📚 Year 7 Cambridge Physics: Practical & Experimental Assessment Essentials | 剑桥 Year 7 物理：实验与实践考核要点
Practical work is a crucial part of the Year 7 Cambridge Physics course. You will be assessed not only on what you know, but on how you can plan, carry out, record and evaluate experiments safely. This guide covers all the key experimental skills you need to master, from reading a thermometer correctly to drawing a graph and drawing valid conclusions. Use it to build confidence in your lab work and to prepare for any practical test or investigation.
实验是剑桥 Year 7 物理课程的重要组成部分。考核标准不仅看你掌握了多少知识，更看重你能否安全地设计、操作、记录和评估实验。本指南涵盖了你需要掌握的所有核心实验技能，从正确读取温度计、绘制图表，到得出有效结论。利用这份指南来提升你的实验自信，并为任何实践测试或探究活动做好准备。
1. Lab Safety & Preparation | 实验室安全与准备
Before touching any equipment, always listen to your teacher's instructions. Tie back long hair, tuck in loose clothing and wear safety goggles when there is any risk of splashes, flying objects or hot liquids. In physics, you may work with hot water, masses, springs or electrical circuits – each has specific hazards. Never run in the lab, never taste anything, and report all breakages or spills immediately.
在接触任何器材之前，务必先听清楚老师的指导。将长发束起，整理宽松的衣角；当有液体飞溅、物体抛射或热液风险时务必佩戴护目镜。在物理实验中，你可能接触热水、砝码、弹簧或电路，每种器材都有特定的危险。严禁在实验室奔跑，绝不可品尝任何东西，如发生破损或溢出应立即报告。
- Always check that equipment is cool enough to touch before picking it up. / 拿起器材前，始终确认其温度是否降至可触碰。
- When using electrical circuits, never exceed the voltage your teacher has set and avoid short circuits. / 使用电路时，切勿超过教师设定的电压，并避免短路。
- Keep your work area tidy and only bring your lab notebook and a pen/pencil. / 保持工作区域整洁，只携带实验笔记本和笔。
2. Using Measuring Instruments | 使用测量仪器
Year 7 physics labs involve several common instruments. A metre ruler or tape measure can measure length in millimetres (mm) or centimetres (cm). A thermometer measures temperature in degrees Celsius (°C). A spring scale or forcemeter measures force in newtons (N). For electrical work, an ammeter measures current in amperes (A) and a voltmeter measures potential difference in volts (V). A stopwatch measures time in seconds (s). Always check the range and scale division before you start.
七年级物理实验涉及多种常用仪器。米尺或卷尺可用来测量以毫米或厘米为单位的长度。温度计测量摄氏温度 (°C)。弹簧秤或测力计以牛顿 (N) 为单位测量力。在电学实验中，电流表以安培 (A) 为单位测量电流，电压表以伏特 (V) 为单位测量电压。秒表以秒 (s) 为单位计时。开始测量前，务必确认仪器的量程与分度值。
- For a ruler, align your eye directly with the mark to avoid parallax. / 使用尺子时，视线应与刻度正对以消除视差。
- A thermometer's bulb must be fully immersed in the substance but not touching the container. / 温度计的液泡应完全浸入被测物，但不可接触容器壁。
- When using a stopwatch, start it on count of '3-2-1-go' to reduce reaction-time errors. / 使用秒表时，在 "三二一开始" 时启动，以减小反应时间误差。
3. Reading Scales & Minimising Errors | 读数与减少误差
ertainty. To get the most reliable data, learn to read scales to the nearest half division – al instruments, record all the digits shown. If you measure the same quantity several times, calculate the average (mean) to reduce the effect of random errors. Zero errors must be checked: does the ammeter read zero before you connect it? Does the forcemeter point to zero with no load?
任何测量都存在一定的不确定性。为了获得最可靠的数据，应学会估读到最小刻度的二分之一 —— 比如，带有毫米刻度的尺子可以读到 ±0.5 mm。数字式仪器则直接记录所有显示的数字。如果对同一量进行多次测量，应计算平均值以减小随机误差的影响。零点误差必须检查：接通电路前电流表读数是否为零？无负载时测力计指针是否指零？
Average (mean) = (sum of readings) ÷ (number of readings)
平均值 = (读数总和) ÷ (读数次数)
Anomalous results – readings that do not fit the pattern – should be identified and not used in the average. / 如果存在偏离整体趋势的异常读数，应予以识别并从平均值计算中剔除。
4. Planning an Investigation | 设计探究实验
A good investigation starts with a clear question and a prediction (hypothesis). Identify three types of variable: the independent variable (what you change), the dependent variable (what you measure) and the control variables (what you keep the same to make it a fair test). For example, when investigating the stretch of a spring, the force applied is the independent variable, the extension is the dependent variable, and you must use the same spring and room temperature as control variables. Write a numbered list of steps and a list of apparatus so someone else could repeat the experiment.
