scheme will check that your intercept matches your drawn line.
斜率计算公式为：
斜率 = (y₂ – y₁) / (x₂ – x₁)
并应带有恰当的单位。若需要截距，则从图中直线与坐标轴的交点读取。评分方案将检查截距是否与你绘制的直线相吻合。
Sometimes the mark scheme asks for the intercept to be determined from a rearranged equation, e.g., y = mx + c. You must quote it with units. Do not forget that the intercept has physical meaning — for example, in a pendulum T² vs L graph, the intercept might indicate a systematic error in length.
有时评分方案要求从重新排列的方程中确定截距，如 y = mx + c。你必须带单位给出截距。不要忘记截距具有物理意义 —— 例如，在单摆 T²-L 图像中，截距或许表示长度测量中的系统误差。
7. Handling Uncertainties in Graphs | 图像中的不确定度处理
Uncertainty analysis is heavily weighted in the Jun22 mark scheme. For scatter in data, you must draw best-fit and worst-fit lines (or use maximum and minimum gradient lines). The mark scheme typically instructs candidates to draw a second line that represents the steepest or shallowest plausible fit.
不确定度分析在 2022 年 6 月的评分方案中权重很高。对于数据的离散性，必须绘制最佳拟合线和最差拟合线（或使用最大梯度和最小梯度线）。评分方案通常指导考生再画一条表示最陡或最平缓合理拟合的直线。
The uncertainty in gradient is given by:
Δslope = |slopeₘₐₓ – slopeₘᵢₙ| / 2
and the percentage uncertainty is (Δslope / slope) × 100%. Similar treatment applies to the intercept. The mark scheme penalises candidates who give absurdly low uncertainties, e.g., <1% for analogue instruments.
梯度的不确定度由下式给出：
Δ斜率 = |斜率ₘₐₓ – 斜率ₘᵢₙ| / 2
百分比不确定度为 (Δ斜率 / 斜率) × 100%。截距的处理方法类似。评分方案会扣罚给出不合理低不确定度的考生，例如对模拟仪器声称 <1% 的不确定度。
8. Combining Uncertainties | 不确定度的合成
When using a derived quantity from measured values, you may need to combine absolute or percentage uncertainties. The Jun22 mark scheme expects candidates to add absolute uncertainties when summing (e.g., total length L = L₁ + L₂ → ΔL = ΔL₁ + ΔL₂) and to add percentage uncertainties when multiplying/dividing (e.g., R = V/I → %ΔR = %ΔV + %ΔI).
当使用测量值计算导出量时，你可能需要合成绝对或百分比不确定度。2022 年 6 月的评分方案期望考生在相加时合成绝对不确定度（例：总长度 L = L₁ + L₂ → ΔL = ΔL₁ + ΔL₂），而在乘除时合成百分比不确定度（例：R = V/I → %ΔR = %ΔV + %ΔI）。
For a power law, e.g., v = k Tⁿ, the percentage uncertainty in v is n times the percentage uncertainty in T. The mark scheme will award marks for correctly propagating uncertainties to the final result, and for comparing experimental value with an accepted value using percentage difference.
对于幂函数，如 v = k Tⁿ，v 的百分比不确定度是 T 百分比不确定度的 n 倍。评分方案会对正确传递不确定度至最终结果的做法给分，并对利用百分比差异比较实验值与公认值的行为给分。
9. Identifying and Minimising Errors | 识别并减小误差
Marks are given for distinguishing between random and systematic errors. Random errors cause readings to scatter symmetrically about the true value and can be reduced by taking more repeats. Systematic errors (e.g., zero error on a micrometer, parallax error when reading a voltmeter) shift all readings in one direction and cannot be averaged out; they require calibration or technique improvement.
区分随机误差与系统误差可以得分。随机误差导致读数对称地散布在真值周围，可通过增加重复次数来减小。系统误差（如千分尺的零误差、读电压表时的视差）使所有读数朝同一方向偏移，无法通过平均消除；需要校准或改进技术。
The Jun22 mark scheme likes to see specific suggestions for error reduction: use a set square to reduce parallax, ensure the rule is vertical using a plumb line, clean contacts to reduce contact resistance, etc. Generic statements like “use more accurate instruments” earn little, unless you specify which instrument and why.
