IB & Edexcel Physics: Guide to Experimental Skills | IB 与 Edexcel 物理：实验操作指南

📚 IB & Edexcel Physics: Guide to Experimental Skills | IB 与 Edexcel 物理：实验操作指南

Mastering experimental skills is central to success in both IB Physics and Edexcel Physics. Whether you are designing an investigation, taking measurements, or evaluating data, a systematic approach built on sound methodology, uncertainty analysis, and critical reflection will raise the quality of your practical work and your final grades.

掌握实验技能是学好 IB 物理和 Edexcel 物理的核心。无论你在设计探究、进行测量，还是分析数据，一套建立在实际方法、不确定度分析和批判性反思基础上的系统流程，都能大幅提升你的实验质量和最终成绩。

1. Understanding Variables and Control | 理解变量与控制

Every experiment involves independent, dependent and controlled variables. The independent variable is the one you deliberately change; the dependent variable is what you measure as a result; controlled variables are kept constant to ensure a fair test.

每个实验都涉及自变量、因变量和控制变量。自变量是你有意改变的物理量；因变量是你对应测量的结果；控制变量则必须保持不变，以保证实验的公平性。

For IB Internal Assessment (IA) and Edexcel core practicals, you must explicitly state how you will measure and vary the independent variable, and list at least three controlled variables with the method used to keep them constant.

在 IB 内部评估（IA）和 Edexcel 核心实验中，你必须明确说明如何测量和改变自变量，并列出至少三个控制变量及其保持不变的方法。

For example, in an experiment to measure the period of a pendulum, length is the independent variable, period is the dependent variable, while mass, amplitude (small angle) and air currents must be controlled.

例如，在测量单摆周期的实验中，摆长是自变量，周期是因变量，而摆锤质量、振幅（小角度）和气流都必须控制。

2. Measurement Tools and Precision | 测量工具与精密度

Choose instruments that give adequate precision for your investigation. A metre rule (±1 mm) is suitable for lengths above 10 cm, but a vernier caliper (±0.1 mm or ±0.02 mm) or micrometer screw gauge (±0.01 mm) should be used for smaller dimensions where greater precision is required.

根据探究需要选择精密度合适的仪器。米尺（±1 mm）适用于超过 10 cm 的长度测量，但需要更高精度的较小尺寸则应当使用游标卡尺（±0.1 mm 或 ±0.02 mm）或螺旋测微计（±0.01 mm）。

Digital instruments usually have a quoted precision of ± the smallest displayed unit, while analogue instruments require you to estimate the reading to half the smallest scale division. Always record the absolute uncertainty of each measuring device.

数字式仪器的精密度通常表示为 ± 最小显示单位的 1 倍，而模拟式仪器则需要估读到最小分度值的一半。每次都要记下每个测量设备的绝对不确定度。

Repeated measurements reduce random error. Calculate the mean and use the half-range (max−min)/2 or standard deviation to estimate the uncertainty in the mean, depending on the level required by your syllabus.

重复测量可以减小随机误差。计算平均值，并根据课程要求，使用半区间（最大值−最小值）/2 或标准偏差来估计平均值的误差。

3. Uncertainties: Absolute, Fractional and Percentage | 不确定度：绝对、相对和百分比

Absolute uncertainty (Δx) is the estimate of the range within which the true value lies, expressed in the same units as the measurement. For a single reading, it might be half the smallest scale division; for a digital reading, ± the resolution.

绝对不确定度（Δx）是对真值所在范围的估计，单位与测量值相同。单次读数时，它通常是仪器最小分度值的一半；数字读数则为 ± 分辨率。

Fractional uncertainty is Δx / x and percentage uncertainty is (Δx / x) × 100%. These relative forms allow you to compare the quality of different measurements.

相对不确定度是 Δx / x，百分比不确定度是 (Δx / x) × 100%。这些相对形式可以比较不同测量结果的质量。

When stating a result, always give it as (mean ± absolute uncertainty) with the correct unit, e.g., T = 1.56 ± 0.02 s. The uncertainty should normally be rounded to 1 or 2 significant figures and the mean to the same decimal place.

记录结果时，始终采用（平均值 ± 绝对不确定度）格式，并写上正确单位，例如 T = 1.56 ± 0.02 s。不确定度通常保留 1 或 2 位有效数字，平均值与之保持相同的小数位数。

4. Recording Data and Designing Tables | 数据记录与表格设计

All raw data should be recorded in a clearly labelled table. The table title describes what is measured, and each column header must include the quantity, symbol, unit and, where appropriate, the absolute uncertainty.

所有原始数据都应记录在清晰标记的表格中。表格标题要说明测量内容，每一列的抬头必须包含物理量名称、符号、单位，并在合适时指明绝对不确定度。

Length L / cm	Time for 10 swings t₁₀ / s	Period T / s
50.0 ± 0.1	14.12, 14.20, 14.18	1.412 ± 0.004

Use the same precision for all readings in a column and do not leave empty cells. If a value is to be calculated later, leave an empty column or mark it as “calculated” – raw data and processed data should be separated where possible.