一项优秀的探究始于明确的问题与预测（假设）。需要确定三类变量：自变量（你改变的量）、因变量（你测量的量）和控制变量（为进行公平测试而保持不变的量）。例如，在研究弹簧的伸长时，施加的力是自变量，伸长量是因变量，而你必须使用同一根弹簧并保持室温不变作为控制变量。请写出带编号的操作步骤和器材清单，以便他人可以重复你的实验。
- Decide how many readings you will take and what range of the independent variable to cover. / 确定取多少组读数以及自变量的变化范围。
- Plan repeated readings to improve reliability. / 规划重复读数以提高可靠性。
5. Recording Data in Tables | 用表格记录数据
Before you start, draw a table with clear headings and units in brackets. Place the independent variable in the first column and the dependent variable in the second (or subsequent) columns. Include columns for repeated readings and the calculated average. For instance, in a spring extension experiment, your table might have columns: Force (N), Extension trial 1 (mm), Extension trial 2 (mm), Extension trial 3 (mm), Average extension (mm). Record all values neatly in ink, and do not scrub out mistakes – just draw a single line through and write the correct value beside it.
开始实验前先画好表格，表头应清晰注明括号内的单位。将自变量放在第一列，因变量放在第二列（或后续列）。表格中要包含重复读数栏以及计算出的平均值栏。比如，在弹簧伸长实验中，可设置这样几列：力 (N)、伸长量 1 (mm)、伸长量 2 (mm)、伸长量 3 (mm)、平均伸长量 (mm)。用墨水笔整洁地记录所有数值，不应用力涂抹错误 —— 只需用一条线划掉错误值，在旁边写上正确值即可。
6. Drawing Graphs | 绘制图表
e horizontal (x) axis and the dependent variable on the vertical (y) axis. Label each axis with the quantity and unit, e.g. 'Force (N)' and 'Extension (mm)' N or 2 N, but avoid awkward scales like 3 per square). Use small, neat crosses for data points, and draw a line of best fit – or smooth curve that passes through as many points as possible, ignoring obvious outliers.
图表能帮你发现规律。使用坐标纸和直尺绘制坐标轴。将自变量标在水平 (x) 轴上，因变量标在竖直 (y) 轴上。每个轴标注名称和单位，例如 "力 (N)" 和 "伸长量 (mm)"。选择合适的比例，使其占满半张纸以上且易于标绘（如每个大方格代表 1 N 或 2 N，避免使用如每格代表 3 这样的别扭比例）。用整齐的小叉号标记数据点，然后绘制一条最佳拟合线 —— 一条穿过尽可能多点、忽略明显异常点的单一直线或平滑曲线。
- A straight line through the origin shows that the variables are directly proportional. / 一条穿过原点的直线说明两变量成正比关系。
- If the line curves, it indicates a non-linear relationship. / 若线条弯曲，则表明是非线性关系。
7. Interpreting Results & Simple Calculations | 结果解读与简单计算
From your graph or table, you can describe the trend: does the extension increase as force increases? Is the increase steady or does it change? You may need to perform simple calculations using the data. In Year 7 physics, common formulas include the calculation of weight from mass, and the extension of a spring:
通过图表或表格，你可以描述变化的趋势：伸长量是否随力的增加而增加？增长是否稳定？你可能需要用数据做一些简单计算。在 Year 7 物理中，常见公式包括由质量计算重量，以及弹簧的伸长量：
Weight (N) = mass (kg) × gravitational field strength (≈ 10 N/kg)
重量 (N) = 质量 (kg) × 引力场强度 (≈ 10 N/kg)
Extension = new length – original length
伸长量 = 新长度 – 原长度
Always show the formula, substitute the numbers and give the answer with the correct unit. A final statement like 'As force doubled, extension also doubled, proving direct proportion' links data to conclusion. / 任何时候都要展示公式、代入数值，并给出带正确单位的答案。最后用类似的陈述——"当力增大一倍时，伸长量也增大一倍，证明成正比关系"——将数据与结论联系在一起。
8. Making Conclusions & Evaluations | 得出结论与评估
Your conclusion must answer the initial question and state whether the hypothesis was supported. Refer to the data: e.g. 'The graph shows a straight line through the origin, so the extension is directly proportional to the force up to 5 N.' Then evaluate the method. Were the control variables kept constant? Was the range of readings wide enough? Did you have any anomalous results? Suggest two specific improvements, such as 'Use a clamp stand to hold the ruler more firmly' or 'Take more readings at smaller force intervals'.
