IGCSE CCEA Physics: Experimental Skills Guide | IGCSE CCEA 物理：实验操作指南

📚 IGCSE CCEA Physics: Experimental Skills Guide | IGCSE CCEA 物理：实验操作指南

Mastering experimental techniques is essential for success in IGCSE CCEA Physics. This guide covers the fundamental skills you need to plan, carry out, analyse and evaluate experiments confidently, from handling apparatus safely to interpreting graphs and calculating uncertainties.

掌握实验技术对于 IGCSE CCEA 物理考试的成功至关重要。本指南涵盖了你自信地规划、实施、分析和评估实验所需的基本技能，从安全操作仪器到解读图表和计算不确定度。

1. Safety in the Lab | 实验室安全

Always wear eye protection when heating substances, using lasers, or working with stretched wires and springs. Tie back long hair and secure loose clothing. Never run in the lab and report all breakages or spills immediately to your teacher.

在对物质加热、使用激光或处理拉伸的导线和弹簧时，始终佩戴护目镜。扎起长发并系好宽松的衣物。不得在实验室内奔跑，所有破损或溅洒应立即向老师报告。

Electrical circuits must be checked by a teacher before switching on. Use insulated leads and keep voltages low (typically under 12 V) unless instructed otherwise. Do not touch bare wires and always switch off between making adjustments.

电路在通电前必须经老师检查。使用绝缘导线并保持低电压（通常低于 12 V），除非另有指示。不要触碰裸露的导线，调整电路时务必关闭电源。

2. Measurement and Uncertainty | 测量与不确定度

Every measurement carries an uncertainty. For a ruler or a thermometer, the uncertainty is ± half the smallest scale division. For a digital instrument like a stopwatch or ammeter, it is ± the last significant digit, unless the manufacturer claims otherwise.

每次测量都带有不确定度。对于直尺或温度计，不确定度为最小刻度值的一半。对于秒表或电流表等数字仪器，通常为最后一位有效数字的 ± 1，除非制造商另有说明。

Repeat readings reduce random error. If repeat readings are identical, use the reading as recorded. If they differ, calculate the mean and find the range. Express the result as: mean ± half the range (or ± maximum difference from the mean).

重复读数可减小随机误差。如果重复读数相同，则直接使用该读数。如果不同，计算平均值并求出极差。结果表示为：平均值 ± 极差的一半（或 ± 与平均值的最大偏差）。

For example, measuring the length of a pendulum gives: 45.2 cm, 45.4 cm, 45.3 cm. Mean = 45.3 cm; range / 2 = (0.2 cm) / 2 = 0.1 cm. Result: 45.3 ± 0.1 cm.

例如，测量单摆长度得到：45.2 厘米、45.4 厘米、45.3 厘米。平均值 = 45.3 厘米；极差/2 = (0.2 厘米)/2 = 0.1 厘米。结果：45.3 ± 0.1 厘米。

3. Recording Data and Tables | 数据记录与表格

Draw data tables before starting the experiment. Use a pencil and ruler. Each column heading must include the name of the quantity and its unit, separated by a slash, e.g., Time / s, Current / A. Record all raw readings directly into the table – never record on scrap paper.

在实验开始前画好数据表。使用铅笔和直尺。每个列标题必须包括物理量的名称和单位，以斜线分隔，例如时间 / 秒、电流 / 安培。将所有原始读数直接记录在表中——绝不要记在草稿纸上。

Values should be given to the same number of decimal places, consistent with the instrument’s precision. Any calculated quantities (e.g., average time, resistance) should appear in separate columns with their appropriate units.

数值应保留相同的小数位数，与仪器的精度一致。任何计算得出的量（如平均时间、电阻）应出现在单独的列中，并注明合适的单位。

Length / cm	Time t₁ / s	Time t₂ / s	Mean Time / s
20.0	12.45	12.33	12.39
40.0	17.12	17.24	17.18

4. Drawing Graphs | 绘制图表

Use graph paper with a sharp pencil. Plot the independent variable (the one you change) on the horizontal x-axis, and the dependent variable (the one you measure) on the vertical y-axis. Label both axes with the quantity and unit, e.g., Extension / mm.

