📚 IGCSE Edexcel Physics: Practical Investigation Guide | IGCSE Edexcel 物理：实验操作指南
Mastering practical investigations is essential for IGCSE Edexcel Physics, as it accounts for a significant portion of your final grade and deepens your understanding of physical concepts. This guide walks you through key laboratory skills, core required practicals, data handling, and error analysis to help you excel in both coursework and written examinations.
掌握实验操作对于IGCSE Edexcel 物理至关重要，它不仅占最终成绩的很大比重，还能加深你对物理概念的理解。本指南将带你浏览关键的实验室技能、核心必做实验、数据处理和误差分析，帮助你在课程作业与笔试中取得优异成绩。
1. Lab Safety and Preparation | 实验安全与准备工作
Before starting any experiment, always wear safety goggles and a lab coat to protect yourself from potential hazards. Tie back long hair and avoid loose clothing that could catch fire or get caught in equipment.
在开始任何实验之前，务必佩戴护目镜和实验服以保护自己免受潜在危害。将长发束起，避免穿着可能着火的宽松衣物或被设备卷入的衣物。
Familiarise yourself with the location of safety equipment such as fire extinguishers, eye wash stations, and first aid kits. Read the procedure thoroughly and check that all apparatus is clean and in good working order before you begin.
熟悉安全设备的位置，如灭火器、洗眼器和急救箱。开始前仔细阅读步骤，并检查所有仪器是否清洁且运作正常。
- Always work in a well-ventilated area when dealing with fumes or heating.
- 进行有烟雾或加热的实验时，务必在通风良好的地方工作。
- Never taste or touch chemicals; use heat-proof mats when heating.
- 切勿品尝或触摸化学药品；加热时使用隔热垫。
- Turn off power supplies and gas taps immediately after use.
- 使用后立即关闭电源和煤气阀。
2. Measurements and Uncertainties | 测量与不确定度
All physical measurements have an inherent uncertainty. The uncertainty is usually taken as ± half of the smallest division on the measuring instrument, unless the instrument’s precision is specified otherwise. For a metre ruler with 1 mm divisions, the absolute uncertainty is ±0.5 mm.
所有物理测量都具有固有的不确定度。不确定度通常取测量仪器最小刻度的一半，除非仪器精度另有说明。对于刻度为1 mm的米尺，绝对不确定度为±0.5 mm。
When taking repeated readings, the uncertainty can be estimated by the spread of values. Record your readings to the correct number of decimal places, and always state uncertainties alongside your results to allow meaningful comparisons.
当进行重复读数时，不确定度可以通过数值的分布范围来估算。按正确的小数位数记录读数，并始终在结果旁注明不确定度，以便进行有意义的比较。
3. Experiment 1: Measuring Density | 实验一：测量密度
The density of a material is defined as mass per unit volume, given by the formula:
ρ = m ÷ V
材料的密度定义为单位体积的质量，公式如上。其中ρ代表密度，m代表质量，V代表体积。
To find the density of a regular solid, measure its mass using a digital balance. Determine the volume by measuring its dimensions with a ruler or vernier callipers and using the appropriate geometric formula (e.g. V = l × w × h for a cuboid).
要测量规则固体的密度，用电子天平测量其质量。用直尺或游标卡尺测量尺寸，并使用相应的几何公式计算体积（例如长方体 V = 长 × 宽 × 高）。
For an irregular solid, submerge it in a measuring cylinder partly filled with water and measure the rise in water level. The volume of the solid equals the displacement volume. For a liquid, measure the mass of an empty measuring cylinder, then fill it with the liquid, reweigh, and subtract to find the mass of the liquid. The volume is read directly from the cylinder.
对于不规则固体，将其浸入盛有部分水的量筒中，测量水位上升。固体的体积等于排开的水的体积。对于液体，先称量空量筒的质量，然后倒入液体，再次称重，相减得到液体质量。体积直接从量筒上读取。
Repeat measurements and use an average to reduce random errors. Always check for zero errors on the balance before weighing.
重复测量并使用平均值以减少随机误差。称重前务必检查天平是否有零位误差。
4. Experiment 2: Investigating Hooke’s Law | 实验二：研究胡克定律
Hooke’s law states that the extension of a spring is directly proportional to the load applied, provided the elastic limit is not exceeded:
F = k x
胡克定律指出，在不超过弹性限度的情况下，弹簧的伸长量与所施加的负载成正比，公式如上。F是力，k是弹簧常数，x是伸长量。
Suspend a spring from a clamp stand and attach a pointer and a ruler to read the extension accurately. Add masses one at a time, recording the new length each time. Extension = new length − original length. Plot a graph of force (weight = mg) against extension.
将弹簧悬挂在铁架台上，附上指针和直尺以准确读取伸长量。逐次添加砝码，每次记录新长度。伸长量 = 新长度 − 原长。绘制力（重力 = mg）与伸长量的关系图。
The graph should be a straight line through the origin, and the gradient gives the spring constant k. If the line begins to curve, you have exceeded the elastic limit. Ensure the spring is not swinging when you take readings.