结论必须回答最初的问题，并说明假设是否得到了支持。要引用数据：例如 "图表显示一条过原点的直线，因此在 5 N 范围内伸长量与力成正比。" 然后对方法进行评估。控制变量是否保持不变？读数范围是否足够大？是否出现异常点？提出两条具体的改进建议，比如 "使用铁架台更牢固地固定尺子" 或 "以更小的力间隔增加读数次数"。
- An evaluation is not about saying 'I did it wrong' – it is about thinking like a scientist to make the experiment more trustworthy. / 评估并非意味着 "我做错了"，而是像科学家一样思考，让实验更值得信赖。
9. Key Experimental Skills: Forces and Extension | 核心实验技能：力与伸长
This classic experiment tests Hooke’s Law. Hang a spring from a clamp, measure its original length with a ruler. Add a known weight (e.g. 0.5 N), measure the new length and calculate the extension. Repeat for increasing loads up to a maximum safe limit to avoid permanent stretching. The independent variable is force, the dependent variable is extension. Control variables: same spring, same temperature. Plot a force-extension graph – a straight line through the origin confirms that extension is proportional to force within the elastic limit.
这个经典实验验证胡克定律。将弹簧悬挂在铁架台上，用尺子测量其原长。添加一个已知重量 (如 0.5 N)，测量新长度并计算伸长量。逐次增加负载，直至最大安全限度以避免永久变形。自变量是力，因变量是伸长量。控制变量：同一根弹簧、温度相同。绘制力-伸长量图像 —— 一条过原点的直线证实：在弹性极限内，伸长量与力成正比。
- Ensure you read the ruler at eye level and note the pointer of the spring clearly. / 确保视线与尺子水平，并清晰地读取弹簧指针。
- Add masses gently to avoid oscillation. / 轻轻添加砝码以避免弹簧晃动。
10. Key Experimental Skills: Electric Circuits | 核心实验技能：电路
Building working circuits helps you understand current, voltage and resistance. Start by drawing a circuit diagram using correct symbols. Connect a battery, switch, ammeter and a lamp or resistor in series. The ammeter must be placed in series to measure the current flowing through the component, while a voltmeter is always connected in parallel to measure the voltage across it. You might investigate how current changes when you change the resistance (by using different bulbs or resistors). Remember to open the switch between readings to avoid heating and to conserve battery.
搭建实际电路有助于理解电流、电压和电阻。首先用正确的符号画出电路图。将电池、开关、电流表和灯泡（或电阻）串联。电流表必须串联以测量流过元件的电流，而电压表始终并联以测量其两端电压。你可以探究电阻变化（通过使用不同的灯泡或电阻）时电流如何变化。记得在读数间隔断开开关，以避免元件发热并节省电池电力。
- Check that all connections are tight; loose wires cause intermittent readings. / 检查所有连接是否紧固，导线松动会使读数不稳定。
- Take current readings quickly and record them to 0.01 A if possible. / 快速读取电流值，如果可能，记录到 0.01 A。
11. Light Reflection Experiment | 光的反射实验
In this optics investigation, you verify the law of reflection: the angle of incidence equals the angle of reflection. Use a plane mirror placed upright on a sheet of paper, a ray box to produce a single narrow beam of light, and a protractor. Draw a normal line (a dashed line at 90° to the mirror’s surface) on the paper. Shine the beam along a given angle of incidence, mark the incident and reflected rays with pencil crosses, then remove the mirror and draw the rays. Measure both angles from the normal. Repeat for several angles and compare. Sources of error include aligning the ray exactly and judging the centre of the beam.
在这个光学探究中，你验证反射定律：入射角等于反射角。使用直立在纸板上的平面镜、光箱（发出一束细窄光线）和量角器。在纸上画一条法线（与镜面成 90° 的虚线）。让光线沿给定的入射角照射，用铅笔打叉标记入射光线和反射光线的路径，然后移开镜子并画线。从法线出发测量两个角度。对多个角度重复测量并比较。误差来源包括光线的精确对准以及对光束中心的判断。
angle of incidence (θᵢ) = angle of reflection (θᵣ)
入射角 (θᵢ) = 反射角 (θᵣ)
ther the difference is within ±2°, which could be acceptable due to reading uncertainty. / 如果结果显示角度接近但不完全相等，请讨论偏差是否在 ±2° 以内，这可能由于读数不确定性而被认为是可接受的。
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