📚 Year 7 CIE Physics: Key Points for Practical Exams | Year 7 CIE 物理：实验/实践考核要点
Practical assessments are an essential part of Year 7 CIE Physics. They test your ability to design experiments, take accurate measurements, analyse data and draw valid conclusions. This guide highlights the key experimental skills and exam tips you need to master.
实验评估是 Year 7 CIE 物理的重要组成部分。它考察你设计实验、准确测量、分析数据和得出有效结论的能力。本指南重点介绍了你需要掌握的关键实验技能和考试技巧。
1. Understanding Key Variables | 理解关键变量
In every experiment, you must identify the independent variable (the one you change), the dependent variable (the one you measure), and the control variables (those kept constant). For example, when investigating how the extension of a spring depends on the force applied, the force is the independent variable, the extension is the dependent variable, and the type of spring, its original length and room temperature are control variables.
在每个实验中，你必须识别出独立变量（你改变的变量）、因变量（你测量的变量）和控制变量（保持不变的变量）。例如，在研究弹簧的伸长量如何随施加的力变化时，力是独立变量，伸长量是因变量，而弹簧的种类、原长和室温是控制变量。
A fair test is achieved when only the independent variable is changed, and all other factors are kept the same. This ensures that any observed effect is caused by the independent variable alone.
只有独立变量变化、其他因素保持不变时，才能实现公平测试。这确保了观察到的任何效应都是由独立变量单独引起的。
2. Accurate Measurement and Instruments | 精确测量与仪器
Using the correct instruments and reading them accurately is crucial. Common physics instruments in Year 7 include metre rulers, stopwatches, forcemeters (spring balances), ammeters and voltmeters. Always read the scale at eye level to avoid parallax error. Repeat readings and take the average to improve reliability.
使用正确的仪器并准确读取数值至关重要。Year 7 常见的物理仪器包括米尺、秒表、测力计（弹簧秤）、电流表和电压表。读数时眼睛要与刻度平齐，以避免视差误差。重复读数并取平均值可以提高可靠性。
| Instrument | Quantity Measured | Typical Unit |
|---|---|---|
| Metre ruler | Length | mm, cm, m |
| Stopwatch | Time | s |
| Forcemeter | Force | N |
| Ammeter | Current | A |
| Voltmeter | Voltage | V |
以上仪器分别测量长度（米尺，单位 mm, cm, m）、时间（秒表，单位 s）、力（测力计，单位 N）、电流（电流表，单位 A）和电压（电压表，单位 V）。使用前检查零误差，确保所有仪器都校准归零。
3. Recording Data in Tables | 用表格记录数据
Always record data in organised tables with clear headings that include units, such as Force (N) and Extension (cm). Take at least three repeated readings for each measurement, calculate the mean, and record it in a separate column. This reduces random errors.
始终将数据记录在清晰的表格中，表头要包含单位，如 Force (N) 和 Extension (cm)。每个测量值至少取三次重复读数，计算平均值并记录在单独的一列中，从而减小随机误差。
Record readings with the correct number of decimal places, matching the precision of the instrument. For instance, a standard metre ruler reads to the nearest 1 mm (0.1 cm), so all length readings should be written to one decimal place in cm.
根据仪器的精确度记录读数时要保留正确的小数位数。例如，标准米尺能读到最近的 1 毫米（0.1 厘米），因此所有长度读数用厘米表示时应保留一位小数。
If a table of results is provided in the exam, check the column headings for units and the values for any obvious outliers before plotting a graph.
如果考试中给出了结果表格，在画图之前要检查列标题的单位和数值中是否有明显的异常值。
4. Plotting and Interpreting Graphs | 绘制与解读图表
Plot the independent variable on the x‑axis (horizontal) and the dependent variable on the y‑axis (vertical). Label both axes with the quantity and unit, e.g. 'Force (N)' and 'Extension (cm)' ale that uses more than half of the graph paper and is easy to read, such as 1 cm = 0.1 N.
将独立变量画在 x 轴（横轴），因变量画在 y 轴（纵轴）。两个轴都标出物理量和单位，比如 'Force (N)' 和 'Extension (cm)'。选择的标度应占据图纸的一半以上且容易读取，例如 1 厘米 = 0.1 N。
Draw a sharp pencil 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. For a spring extension graph, a straight line passing through the origin shows direct proportionality and obeys Hooke’s law.
用削尖的铅笔绘制一条最佳拟合线——一条尽可能多的点通过、两侧点数大致相等的直线或平滑曲线。对于弹簧伸长量图，一条通过原点的直线表明两个变量成正比，遵循胡克定律。
F = k × x
The gradient of the line equals the spring constant, k. Calculate the gradient by choosing two points far apart on the line, not from the data table.
直线的斜率等于弹簧常数 k。计算斜率时应选取直线上相距较远的两个点，而不是取自数据表。
5. Analyzing Data and Drawing Conclusions | 分析数据并得出结论
Examine the table and graph for patterns. If doubling the independent variable doubles the dependent variable, the variables are directly proportional. Use the graph to make predictions – for example, finding the force for a given extension by reading from the line of best fit.
仔细检查表格和图表中的规律。如果独立变量加倍时因变量也加倍，那么这两个变量成正比。利用图表进行预测——例如，通过从最佳拟合线上读取给定伸长量对应的力。
A strong conclusion must refer directly to the data. Instead of writing 'The spring stretched more when we added more weight', say 'The extension increased in proportion to the force; for every 1 N added, the spring extended by 2 cm.'