同一列中所有读数的精度要保持一致，不要留空格。如果需要后续计算，可单独留出一列或标注“计算值”——原始数据与处理后数据应尽可能分开。

5. Plotting Graphs and Drawing Lines of Best Fit | 绘制图形与最佳拟合线

Choose scales that use more than half the graph paper in each direction and are easy to read (e.g., 1, 2, 5 or 10 units per cm). Do not use awkward scales like 3 or 7 units per cm. Label each axis with quantity and unit, e.g., “Distance d / m”.

坐标比例要尽量占到坐标纸各方向的一半以上，且便于读数（如每厘米代表 1、2、5 或 10 个单位）。避免使用 3 或 7 这样难读的比例。每个轴都要标出物理量和单位，如“Distance d / m”。

Plot points with fine crosses or dots with circles; do not use large blobs. After plotting, draw a line of best fit – a single straight line or a smooth curve – that passes through as many points as possible with roughly equal numbers of points on either side.

数据点用细小的十字或加点圆圈标记，不要画成大的涂鸦。描点后，画出最佳拟合线（一条直线或平滑曲线），使其尽可能穿过大部分点，并使线两边的点数大致相等。

For linear relationships, use a clear transparent ruler. If the line does not go through the origin, do not force it. The best-fit line helps you determine the gradient and intercept with their uncertainties.

对于线性关系，用透明直尺画线。如果最佳拟合线不通过原点，不要强行拉伸。利用最佳拟合线可以求出斜率和截距以及它们的不确定度。

6. Linearization Techniques | 线性化技术

Many physical relationships are non-linear, but you can transform them into a straight-line form for easier analysis. Re-arrange the equation into y = mx + c and decide what to plot on each axis.

许多物理关系是非线性的，但可以将其变换成直线形式以便分析。将方程整理成 y = mx + c 的形式，并决定每个轴应画的物理量。

For example, T = 2π√(L/g) can be squared to give T² = (4π²/g) L. Plotting T² against L yields a straight line through the origin, with gradient = 4π²/g.

例如，T = 2π√(L/g) 可平方为 T² = (4π²/g) L。以 T² 对 L 作图会得到一条过原点的直线，斜率为 4π²/g。

Common transformations include: y vs x², y vs 1/x, ln y vs ln x (for power laws), and ln y vs x (for exponential decay). Always choose the linearisation suggested by your theory, and check that the plotted points lie on a straight line.

常见的变换包括：y 对 x²、y 对 1/x、ln y 对 ln x（用于幂律关系），以及 ln y 对 x（用于指数衰减）。始终按照理论建议进行线性化，并检验描点是否确实落在一条直线上。

7. Determining Gradients and Intercepts | 求斜率和截距

Use the best-fit line, not data points, to calculate the gradient. Select two points on the line that are far apart (at least half the length of the line) and clearly labelled. Use the formula:

用最佳拟合线而不是原始数据点来计算斜率。在线上选取两个相距较远的点（至少跨过线长的一半），并清晰标出。使用公式：

gradient = (y₂ − y₁) / (x₂ − x₁)

斜率 = (y₂ − y₁) / (x₂ − x₁)

The intercept is read directly from the axis where x = 0, or for lines not crossing the y-axis, it can be calculated using y = mx + c with one point on the line.

截距直接从 x = 0 处对应的坐标轴上读取；对于不穿过 y 轴的直线，可利用线上一点代入 y = mx + c 求得。

To find the uncertainty in gradient, draw lines of maximum and minimum slope (steepest and shallowest) that still pass through all error bars. The uncertainty Δm = (m_max − m_min) / 2.

要求斜率的不确定度，画出能穿过所有误差棒的最大斜率线和最小斜率线（最陡和最平缓）。不确定度 Δm = (m_max − m_min) / 2。

8. Error Propagation in Calculations | 计算中的误差传递

When you combine measurements, uncertainties propagate through the calculation. The rules are straightforward:

当你组合测量结果时，不确定度会在计算中传递。规则很直观：

For addition or subtraction: Δz = Δx + Δy (add absolute uncertainties)

加减法时：Δz = Δx + Δy（绝对不确定度相加）
For multiplication or division: (Δz / z) = (Δx / x) + (Δy / y) (add fractional or percentage uncertainties)

乘除法时：(Δz / z) = (Δx / x) + (Δy / y)（相对或百分比不确定度相加）
For power law z = k xⁿ: (Δz / z) = |n| (Δx / x)

幂函数 z = k xⁿ 时：(Δz / z) = |n| (Δx / x)

If a quantity is raised to a power, multiply the percentage uncertainty by the power. In IB and Edexcel, you are expected to propagate uncertainties for at least one calculated quantity.

