Year 10 Cambridge Physics: Practical Assessment Essentials | 剑桥10年级物理：实验考核要点

📚 Year 10 Cambridge Physics: Practical Assessment Essentials | 剑桥10年级物理：实验考核要点

Practical work lies at the heart of Cambridge IGCSE Physics. Year 10 students must become confident in designing, carrying out, analysing and evaluating experiments. This article pulls together the key skills and concepts examiners look for in practical assessments, from safety to graph plotting and error analysis.

实验操作是剑桥IGCSE物理的核心。10年级学生必须能自信地设计、开展、分析和评估实验。本文汇总了考官在实践考核中重点关注的技能与概念，涵盖从安全规范到绘图和误差分析的全过程。

1. Safety First in the Lab | 实验室安全第一

Always wear eye protection when heating substances, using acids, or working with stretched wires or springs under tension. Tie long hair back and tuck in loose clothing to avoid catching on apparatus.

在对物质加热、使用酸液，或者操作处于拉伸状态的金属丝或弹簧时，务必佩戴护目镜。将长发束起，把宽松衣物塞好，以免被仪器钩住。

Handle hot objects with tongs or heat-proof gloves. Never leave a Bunsen burner on the yellow safety flame when not in use; always turn it to the blue flame only when heating, and turn it off immediately afterwards.

使用坩埚钳或隔热手套拿取热物体。本生灯不使用时绝不要停留在黄色安全火焰上；仅在加热时调至蓝色火焰，用后立即关闭。

Report any breakage of glassware immediately. Do not touch broken glass with bare hands; use a dustpan and brush. Check electrical circuits before turning on the power, and never handle bare wires with wet hands.

如有玻璃器皿破损，立即报告。切勿徒手触碰碎玻璃，应使用簸箕和刷子。接通电路前先检查，绝不用湿手触碰裸露导线。

2. Accurate Measurement of Length | 长度的精确测量

For simple lengths, use a metre rule or half-metre rule. Ensure you position your eye directly above the mark to avoid parallax error. The smallest division on a typical metre rule is 1 mm, so readings can be taken to the nearest 0.5 mm.

简单长度用米尺或半米尺测量。确保眼睛正对刻度线上方，以避免视差。普通米尺的最小刻度是1 mm，因此读数可估读到0.5 mm。

For greater precision, use vernier calipers (resolution 0.1 mm or 0.05 mm) or a micrometer screw gauge (resolution 0.01 mm). With vernier calipers, read the main scale against the zero mark of the vernier, then find which vernier division aligns with a main scale division and add the corresponding fraction.

需要更高精度时，使用游标卡尺（分辨率为0.1 mm或0.05 mm）或螺旋测微器（分辨率0.01 mm）。使用游标卡尺时，先读主尺上位于游标零刻线左侧的整数值，再找与主尺刻度对齐的游标刻度线，并将对应的小数值加上。

When using a micrometer screw gauge, check for zero error before taking any measurement. Close the gap gently using the ratchet and note whether the zero line aligns. A positive zero error must be subtracted, and a negative zero error must be added to the final reading.

使用螺旋测微器时，测量前必须先检查零误差。用棘轮轻轻闭合测量面，观察零线是否对齐。正零误差需从最终读数中减去，负零误差则需加上。

3. Measuring Time and Reducing Reaction Error | 时间测量与减小反应误差

Digital stopwatches give readings to 0.01 s, but human reaction time is typically about 0.2 s. To reduce the effect of reaction time, always measure time for multiple oscillations (e.g. 20 swings of a pendulum) rather than a single event.

数字秒表读数可到0.01 s，但人的反应时间通常在0.2 s左右。为了减小反应时间的影响，应测量多次重复事件的总时间（例如单摆摆动20次），而不是单次事件。

Start the stopwatch at a well-defined point, such as the centre of oscillation where speed is maximum, and count from zero. Press the start and stop buttons smoothly and consistently. Repeat the timing measurement at least three times to calculate an average period.

在清晰的参考点开始计时，例如摆动中心（速度最大处），并从零开始计数。平稳一致地按下启动和停止按钮。至少重复计时测量三次，然后计算平均周期。

For timing a cooling curve or motion down a ramp, ensure the stopwatch is started at the exact instant the event begins. Two people can help: one releases the object while the other starts the timer when the release is observed.

在测量冷却曲线或物体沿斜面下滑的时间时，确保秒表在事件开始的精确瞬间启动。双人配合很有帮助：一人释放物体，另一人观察到释放动作时启动秒表。

4. Mass, Volume and Density Determination | 质量、体积与密度的测定

Measure mass with a digital balance or a beam balance. Always check that the balance indicates zero before placing any object. Record the mass to the nearest 0.1 g or 0.01 g depending on the balance's resolution.