图表应为一条过原点的直线，其斜率即为弹簧常数 k。如果曲线开始弯曲，说明已超出弹性极限。读数时要确保弹簧没有摆动。
5. Experiment 3: Measuring Average Speed of a Moving Object | 实验三：测量运动物体的平均速度
Average speed is found by dividing the total distance travelled by the time taken:
v = s ÷ t
平均速度通过总路程除以所用时间求得，公式如上。
A common practical involves a toy car or a trolley rolling down a ramp. Mark a start and finish line a known distance s apart. Use a stopwatch to measure the time t taken to travel this distance. For greater accuracy, use light gates connected to a data logger.
一个常见实验是小车或滑块沿斜面滑下。标记相距已知距离 s 的起点线和终点线。使用秒表测量通过这段距离所需的时间 t。为了更精确，可以使用连接数据采集器的光门。
Repeat several times and calculate mean time to minimise reaction time errors. The light gates eliminate human reaction time entirely, giving a more precise measurement. Values of v can be compared for different ramp heights.
重复多次并计算平均时间，以减小反应时间误差。光门完全消除了人为反应时间，提供更精确的测量结果。可以比较不同斜面高度下的 v 值。
6. Experiment 4: Investigating Reflection of Light | 实验四：研究光的反射
The law of reflection states that the angle of incidence i equals the angle of reflection r, and both are measured with respect to the normal line perpendicular to the surface.
反射定律指出，入射角 i 等于反射角 r，两者均相对于垂直于表面的法线测量。
Place a plane mirror on a sheet of white paper and draw its outline. Use a ray box to direct a single narrow beam of light towards the mirror at an angle. Mark the incident and reflected rays with pencil dots along the beam. Remove the mirror, draw the incident and reflected rays, and measure the angles using a protractor.
将平面镜放在一张白纸上，画出其轮廓。用光线盒发出一束窄光束以一定角度射向镜面。沿着光线用铅笔点标记入射光和反射光。移开镜子，画出入射和反射光线，用量角器测量角度。
Repeat for several angles of incidence and record results in a table. Check that i = r within experimental uncertainty. Avoid parallax error by viewing the protractor directly from above when measuring angles.
对多个人射角重复实验，并将结果记录在表格中。在实验不确定度范围内验证 i = r。测量角度时，从正上方观察量角器以避免视差误差。
7. Experiment 5: Investigating Refraction of Light | 实验五：研究光的折射
When light passes from one transparent medium to another, it changes direction. Snell’s law relates the angles:
n = sin i ÷ sin r
当光从一种透明介质进入另一种时，其方向会发生改变。斯涅尔定律关联了这些角度，公式如上，n为折射率。
Place a rectangular glass block on a sheet of paper and trace its outline. Direct a ray of light to enter one side at an angle of incidence i, and mark the emergent ray on the other side. Remove the block, join the points to show the refracted ray inside the block.
将矩形玻璃块放在一张纸上，描出其轮廓。使光线以入射角 i 射入一个侧面，并在另一侧标记出射光线。移开玻璃块，连接各点以显示块内折射光线。
Measure angles i and r with a protractor and calculate the refractive index n for each trial. Repeat for different values of i and find the mean of n. Compare your value with the known refractive index of glass (≈1.5).
用量角器测量角度 i 和 r，并计算每次实验的折射率 n。对不同的 i 值重复实验，并求出 n 的平均值。与你已知的玻璃折射率（约1.5）进行比较。
8. Experiment 6: Investigating Resistance of a Wire | 实验六：研究导线电阻
The resistance of a wire depends on its length, cross-sectional area, and resistivity of the material. Ohm’s law gives:
R = V ÷ I
导线的电阻取决于其长度、横截面积和材料的电阻率。欧姆定律公式如上。
Set up a circuit with a power supply, an ammeter in series, and a voltmeter in parallel across the test wire. Using crocodile clips, vary the length l of the wire under test. For each length, record the current I and voltage V, then calculate resistance R = V / I.
构建一个电路，包含电源、串联的电流表以及与被测导线并联的电压表。使用鳄鱼夹改变测试导线的长度 l。对每一长度，记录电流 I 和电压 V，然后计算电阻 R = V / I。
Plot a graph of R against l. The graph should be a straight line through the origin if temperature is constant. Keep the current low to avoid heating the wire, which would change its resistivity. Calculate the resistivity using R = ρl / A if the cross-sectional area A is known.
绘制 R 与 l 的关系图。如果温度恒定，图表应为一条过原点的直线。保持低电流以避免导线发热，因为这会使电阻率发生变化。如果已知横截面积 A，可用公式 R = ρl / A 计算电阻率。
9. Experiment 7: Investigating Series and Parallel Circuits | 实验七：研究串联和并联电路
In a series circuit, the total resistance is the sum of individual resistances: Rtotal = R₁ + R₂ + … . In a parallel circuit, the reciprocal of total resistance equals the sum of reciprocals: 1/Rtotal = 1/R₁ + 1/R₂ + … .