严谨的结论必须直接引用数据。不要写“加更多重量时弹簧伸得更长”，而应写“伸长量与力成正比；每增加 1 N 的力，弹簧伸长 2 cm。”
Always state whether your results support the original prediction and name any scientific law where relevant, such as Hooke’s law or Ohm’s law for a fixed resistor.
始终说明结果是否支持最初的预测，并在相关时指出科学定律，例如胡克定律或定值电阻的欧姆定律。
6. Identifying Sources of Error and Improvements | 识别误差来源与改进
Random errors occur due to unpredictable factors such as slight differences in reaction time when using a stopwatch. They can be reduced by taking several readings and calculating the average. Systematic errors, like a zero error on a forcemeter, affect all readings equally; always check the zero point before each use and subtract the zero reading if necessary.
随机误差由不可预测的因素引起，如使用秒表时反应时间的微小差异。通过多次读数并计算平均值可以减小随机误差。系统误差（如测力计的零误差）对所有读数的影响相同；每次使用前务检查零点，必要时减去零读数。
Parallax error is a common mistake when reading an analogue scale at an angle. Always read the scale with your eye exactly in line with the marking. You can also suggest using digital instruments or instruments with finer scales (e.g. a vernier caliper instead of a metre ruler) for more precise measurements.
视差误差是斜视模拟刻度时的常见错误。一定要将眼睛与刻度标记完全对齐来读数。你也可以建议使用数字仪器或分度值更小的仪器（如用游标卡尺代替米尺）来获得更精确的测量。
In an evaluation, always link improvements to specific errors. For example, 'The experiment can be improved by clamping the ruler vertically and using a set square to measure the extension accurately, reducing parallax error.'
在评估中，务必把改进建议与具体误差联系起来。例如，“可以用夹子将尺子垂直固定，并用三角尺准确测量伸长量，从而减小视差误差。”
7. Safety Precautions in Physics Lab | 物理实验室的安全预防措施
Wear safety goggles whenever you work with stretched springs, moving objects, or electrical circuits that may overheat. Tie back long hair and secure any loose clothing or jewellery. Stand up during practical work so you can move away quickly if something goes wrong.
在处理拉伸弹簧、运动物体或可能过热的电路时，要始终佩戴安全护目镜。将长发扎起，束好宽松的衣服和饰品。实验过程中保持站立，以便发生意外时能迅速移开。
When building circuits, always switch off the power supply before making or changing connections. Never touch bare wires or components with wet hands, and avoid short circuits by checking that the circuit is arranged correctly before switching on.
搭建电路时，在连接或更改接线前务必关闭电源。切勿用湿手触摸裸露导线或元件；开启电源前检查电路连接正确，避免短路。
If heating is involved (e.g., investigating thermal expansion), use a heat‑proof mat and never leave a Bunsen burner unattended. Always point the open end of a boiling tube away from yourself and others.
如果有加热操作（例如研究热膨胀），要使用隔热垫，且绝不能让本生灯无人看管。沸腾管开口端始终要朝向无人的方向。
8. Common Year 7 Physics Experiments | 常见 Year 7 物理实验
Experiment A: Measuring speed. peed = distance ÷ time. Repeat trials and average the times to make the result more reliable.
实验A：测量速度。 让玩具小车从斜面滑下。用米尺测量行驶距离，用秒表测量时间。利用公式计算平均速度：速度 = 距离 ÷ 时间。重复实验并对时间取平均值，提高结果的可靠性。
Experiment B: Stretching a spring. asses one by one, and record the new length each time. Calculate the extension (new length – × 10 N/kg) against extension. A straight line through the origin demonstrates Hooke’s law.
实验B：弹簧拉伸。 将弹簧悬挂在铁架台上，测量其原长。逐个增加槽码，每次记录新的长度。计算伸长量（新长度 − 原长）。绘制力（重量 = 质量 × 10 N/kg）与伸长量的关系图。通过原点的直线表明遵循胡克定律。
Experiment C: Simple circuits. Build a series circuit containing a cell, a bulb, and an ammeter. Add a voltmeter in parallel across the bulb. Record the current and voltage for different numbers of cells. Describe how the bulb's brightness changes and relate it to the current.
实验C：简单电路。 搭建包含一个电池、一个灯泡和一个电流表的串联电路。在灯泡两端并联一个电压表。记录不同数量电池时的电流和电压。描述灯泡亮度如何变化，并将其与电流联系起来。
Experiment D: Density of solids. e mass, then lower it into a measuring cylinder partly filled with water; the rise in water level gives the volume. Density = mass ÷ volume.
实验D：固体的密度。 对于规则长方体，用电子天平测量质量，通过长×宽×高计算体积。对于不规则石块，先测质量，然后将其放入盛有部分水的量筒中，水位上升的高度差即为体积。密度 = 质量 ÷ 体积。
Experiment E: Magnetic forces. Attach a forcemeter to a paperclip held against a magnet. Pull until the paperclip just detaches, and record the force. Change the number of magnets or the separation distance and observe how the force changes. This shows how magnetic force depends on distance and strength. Published by TutorHao | Year 7 Physics Revision Series | aleveler.com
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