📚 Year 12 WJEC Physics: Experiment/ Practical Assessment Key Points | Year 12 WJEC 物理：实验/实践考核要点
Mastering the practical component is central to success in Year 12 WJEC Physics. While you may carry out experiments in class, your understanding of experimental design, data analysis and evaluation is rigorously tested in the written papers for Unit 1 (Motion, Energy and Matter) and Unit 2 (Electricity and Waves). This guide covers the essential practical skills, common pitfalls and the prescribed practical tasks you need to revise to perform confidently in your AS examinations.
掌握实验内容是 Year 12 WJEC 物理取得好成绩的关键。尽管实验操作在课堂中进行，但你对实验设计、数据分析和评估的理解将在单元一（运动、能量和物质）与单元二（电和波）的笔试中被严格考查。本指南总结了必备的实践技能、常见误区以及你需要复习的指定实验任务，帮助你在 AS 考试中自信发挥。
1. Understanding Practical Assessment Objectives | 理解实践考核目标
WJEC AS Physics places around 15% of marks on practical skills, assessed through questions linked to the specified practical work. These questions evaluate your ability to apply investigative approaches, interpret experimental data and critically evaluate procedures.
WJEC AS 物理约 15% 的分值考查实践技能，题目围绕指定的实验工作展开。这些问题会评估你运用研究方法、解释实验数据以及批判性评价实验步骤的能力。
Assessment Objective 2 (AO2) requires you to apply knowledge and understanding of scientific ideas and techniques in a practical context. AO3 demands that you analyse, interpret and evaluate scientific information, making reasoned judgments and reaching conclusions.
评估目标二（AO2）要求你在实践情境中运用科学思想与技术的知识和理解。评估目标三（AO3）则要求你分析、解释和评价科学信息，做出合理判断并得出结论。
You will need to demonstrate competencies such as correctly identifying variables, selecting appropriate measuring instruments, calculating uncertainties and suggesting valid improvements. Familiarity with the mark schemes for practical-based questions is essential.
你需要展示的能力包括：正确识别变量、选择合适的测量仪器、计算不确定度以及提出有效的改进建议。熟悉实践类问题的评分方案至关重要。
2. Planning and Experimental Design | 实验规划与设计
A clear plan begins by identifying the independent, dependent and control variables. For instance, when investigating the period of a pendulum, the length is the independent variable, the period T is the dependent variable, and the mass of the bob and angle of release must be kept constant.
清晰的实验规划从识别自变量、因变量和控制变量开始。例如，研究单摆周期时，摆长是自变量，周期 T 是因变量，而摆锤质量和释放角度必须保持不变。
Choose apparatus that gives the required precision without introducing unnecessary systematic error. For length measurements, a metre rule is fine for large distances, but a micrometer screw gauge should be used for the diameter of a wire to determine the Young modulus.
选择能提供所需精度的仪器，同时避免引入不必要的系统误差。测量长度时，米尺适用于较大距离，但测定杨氏模量时导线的直径应使用千分尺测量。
Your plan should include a step-by-step method that is easy to replicate, along with any safety precautions, such as using a low-voltage power supply for electrical circuits or wearing goggles when stretching wires.
实验计划应包含易于重复的分步操作方法，以及所有安全预防措施，例如电路中使用低压电源或在拉伸导线时佩戴护目镜。
3. Measurements and Instrumentation | 测量与仪器使用
d always record the resolution. A digital voltmeter showing 1.23 V has a resolution of 0.01 V, giving an absolute uncertainty of ±0.005 V if only one reading is taken.
准确的测量是可靠数据的基础。尽可能将仪器读数读取到最小分度值的一半，并始终记录分辨率。显示 1.23 V 的数字电压表分辨率为 0.01 V，如果只取一次读数，绝对不确定度为 ±0.005 V。
Use vernier callipers and micrometers correctly, checking for zero errors before starting. For repeated measurements of a quantity, such as the time for 20 oscillations of a pendulum, calculate the mean and use the half-range (largest value – smallest value)/2 as an estimate of the random uncertainty.
正确使用游标卡尺和千分尺，使用前检查零误差。对于重複测量，例如测量单摆 20 次摆动的时间，计算平均值并使用半极差（最大值 – 最小值）/2 作为随机不确定度的估计值。
When using electrical meters, ensure they are on the correct range to give a sensible deflection. For analogue meters, avoid parallax error by viewing the scale perpendicularly.