使用坐标纸和削尖的铅笔。将自变量（你改变的量）放在水平 x 轴，因变量（你测量的量）放在垂直 y 轴。两轴都要标注物理量和单位，例如伸长量 / 毫米。

Choose a scale that makes your points fill at least half the grid in both directions. Scales should be linear and easy to read, like 1, 2, 5, 10 units per cm. Avoid awkward scales such as 3 or 7 units per cm. Draw each data point as a small, neat cross (×) or circle with a dot.

选择能使数据点至少占据网格纸一半面积的标度。标度应为线性且易于读取，例如每厘米 1、2、5、10 个单位。避免使用 3 或 7 这类不便的标度。每个数据点用整洁的小叉号（×）或带点的圆圈标出。

Do not connect point to point. Draw a single best-fit straight line or smooth curve. For a straight line, use a clear ruler. The line should have an even balance of points above and below it, ignoring obvious outliers.

不要将点逐点连接。画一条最佳拟合直线或平滑曲线。对于直线，使用透明的直尺。线上方和下方的点应大致均匀分布，明显的异常点可忽略。

5. Gradient and Intercept | 斜率与截距

If the graph is a straight line passing through the origin, the relationship is directly proportional. The gradient is calculated by selecting two widely spaced points on the line itself (not data points). Use the formula:

如果图形是一条通过原点的直线，则关系为正比。计算斜率时，在拟合线上选取两个相距较远的点（不是原始数据点）。使用公式：

gradient = (y₂ – y₁) / (x₂ – x₁)

斜率 = (y₂ – y₁) / (x₂ – x₁)

Show working clearly on the graph, drawing a large triangle to indicate the rise and run. The units of the gradient are the units of y divided by the units of x; for example, for a voltage–current graph the gradient is in V/A, i.e., ohms.

在图上清楚展示计算过程，画出一个大的三角形来表示纵差和横差。斜率的单位是 y 的单位除以 x 的单位；例如，电压–电流图的斜率单位为 V/A，即欧姆。

The y-intercept is read where the line crosses the y-axis (x = 0). It often has physical meaning, such as the e.m.f. of a cell when the current is zero. State the intercept clearly, including its unit.

y 轴截距是拟合线与 y 轴（x=0）相交处的读数。它通常具有物理意义，例如电流为零时电池的电动势。清晰写出截距，包括其单位。

6. Error Analysis | 误差分析

Systematic errors cause all readings to be shifted by the same amount, e.g., a ruler’s zero mark is worn away, or an ammeter is not zeroed. They affect accuracy but not the spread of readings. Systematic errors cannot be reduced by repeating the experiment; you need to correct the apparatus or method.

系统误差导致所有读数发生相同量的偏移，例如尺子的零刻度磨损，或电流表未调零。它们影响准确度，但不影响读数的离散程度。重复实验不能减小系统误差；需要修正仪器或实验方法。

Random errors arise from unpredictable variations, such as reaction time when using a stopwatch or fluctuations in temperature. Repeating readings and taking the mean reduces their effect. A wider spread of data indicates lower precision.

随机误差来自不可预测的变化，例如使用秒表时的反应时间或温度波动。重复读数并取平均值可减小其影响。数据分布越宽，表明精确度越低。

Anomalies are data points that lie far from the best-fit line. They should be circled and labelled ‘anomalous’. You may repeat that particular measurement if time allows, but do not adjust them to fit the trend. In analysis, anomalous points are excluded from the line of best fit.

异常点是远离最佳拟合线的数据点。应圈出并标注为异常点。如果时间允许，可重测该特定值，但不要为使数据符合趋势而改动它们。在分析时，异常点不纳入最佳拟合线。

7. Key Experiments: Pendulum | 关键实验：单摆

To investigate the relationship between the length L of a pendulum and its period T, set up a clamp stand with a string and small bob. Measure L from the point of suspension to the centre of the bob. Use a protractor to displace the bob by a small angle (less than 10°) and release. Time 10 complete oscillations and divide by 10 to get T. This reduces the uncertainty in the period measurement.