在串联电路中，总电阻为各电阻之和：R总 = R₁ + R₂ + …。在并联电路中，总电阻的倒数等于各电阻倒数之和：1/R总 = 1/R₁ + 1/R₂ + …。
Choose two identical resistors (e.g., 10 Ω each). First connect them in series: set up the circuit, measure V and I, and calculate total R. Then connect them in parallel, repeat the measurements, and find total R. Compare experimental results with theoretical values.
选择两个相同的电阻（例如各10 Ω）。首先将它们串联：连接电路，测量 V 和 I，计算总 R。然后将它们并联，重复测量并求出总 R。将实验结果与理论值进行比较。
Use the same battery voltage to ensure fair comparison. Ammeter connection is always in series; voltmeter in parallel with the resistor(s) being measured. Your values should show that the parallel combination gives a smaller resistance than either resistor alone.
使用相同电池电压以确保公平比较。电流表始终串联连接；电压表与被测电阻（组合）并联。实验值应显示并联组合的总电阻小于任一单个电阻。
10. Experiment 8: Measuring the Speed of Sound in Air | 实验八：测量空气中声音的速度
The speed of sound can be determined using the relationship between speed, frequency, and wavelength:
v = f λ
声音的速度可以利用速度、频率和波长之间的关系来测定，公式如上。
One method uses a tuning fork of known frequency f held over a resonance tube partly filled with water. Raise or lower the inner tube until the first loud resonance is heard. Measure the length of the air column L₁. Resonance occurs when the column length is ¼ of the wavelength for the fundamental tone, so λ = 4 L₁.
一种方法是使用已知频率 f 的音叉，将其置于部分装水的共振管上方。升高或降低内管，直到听到第一次响亮的共振。测量空气柱长度 L₁。基音共振发生在空气柱长度为波长的四分之一时，因此 λ = 4 L₁。
Calculate v using v = f × 4L₁. To improve accuracy, find the length L₂ for the second resonance (¾λ), then use λ = 2(L₂ − L₁). Repeat with different tuning forks and average your results. Avoid background noise and measure air temperature, as speed of sound increases with temperature.
使用 v = f × 4L₁ 计算声速。为提高精度，可找到第二次共振的长度 L₂（¾λ），然后利用 λ = 2(L₂ − L₁) 计算。用不同频率音叉重复实验并取平均值。避免背景噪音并测量空气温度，因为声速随温度升高而增加。
11. Recording Data and Drawing Graphs | 数据记录与图表绘制
All experimental data should be recorded clearly in a ruled table with headings that include the quantity and its unit, e.g., ‘Length l / m’ or ‘Voltage V / V’. The independent variable is placed in the left column, and the dependent variable(s) in the right columns.
所有实验数据都应清晰地记录在带表格线的表格中，表头包含物理量及其单位，例如 ‘长度 l / m’ 或 ‘电压 V / V’。自变量放在左列，因变量放在右列。
When plotting a graph, choose appropriate scales that utilise more than half the graph paper in each direction. Label axes with the quantity and unit, plot points with small crosses or dots with circles, and draw the best-fit straight line (or smooth curve) through the majority of points.
绘制图表时，选择能够使每个方向使用超过一半图纸的适当比例。在坐标轴上标出物理量和单位，用小十字或带圈的圆点标出数据点，并通过大多数点画出最适直线（或平滑曲线）。
If the line is straight and passes through the origin, it indicates direct proportionality between the variables. The gradient and intercept can provide further physical constants, such as the spring constant k or internal resistance r.
如果图线为直线且经过原点，则表明变量之间存在正比关系。斜率和截距可以给出进一步的物理常数，例如弹簧常数 k 或内阻 r。
12. Error Analysis and Improvements | 误差分析与改进
Random errors cause readings to be scattered around the true value. They can be reduced by taking multiple measurements and calculating the mean. Examples include human reaction time when using a stopwatch and slight fluctuations in the measuring instrument’s display.
随机误差导致读数围绕真值分散。可通过多次测量并计算平均值来减小。例子包括使用秒表时的人为反应时间以及测量仪器显示的轻微波动。
Systematic errors are consistent deviations from the true value, often caused by faulty equipment or poor experimental design, such as a zero error on an ammeter or a ruler that has a worn end. These cannot be reduced by averaging; instead, you must identify and correct the source, or apply a numerical correction.
系统误差是偏离真值的一致偏差，通常由设备故障或不良的实验设计引起，例如电流表的零位误差或尺子的磨损端。这些不能通过取平均值来减小；相反，你必须识别并纠正其来源，或进行数值修正。
Always evaluate your experiment by commenting on the accuracy of results and possible sources of error. Suggest practical improvements, such as using a digital meter instead of an analogue one, clamping the ruler vertically to avoid parallax, or using a temperature-controlled environment.
始终通过评论结果的准确性和可能的误差来源来评估你的实验。提出实际的改进建议，例如使用数字仪表代替模拟仪表、将直尺垂直固定以避免视差，或使用温控环境。
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