用电子天平或梁式天平测量质量。放置物体前，务必检查天平是否归零。根据天平的分辨率，记录质量至0.1 g或0.01 g。

Regular solid volumes can be calculated from length measurements. For irregular solids, use a displacement method: partly fill a measuring cylinder with water, note the initial volume, immerse the solid without splashing, and note the final volume. The volume of the solid is the difference.

规则固体的体积可由长度测量值计算得出。不规则固体用排水法测量：量筒中装入适量水，记录初始体积，将固体完全浸没且无溅出，记录末体积。固体体积等于两者之差。

ed; check the correct level. Density is calculated as ρ = m / V, with units typical of g/cm³ for solids and g/cm³ or kg/m³ for liquids.

读取量筒时，视线与凹液面底部齐平。对于水以外的液体（如水银），液面可能凸起，需确定正确读数位置。密度通过 ρ = m / V 计算，固体常用单位 g/cm³，液体可用 g/cm³ 或 kg/m³。

5. Recording Data and Significant Figures | 数据记录与有效数字

All raw data must be recorded directly into a prepared table with clear headings, units (e.g. Length / cm) and consistent decimal places. Do not write data on scraps of paper; examiners expect to see neat, organised tables in the report.

所有原始数据必须直接记录在事先准备好的表格中，表头清晰、包含单位（如 Length / cm），且小数位数保持一致。不要在废纸上记录数据；考官期望在报告中看到整洁有序的表格。

The number of significant figures in a measurement should reflect the precision of the instrument. For example, a metre rule reading of 15.2 cm has three significant figures, while 15.25 cm from a vernier caliper has four. Do not over-state precision by adding extra zeros or digits beyond what the instrument can deliver.

测量值的有效数字位数应反映仪器的精确度。例如，米尺读出的15.2 cm有三位有效数字，游标卡尺读出的15.25 cm有四位有效数字。不要超出仪器能力多写零或数字，以免夸大精度。

When computing averages, keep one more significant figure during calculation than the raw data, then round the final result appropriately. Record the mean with the same precision as the individual measurements.

计算平均值时，运算过程中可多保留一位有效数字，最后再将结果适当修约。记录的平均值应与各单次测量值的精度保持一致。

6. Constructing Graphs the Right Way | 正确绘制图表

Choose a suitable scale so that the data points fill at least half of the graph paper in both directions. Use simple multiples such as 1, 2, 5 or 10 units per large square. Avoid awkward scales like 3 or 7 per square.

选择合适的比例，使数据点在图纸的两个方向上都至少占据一半纸面。采用每大格1、2、5或10个单位这样的简单倍数。避免使用每格3或7个单位这样的别扭比例。

Label each axis with the quantity and unit, e.g. 'Time / s' on the horizontal axis and 'Temperature / °C' int with a small, neat cross (×) or a dot with a circle around it. Do not use large blobs.

每个坐标轴都要标注物理量和单位，例如横轴为 'Time / s'，纵轴为 'Temperature / °C'。用细小整齐的叉号（×）或带圆圈的圆点标出数据点。不要画成大的墨团。

After plotting, draw the best-fit straight line or smooth curve. The line should have an even balance of points on either side. If a point lies far from the trend, circle it and treat it as an anomaly; do not force the line to pass through it or through the origin unless there is a good physical reason.

描点后，画出最佳拟合直线或光滑曲线。这条线应使两侧数据点均匀分布。如果某点远离趋势，将其圈出视为异常点；不要强行使直线穿过该点或坐标原点，除非有明确的物理理由。

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7. Analysing Graphs: Slope and Intercepts | 分析图表：斜率与截距

dient = Δy / Δx. Always show the triangle on the graph and state the unit of the gradient.

对于直线图，选取直线上两个间距较大的点（非原始数据点）计算斜率。使用公式：斜率 = Δy / Δx。务必在图上画出斜边三角形，并写明斜率的单位。

ine beyond the plotted points to read the intercept, use a dashed line. Interpret the meaning of the intercept in the context of the experiment.

纵轴截距给出了 x = 0 时 y 的值。如果需要将线延长至数据点之外来读取截距，应使用虚线。结合实验背景解释截距的物理意义。

When checking proportionality, the line must be straight and pass through the origin. If it is straight but does not pass through the origin, the relationship is linear but not directly proportional.

判断正比关系时，图线必须是直线且穿过原点。如果图线是直线但不通过原点，该关系为线性关系，而非正比关系。

8. Understanding Uncertainty and Error | 理解不确定度与误差

Random errors cause readings to be scattered around the true value. They can be reduced by taking several measurements and calculating the mean, and by using instruments with better resolution.

随机误差导致读数分散在真值附近。可通过多次测量取平均值以及使用分辨率更高的仪器来减小随机误差。

Systematic errors cause all readings to be shifted in one direction. Examples include a balance that reads too high or a zero error on vernier calipers. They cannot be reduced by averaging; instead, the instrument must be recalibrated or the zero error corrected.