为了研究单摆长度 L 与周期 T 的关系，搭设带有细线和摆球的铁架台。测量从悬挂点到摆球中心的长度 L。用量角器将摆球拉开一个小角度（小于 10°）后释放。记录 10 次全振动的时间，除以 10 得到 T。这样可减小周期测量的不确定度。

Repeat for several lengths. Plot a graph of T² against L. The theory gives T = 2π√(L/g), so T² = (4π²/g) L. A straight line through the origin confirms the relationship. The gradient equals 4π²/g, from which g can be estimated.

对不同的摆长重复实验。绘制 T² 对 L 的图线。理论公式为 T = 2π√(L/g)，因此 T² = (4π²/g) L。一条通过原点的直线可验证该关系。斜率等于 4π²/g，由此可估算 g 值。

8. Key Experiments: Ohm’s Law | 关键实验：欧姆定律

Connect a circuit with a power supply, variable resistor, ammeter in series, and voltmeter in parallel across a fixed resistor. Vary the resistance to obtain at least six pairs of potential difference V and current I readings. Record values in a table.

连接电路：电源、可变电阻器、电流表串联，电压表并联在固定电阻两端。改变电阻器以获取至少六组电势差 V 和电流 I 的读数。将数值记录在表格中。

Plot a graph of V (y-axis) against I (x-axis). For a metallic conductor at constant temperature, the graph is a straight line through the origin, confirming V ∝ I. The gradient gives the resistance R in ohms (Ω).

绘制 V（y 轴）对 I（x 轴）的图线。对于恒温下的金属导体，图形是一条通过原点的直线，证实 V ∝ I。斜率即为电阻 R，单位为欧姆（Ω）。

To measure the resistance of a wire, replace the fixed resistor with the wire. Keep the wire straight and avoid heating. Measure the length and thickness of the wire for resistivity calculations: ρ = RA / L, where A = ¼πd².

要测量导线的电阻，将固定电阻替换为导线。保持导线平直，避免升温。测量导线的长度和粗细以计算电阻率：ρ = RA / L，其中 A = ¼πd²。

9. Key Experiments: Density | 关键实验：密度

Density ρ = mass m / volume V. For a regular solid, measure its dimensions with a ruler or vernier callipers and calculate the volume (e.g., length × width × height for a block). Measure mass using a digital balance. Then compute density.

密度 ρ = 质量 m / 体积 V。对于规则固体，用直尺或游标卡尺测量其尺寸并计算体积（如长方体的长 × 宽 × 高）。用电子天平测量质量。然后计算密度。

For an irregular solid, use the displacement method. Fill a measuring cylinder partly with water, record the initial volume V₁. Carefully lower the solid on a thread, ensuring it is completely submerged, and record the new volume V₂. Volume of solid = V₂ – V₁.

对于不规则固体，使用排水法。在量筒中倒入适量的水，记录初始体积 V₁。用细线小心将固体浸没入水中，记录新体积 V₂。固体的体积 = V₂ – V₁。

For a liquid, measure the mass of an empty beaker, then fill with the liquid and record the new mass. Find the mass of the liquid by subtraction. Pour it into a measuring cylinder to obtain its volume directly. Never measure the mass of the measuring cylinder itself unless you are told to; use a clean, dry beaker instead.

对于液体，测量空烧杯的质量，然后倒入液体并记录新质量。相减得到液体的质量。将其倒入量筒直接读取体积。除非有指示，否则不测量量筒本身的质量；应使用干净干燥的烧杯。

10. Key Experiments: Light – Reflection | 关键实验：光的反射

Place a plane mirror upright on a sheet of white paper. Draw its outline. Use a ray box to shine a single ray of light at the mirror. Mark the incident ray and the reflected ray with two crosses each. Remove the mirror and draw the rays and the normal (a line perpendicular to the mirror surface at the point of incidence).