使用电表时，确保量程合适以获得合理的偏转。使用模拟表时，垂直观察刻度以避免视差。
4. Handling Uncertainties and Errors | 处理不确定度与误差
Distinguish between systematic errors (which affect accuracy) and random errors (which affect precision). A poorly zeroed balance introduces systematic error, whereas human reaction time in starting a stopwatch causes random scatter.
区分系统误差（影响准确度）和随机误差（影响精确度）。未调零的天平会引入系统误差，而按停秒表时的反应时间则导致随机散布。
alf-range. Combine uncertainties when quantities are added or subtracted by adding absolute uncertainties: if x = a + b, then Δx = Δa + Δb.
对于单次读数，绝对不确定度通常取最小分度值的一半。对于同一量的多次读数，使用半极差。当量相加或相减时，组合不确定度为绝对不确定度之和：若 x = a + b，则 Δx = Δa + Δb。
r quantities multiplied or divided, percentage uncertainties are added. If R = V / I, then %R = %V + % ived quantities with the correct absolute uncertainty and appropriate significant figures.
对于相乘或相除的量，百分不确定度相加。若 R = V / I，则 %R = %V + %I。始终用正确的绝对不确定度和合适的有效数字表达导出量。
5. Recording and Presenting Data | 数据记录与呈现
Design results tables before starting the experiment. Each column heading must include the quantity and its unit in the format: Length l / cm. Record raw data to the full precision of the instrument, including trailing zeros where necessary.
实验开始前先设计结果表格。每个列标题必须包含量和单位，格式如：长度 l / cm。以仪器的完整精度记录原始数据，必要时应保留末尾的零。
When recording repeated readings, do not discard values unless there is a clear anomalous result identified by a large deviation. An anomaly should be circled on the table but not used in the calculation of the mean.
记录重复读数时，除非有明显的异常值（偏差很大），否则不要随意舍去数据。异常值应在表格中圈出，但不用于计算平均值。
Processed data, such as calculated means, squares or logarithms, should be placed in additional columns. Ensure that the number of significant figures in a calculated value reflects the precision of the input data.
处理后的数据，如计算出的平均值、平方值或对数值，应放在额外的列中。确保计算值有效数字的位数反映输入数据的精确度。
6. Graph Plotting and Analysis | 绘图与数据分析
e intervals, e.g., T / s and l / cm. Plot points using small crosses (×) or a dot in a circle.
绘制图表时，坐标轴的刻度应尽可能大，使两个方向均利用超过一半的网格区域。用物理量、单位和合适的间隔标注每个轴，如 T / s 和 l / cm。用小的叉号（×）或圆圈加点标记数据点。
Draw a best-fit straight line or smooth curve, balancing points on either side. Do not force the line through the origin unless the theory strictly demands it. Identify any outliers and exclude them from the line drawing decision.
画一条最佳拟合直线或平滑曲线，使两侧点的数量平衡。除非理论严格要求，否则不要强行让线通过原点。识别任何异常值，且不让它们影响线的走向。
ge triangle. Display the calculation clearly: gradient = (y₂ − y₁) / (x₂ − x₁) with units.
计算斜率时，在直线上选取相距较远的两个点（非原始数据点），并使用大的三角形。清晰展示计算过程：斜率 = (y₂ − y₁) / (x₂ − x₁) 并附上单位。
7. Linearising Equations and Gradients | 线性化方程与斜率
r intercept gives the target quantity. For example, the period of a simple pendulum T = 2π √l/g is squared to give T² = (4π²/g) l.
许多 WJEC 实验依赖将物理方程整理成 y = m x + c 的形式，这样斜率或截距便能给出目标物理量。例如，单摆的周期 T = 2π √l/g 通过平方得到 T² = (4π²/g) l。
A graph of T² against l should produce a straight line through the origin, and the gradient equals 4π²/g. By measuring the gradient, you can calculate g and compare with the accepted value of 9.81 m s⁻².
绘制 T² 对 l 的图，应得到一条过原点的直线，且斜率等于 4π²/g。通过测量斜率可计算出 g，并与公认值 9.81 m s⁻² 比较。
ivity ρ = R A / L, plotting R against L gives a straight line whose gradient equals ρ / A.