系统误差使所有读数向同一方向偏移，例如天平示值偏高，或游标卡尺存在零误差。系统误差不能通过取平均来减小，而应重新校准仪器或修正零误差。

surement with a stopwatch, the uncertainty is dominated by human reaction time, often quoted as ±0.2 s.

单次测量的绝对不确定度通常取最小刻度的一半（例如米尺为 ±0.5 mm）。使用秒表测量时间时，不确定度主要由人的反应时间决定，常取 ±0.2 s。

When combining measurements for derived quantities, percentage uncertainties should be added. For example, if length uncertainty is 2% and width uncertainty is 1%, the area uncertainty is about 3%. This is an important skill for evaluating the reliability of a result.

当测量值组合为导出量时，应将百分比不确定度相加。例如，长度的不确定度为2%，宽度的不确定度为1%，那么面积的不确定度约为3%。这是评估结果可靠性的重要技能。

9. Common Practicals: Oscillation, Circuits, Thermal | 常见实验：振动、电路、热学

Pendulum experiment: Measure the period T for different lengths L and plot T² against L. The gradient of the line gives 4π²/g, from which the acceleration of free fall g can be calculated. Keep the amplitude small (less than 10°) to ensure the motion is approximately simple harmonic.

单摆实验：测量不同摆长 L 的周期 T，绘制 T² 对 L 的图像。图线的斜率等于 4π²/g，由此可计算自由落体加速度 g。振幅保持小角度（小于10°），以确保运动近似为简谐运动。

Resistance of a wire: Set up a circuit with a power supply, ammeter in series, voltmeter in parallel across the wire, and a variable resistor or rheostat to vary the current. Measure the current I and potential difference V for different lengths of constantan wire. Plot V against I, and determine resistance R from the gradient. Keep the current low to avoid heating the wire, which changes resistance.

金属丝电阻实验：搭建电路，包含电源、串联的电流表、并联在电阻丝两端的电压表，以及用来调节电流的变阻器。测量不同长度康铜丝的电流 I 和电势差 V。绘制 V–I 图，从斜率得出电阻 R。保持电流较小以避免导线发热，否则电阻会改变。

Cooling curve: Heat a substance (e.g. stearic acid or water) in a boiling tube well above its melting point or boiling point, then allow it to cool. Record the temperature at regular time intervals (e.g. every 30 seconds) while stirring gently. Plot temperature versus time. A plateau in the graph indicates a change of state at constant temperature.

冷却曲线：将物质（如硬脂酸或水）在沸水浴中加热至远高于其熔点或沸点，然后让其自然冷却。每隔固定时间（如30秒）记录温度，同时轻轻搅拌。绘制温度-时间图。图像上的平台表明在恒定温度下发生了物态变化。

Investigating reflection and refraction: Use a ray box, a plane mirror, and a rectangular glass block. For reflection, mark incident and reflected rays and measure angles against the normal. Verify that the angle of incidence equals the angle of reflection. For refraction, observe the bending of light as it passes from air to glass and back to air. Draw ray diagrams and measure the angles of incidence and refraction.

探究反射与折射：使用光线盒、平面镜和矩形玻璃块。对于反射，标记入射光线和反射光线，测量与法线的夹角，验证入射角等于反射角。对于折射，观察光线从空气进入玻璃、再从玻璃进入空气时的偏折。绘制光路图，测量入射角和折射角。

10. Evaluating the Experiment and Improvements | 评估实验与改进

After obtaining results, always comment on their reliability. State the largest source of error and suggest a realistic improvement. For example, in the pendulum experiment, using a fiducial marker and a longer total counting time reduces reaction error.

获得结果后，务必评价其可靠性。指出最大的误差来源，并提出可行的改进建议。例如，在单摆实验中，使用参考标记并延长总计时间，可减少反应误差。

peated to confirm. Comparison with accepted values (e.g. standard value of g = 9.81 m/s²) allows calculation of percentage error: % error = |(experimental – accepted)| / accepted × 100%.

如果图上有异常点，应指出可能的原因，如刻度误读或外部干扰，并说明需要重复实验以确认。与公认值（例如标准重力加速度值 g = 9.81 m/s²）比较，可计算百分误差：百分误差 = |(实验值 – 公认值)| / 公认值 × 100%.

Finally, evaluate whether the collected data range is sufficient. If only three lengths were tested, suggest taking measurements at six or more lengths so the gradient of the graph is more reliable. Always propose a specific, practical improvement rather than a vague statement.

最后，评估所收集数据的范围是否充分。如果只测试了三个长度，建议至少测量六个或更多长度，使图像斜率更可靠。始终提出具体、可行的改进措施，而非含糊的陈述。

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