将平面镜竖直放在一张白纸上，描出其轮廓。使用光线盒射出一束单色光到镜面上。用两个叉号标出入射光线和反射光线的路径。移开镜子，画出光线并画出法线（在入射点处垂直于镜面的直线）。

Measure the angle of incidence i and the angle of reflection r with a protractor. Record angles in a table. Repeat for several different incident angles. You should find that i = r within experimental uncertainty, confirming the law of reflection.

用量角器测量入射角 i 和反射角 r。将角度记录在表格中。对不同入射角重复实验。你应该会在实验不确定度范围内发现 i = r，从而验证反射定律。

Precision improves if the rays are narrow and the crosses are placed far apart. Also, draw the ray lines through the centre of the cross marks, which represents the position of the light ray.

如果光线较窄且叉号相距较远，精确度会提高。同时，绘制的光线应穿过叉号连线的中心，以代表光线的实际位置。

11. Evaluation and Improvement | 评估与改进

A good evaluation identifies specific sources of error, not just general statements like ‘the stopwatch is inaccurate’. For the pendulum, a major source of error is the reaction time in starting and stopping the stopwatch. You can improve reliability by timing multiple oscillations, using a light gate, or by repeating and averaging.

好的评估能指明具体的误差来源，而非仅泛泛而谈‘秒表不准确’。对于单摆实验，主要的误差来源是启动和停止秒表时的反应时间。可通过计时多个全振动、使用光门，或多次重复取平均值来提高可靠性。

Suggest realistic improvements: ‘Use a fiducial marker (e.g., a vertical pin) at the centre of the swing so that timing begins and ends exactly when the string passes the marker.’ Also, check that the clamp stand is stable and that the bob oscillates in a single plane.

提出现实的改进建议：’在摆动中央使用基准标记（例如垂直的细针），这样当细绳经过标记时可精确开始和停止计时。’ 此外，要确保铁架台稳定，摆球在单一平面内摆动。

Always comment on whether the data supports the hypothesis. If the line is straight and passes through the origin, the relationship is proportional. If there is a small intercept, suggest a possible cause, such as a systematic error in the zero position of a ruler.

总是评论数据是否支持假设。如果图线是直线且通过原点，则两者成正比。如果存在截距，提出可能的原因，例如尺子零位存在系统误差。

12. Using Common Apparatus | 常用仪器使用

Vernier callipers: Use them to measure inner and outer diameters and depths. Read the main scale to the nearest millimetre and then find the vernier mark that best aligns with the main scale. Add the vernier reading to the main scale. A typical uncertainty is ±0.01 cm.

游标卡尺：用于测量内径、外径和深度。先读取主尺上最近的毫米值，再找到与主尺刻度线最对齐的游标刻度线。将游标读数加到主尺读数上。典型不确定度为 ±0.01 厘米。

Micrometer screw gauge: It provides even finer measurements (typically ±0.001 cm). Check for zero error before use by closing the gap gently and reading the scale. If there is a zero error, record it and subtract from all subsequent readings.

螺旋测微计：提供更精密的测量（通常为 ±0.001 厘米）。使用前检查零误差，轻轻合拢测砧后读数。如果有零误差，记录下来，并在后续所有读数中减去该值。

Multimeters: Used to measure current (in series) and voltage (in parallel). Always start on the highest range to avoid damaging the meter. For resistance measurements, ensure the component is disconnected from any power source.

万用表：用于测量电流（串联）和电压（并联）。始终先从最高量程开始，以避免损坏电表。测量电阻时，确保待测元件已脱离任何电源。

Stopwatch: Reaction time uncertainty is typically ±0.2 s. For better precision with short time intervals, use a light gate connected to a data logger, which can measure times to within ±0.001 s or better.

秒表：反应时间不确定度通常为 ±0.2 秒。为更精确测量短时间间隔，可使用连接数据记录仪的光门，其计时精度可达 ±0.001 秒甚至更佳。

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IGCSE CCEA Physics: Experimental Skills Guide | IGCSE CCEA 物理：实验操作指南