其他常见的线性化例子包括：杨氏模量 E = F L / (A e)，绘制应力对应变图，斜率给出 E；电阻率 ρ = R A / L，绘制 R 对 L 的图得到一条直线，其斜率等于 ρ / A。
8. Evaluation and Improvements | 评估与改进
After analysing data, discuss the main sources of uncertainty and their likely impact. For example, in a free-fall experiment to determine g, air resistance and the delay in the electromagnetic release are systematic errors that reduce the measured acceleration.
在分析数据之后，要讨论主要的误差来源及其可能的影响。例如，在测定 g 的自由落体实验中，空气阻力和电磁铁释放的延迟是系统误差，会使测得的加速度偏小。
Propose specific, practical improvements, such as using a taller drop to reduce the percentage uncertainty in timing, or replacing a stopwatch with light gates connected to a data logger for greater precision.
要提出具体、可行的改进措施，如使用更高的下落距离以减少计时的百分不确定度，或将秒表替换为连接数据记录器的光门以获得更高精度。
Compare your result with the standard value using a percentage difference: % difference = |experimental value – accepted value| / accepted value × 100% thin the range suggested by your uncertainty and whether the result is therefore reliable.
将你的结果与标准值比较，计算百分差异：百分差异 = |实验值 – 公认值| / 公认值 × 100%。讨论这一差异是否落在你的不确定度所建议的范围内，并由此判断结果是否可靠。
9. Common Core Practical Skills | 常见核心实践技能
In electrical experiments, always begin with the circuit connected but switched off, and use a variable resistor or potential divider to control current. When measuring resistance, wait for the wire to cool between readings to avoid thermal drift.
在电学实验中，务必先连接电路但保持开关断开，并使用变阻器或分压器控制电流。测量电阻时，两次读数之间等待导线冷却以避免热漂移。
For mechanics experiments, minimise friction by using air tracks or lubricated pulleys. When releasing a trolley down a ramp, ensure the initial velocity is zero and use a motion sensor to record displacement–time data.
对于力学实验，使用气垫导轨或润滑的滑轮以减小摩擦。当让小车沿斜面下滑时，确保初速度为零，并使用运动传感器记录位移 – 时间数据。
When handling oscilloscopes or signal generators for wave measurements, adjust the time base and voltage sensitivity to obtain a clear trace. Always measure peak-to-peak distances and use the scale correctly to find the period and amplitude.
使用示波器或信号发生器进行波动测量时，调节时基和电压灵敏度以获得清晰波形。始终测量峰峰值距离并正确使用刻度来确定周期和振幅。
10. Key Practicals for Year 12 WJEC | Year 12 WJEC 重点实验
len are recorded. Plotting 2h against t² gives a gradient equal to g, analysed from the kinematic equation h = ½ g t².
自由落体法测定 g：钢球从电磁铁释放，下落通过两个光门，记录时间间隔和下落距离。由运动学方程 h = ½ g t²，绘制 2h 对 t² 的图，其斜率等于 g。
Investigation of Hooke' ile its extension is measured. The Young modulus is obtained from the gradient of a stress–strain graph, with stress = F/A and strain = e/L.
研究胡克定律和杨氏模量：分步对导线加载并测量其伸长量。杨氏模量由应力 – 应变图的斜率得出，其中应力 = F/A，应变 = e/L。
The resistance R of constantan wire is measured for different lengths L using a voltmeter– the resistivity ρ to be found via ρ = (gradient) × A, where A is the cross-sectional area.
金属导线电阻率测量：用伏安法测量康铜导线不同长度 L 对应的电阻 R。绘制 R 对 L 的图，通过 ρ = (斜率) × A 可求得电阻率，其中 A 是横截面积。
on. The speed v is calculated from v = f λ, with λ = 4(L + 0.3d) for a tube with one closed end.
利用共振管测定声速：将音叉置于管口，改变管长找到第一共振位置。对于一端封闭的管子，λ = 4(L + 0.3d)，声速 v = f λ。
Young' ring the fringe spacing w, the slit separation s and the distance D allows λ to be found from λ = w s / D.
杨氏双缝实验测波长：单色光通过双缝，在屏幕上形成干涉条纹。测量条纹间距 w、双缝间距 s 和双缝到屏幕的距离 D，由 λ = w s / D 计算波长。
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