某量被乘方时，将百分比不确定度乘以指数。在 IB 和 Edexcel 中，你至少要对一个计算量进行不确定度传递。

For example, if density ρ = m / V and Δm = 0.1 g, m = 10.0 g, ΔV = 0.5 cm³, V = 5.0 cm³, then %Δρ = (0.1/10.0 + 0.5/5.0) × 100% = 1% + 10% = 11%.

例如，密度 ρ = m / V，Δm = 0.1 g，m = 10.0 g，ΔV = 0.5 cm³，V = 5.0 cm³，则 %Δρ = (0.1/10.0 + 0.5/5.0) × 100% = 1% + 10% = 11%。

9. Evaluating the Experiment | 实验评估

A strong evaluation goes beyond saying “human error”. Identify specific systematic and random errors in your method. Systematic errors (e.g., zero error on a meter, parallax error) affect accuracy; random errors (e.g., reaction time, fluctuations) affect precision.

优秀的评估不是只说“人为误差”，而应明确指出方法中具体的系统误差和随机误差。系统误差（如仪表零点误差、视差）影响准确度；随机误差（如反应时间、读数波动）影响精密度。

For IB IA, you must comment on the size of error bars and whether the intercept falls within the expected range. Compare your result to an accepted value using percentage difference: |(experimental−accepted) / accepted| × 100%.

IB 内部评估中，你必须评论误差棒的大小，以及截距是否落在预期范围内。将实验结果与公认值比较时使用百分比差异：|(实验值−公认值) / 公认值| × 100%。

Discuss whether the line of best fit passes through all error bars. If not, identify which point may be anomalous and propose a physical reason. Suggest realistic improvements, not just “use more precise instruments” – for instance, use a fiducial marker to improve timing accuracy, or shield equipment from drafts.

讨论最佳拟合线是否穿过所有误差棒。如果没有，找出哪个点可能是异常点，并提出物理原因。提出切实的改进措施，而不只是“使用更精密的仪器”——例如使用定位标记来提高计时精度，或给设备加防风罩。

10. Safety Guidelines | 安全指南

Although many classroom experiments appear low-risk, safety must always be documented. Identify hazards (e.g., hot objects, sharp edges, electrical supplies, falling masses) and state the precautions you took.

尽管许多课堂实验看起来风险不高，但安全因素必须记录在案。识别危险（如高温物体、锋利边缘、电源、下落的砝码），并说明你采取了哪些预防措施。

For example, when investigating Newton’s second law using a trolley and masses, secure the pulley and ensure the landing area is clear to avoid falling masses hitting feet. When using springs, wear safety glasses to prevent eye injury if a spring snaps.

例如，使用小车和砝码研究牛顿第二定律时，要固定滑轮并确保落地区域畅通，以防砝码砸到脚。使用弹簧时，要戴上护目镜以免弹簧突然断裂伤眼。

Edexcel core practical worksheets often include a specific safety section. IB moderators expect you to show awareness of ethical and environmental considerations as well, such as disposing of salt solutions or broken glass responsibly.

Edexcel 核心实验任务单常常包含专门的安全部分。IB 评分员还希望你能展现对环境与伦理因素的认识，例如妥善处理盐溶液或碎玻璃。

11. Practical Tips for IB IA and Edexcel Core Practicals | IB 内部评估与 Edexcel 核心实验的实战建议

In IB Physics, your IA requires a personal engagement criterion: show initiative by choosing a variant of a standard experiment or investigating a context that genuinely interests you. Keep your research question focused – one independent variable, one dependent variable – and justify the range of values you intend to measure.

在 IB 物理中，内部评估要求体现个人参与度：你可以选择一个标准实验的变体，或者探究自己真正感兴趣的背景，以展示主动性。研究问题要聚焦（单个自变量、单个因变量），并说明你打算测量数值范围的合理性。

For Edexcel Core Practicals, you must know the key apparatus and methods for each required practical. Revision should include how to minimise uncertainties, what graph you plot, and how the gradient relates to the physical constant (e.g., g from a pendulum, resistivity from a wire).

对于 Edexcel 核心实验，你需要掌握每个规定实验的关键仪器和方法。复习时应包括如何减少不确定度、画出何种图形，以及斜率如何与物理常数挂钩（例如通过单摆求 g，通过导线求电阻率）。

In both courses, always record raw data immediately in ink and note any anomalous conditions. Using a smartphone in slow‑motion mode can greatly improve time measurements for fast events. Never ignore a safety checklist.

在这两门课程中，都要立即用墨水笔记录原始数据，并注明任何异常情况。使用手机的慢动作模式可以大幅改善快速事件的时间测量。永远不要忽视安全检查表。

Finally, allocate time for processing data and writing the evaluation. A well‑drawn graph with error bars and clear uncertainty calculations often carries more weight than a long list of minor improvements.

最后，要为数据分析和写评估留出时间。一幅带有误差棒且不确定度计算清晰的良好图表，往往比罗列一长串细小的改进建议更能得分。

Published by TutorHao | Physics Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）

IB & Edexcel Physics: Guide to Experimental Skills | IB 与 Edexcel 物理：实验操作指南