2022 年 6 月的评分方案钟爱具体的误差减小建议：用三角尺减小视差，用铅垂线确保尺子垂直，清洁触点以降低接触电阻等。像“使用更精确的仪器”这样笼统的表述得分很低，除非你具体说明哪种仪器及原因。
10. Drawing Valid Conclusions | 得出有效结论
A conclusion must be directly supported by the data. The mark scheme expects you to state whether the relationship is proportional (straight line through origin) or linear (straight line with intercept), and to quote the equation of the line with uncertainties. For example: “The period squared is directly proportional to the length, with gradient 4.03 ± 0.15 s²m⁻¹, consistent with the theoretical value 4.02 s²m⁻¹ from g = 9.81 ms⁻².”
结论必须直接得到数据支持。评分方案期望你陈述关系是成正比的（过原点的直线）还是线性的（有截距的直线），并给出带不确定度的直线方程。例如：“周期的平方与摆长成正比，斜率为 4.03 ± 0.15 s²m⁻¹，与由 g = 9.81 ms⁻² 得出的理论值 4.02 s²m⁻¹ 相符。”
If there is a discrepancy, the mark scheme wants you to comment on it using uncertainties. If the percentage difference between experiment and theory is less than the experimental percentage uncertainty, the results are considered consistent. Otherwise, you must suggest systematic errors that could account for the discrepancy.
若存在差异，评分方案希望你能用不确定度加以评述。如果实验与理论的百分比差异小于实验百分比不确定度，则结果被视为一致。否则，必须提出可能造成差异的系统误差。
11. Evaluation of the Experiment | 实验评估
The evaluation section demands that you critically appraise your own design and results. The Jun22 mark scheme reminds candidates to discuss limitations, such as difficulty in maintaining steady temperature, fluctuations in power supply, timing errors for short intervals, or friction effects. You should explain how each limitation affects the result (makes the gradient too steep, increases scatter, etc.).
评估部分要求你对自身的设计和结果进行批判性评价。2022 年 6 月的评分方案提醒考生讨论局限性，如难以保持恒定温度、电源波动、短时程的计时误差或摩擦效应。你应说明每个局限性如何影响结果（使斜率过陡、增加离散性等）。
Most importantly, suggest realistic improvements that directly address these limitations. If timing was difficult, use a light gate or motion sensor. If thermal equilibrium was not reached, wait longer or use a water bath. The mark scheme penalises vague suggestions, so be specific and show how each improvement reduces the identified error.
最重要的是，提出切实可行的改进方法直接应对这些局限性。如果计时困难，可使用光闸或运动传感器。若未达到热平衡，可等待更长时间或使用水浴。评分方案惩罚含糊的建议，因此务必具体，并展示每项改进如何减小已识别的误差。
| Limitation / 局限 | Effect / 影响 | Improvement / 改进 |
|---|---|---|
| Parallax when reading ammeter / 读电流表时的视差 | Systematic off-set / 系统偏移 | Use digital meter with anti-parallax mirror / 使用带防视差镜的数字仪表 |
| Heat loss to surroundings / 向环境散热 | Gradient reduced / 斜率减小 | Insulate container, use lid / 给容器隔热，使用盖子 |
| Zero drift in electronic sensor / 电子传感器零点漂移 | Intercept changed / 截距改变 | Re-zero between readings / 每次读数间重新调零 |
12. Common Pitfalls and Examiner Advice | 常见错误与考官建议
The Jun22 mark scheme reveals frequent mistakes that cost marks: forgetting to specify the volume or concentration in chemical-related physics experiments, not recording repeat readings in the table, using computer-generated graphs that lack scale labels, and quoting a final value to far more significant figures than justified. Examiners also caution against drawing a ‘dot-to-dot’ line instead of a line of best fit.
2022 年 6 月的评分方案揭示了经常导致失分的错误：在与化学相关的物理实验中忘记指明体积或浓度、未在表格中记录重复读数、使用计算机生成的图像却缺少刻度标签、以及引用过多有效数字的最终值。考官还提醒，不要画“点对点”连线，而应画最佳拟合线。
Another pitfall is misidentifying the dependent variable; make sure it is the one you measure as a response. Also, in planning, do not just say “measure the length”. Explain how, e.g., “measure the length of the wire between the crocodile clips using a metre ruler, ensuring the rule is parallel to the wire”. Detailed descriptions give access to higher marks.
另一个陷阱是错误识别因变量；务必将其设为你作为响应而测量的那个量。此外，在规划中，不要只说“测量长度”。要解释如何测量，例如“用米尺测量鳄鱼夹之间的导线长度，确保尺子与导线平行”。详细的描述有助于获得更高的分数。
Published by TutorHao | 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