単位 3：物理学Iの実験技術
Pearson Edexcel · International A-Level · Physics トピック 3 13:08 英語ナレーション・英語＋中文字幕 burning-in
章
Transcript
Two groups report different wire diameters.
两组测得不同的导线直径。
The extra decimal places do not tell us which result is better.
小数位数更多并不能说明结果更好。
We need the instrument, its zero check, the contact method and the spread of repeated readings.
我们需要了解仪器、零点检查、接触方法和重复读数的分散程度。
This lesson follows that evidence chain, from a valid plan to a justified conclusion.
本课沿着从有效设计到有依据结论的证据链展开。
Written practice supports laboratory work; it does not replace it.
书面练习支持实验操作，但不能代替实验。
When changing string tension, frequency is the response.
改变弦的张力时，频率是响应量。
String length and linear density also affect that frequency.
弦长和线密度也会影响频率。
Naming length as a control is only the beginning. Say how you measure and maintain the same vibrating length.
仅仅写出控制弦长还不够，还要说明如何测量并保持相同的振动长度。
Keep the same mode too: changing harmonic can imitate a change caused by tension.
振动模式也必须保持一致，因为改变谐波可能被误认为张力改变的效果。
A useful method tells another student what to do.
一个可用的方法应让另一位学生能够照着操作。
Name the measuring instrument and choose a range that includes the expected readings.
明确测量仪器，并选择覆盖预期读数的量程。
Define positions or timing events precisely. Explain which settings are changed, which readings are recorded and how the calculation or graph answers the original investigation.
精确定义位置或计时起止事件，说明改变哪些设置、记录哪些读数，以及计算或图像如何回答原问题。
Add a precaution for the actual hazard.
安全措施必须针对真实的危险。
For the string fundamental, frequency squared is proportional to tension when length and linear density stay fixed.
弦长和线密度不变时，弦的基频平方与张力成正比。
Hang measured masses over a freely moving pulley so tension is approximately mass times gravitational field strength.
通过转动灵活的滑轮悬挂已知质量的砝码，使张力近似等于质量乘重力场强度。
Tune the fundamental at each setting and repeat the tuning.
每次调到基频共振并重复调节。
A straight line through the origin on this graph supports the model over the measured range.
图线在测量范围内近似通过原点，支持这一模型。
Close a micrometer correctly before measuring.
测量前正确闭合千分尺。
A positive zero reading must be subtracted from later indicated readings.
若零点读数为正，应从后续示值中减去这个偏移。
That checks one point on the scale.
这只是检查了刻度上的一个点。
Calibration compares against known references across the needed range.
校准需要在所需量程内与已知参考值比较。
A good zero reading alone cannot prove that every other reading is correct.
零点正确不能证明其他所有读数都正确。
Use the ratchet to keep contact pressure consistent.
使用棘轮保持接触压力一致。
Write a physical explanation before suggesting improvements.
先写出物理解释，再提出改进。
Ask whether the cell is in the same condition for every reading. Then propose two changes that target the cause.
想想每次读数时电池是否处于相同状态，然后提出两个针对原因的改变。
A phrase such as take more readings is not enough if every new reading comes from a changing system.
如果系统不断变化，增加读数并不能解决问题。
Pause and make your own three-point response.
暂停并写出自己的三点回答。
A downward trend is evidence of changing cell conditions, rather than only random variation.
持续下降表明电池状态在变化，而不只是随机波动。
Use a larger external resistance to reduce current. Open the switch between readings and allow conditions to stabilise. Repeats can then assess stability.
增大外接电阻以减小电流，在读数之间断开开关并让状态稳定，然后用重复读数检查稳定性。
Averaging a drift hides the change instead of fixing it.
对漂移直接取平均会掩盖变化，无法消除原因。
These are context-specific improvements with a physical reason.
这些改进都针对具体情境并有物理理由。
Imagine five very similar readings from a micrometer with an uncorrected zero error.
设想一把没有修正零点误差的千分尺给出五个非常接近的读数。
They are precise, but they may all be displaced from the true diameter.
这些读数精密，却可能全部偏离真实直径。
Repeating and averaging can reduce random variation. It cannot remove a shared systematic offset. Investigate and correct the cause instead of treating all error as scatter.
重复测量和取平均可以减小随机变化的影响，但不能消除共同的系统偏移，必须查明并修正原因。
Clustering within one group supports repeatability.
同一组内的读数集中，支持重复性。
Comparing a second group using another instrument examines reproducibility.
另一组使用不同仪器进行比较，是检查再现性。
A disagreement may come from zero offsets, contact pressure or sampling different positions on the wire.
差异可能来自零点偏移、接触压力，或测量导线的不同位置。
Compare the methods and instrument checks.
应比较方法并检查仪器。
The inconvenient group is evidence to investigate, not data to erase without a reason.
与预期不符的数据是需要调查的证据，不能无理由删除。
On this diagram, the last visible sleeve mark is four point five millimetres. Thimble division twenty-three aligns with the reference line, and each division is one hundredth of a millimetre.
图中最后露出的套筒刻度为四点五毫米，微分筒第二十三格与基准线对齐，每格为零点零一毫米。
This gives an indicated value before any zero correction.
这给出零点修正前的示值。
Read the diagram itself; a text extraction can omit the decisive scale mark.
必须直接读图，文字提取可能漏掉决定读数的刻度。
The indicated diameter is four point five plus zero point two three, giving four point seven three millimetres.
示值为四点五加零点二三，得到四点七三毫米。
With a positive zero error of zero point zero two millimetres, subtract that offset. The corrected value is four point seven one millimetres.
零点误差是正零点零二毫米，因此应减去该偏移，修正后为四点七一毫米。
The sign matters: the instrument was over-reading before the correction.
符号很重要，因为修正前仪器读数偏大。
A light gate records how long the beam is blocked.
光电门记录光束被遮挡的时间。
Dividing the interrupting length by that time gives a passage speed. It does not give acceleration.
用遮光片长度除以该时间，得到通过时的速度，而不是加速度。
For mean acceleration, obtain two speeds and the time between their corresponding events.
求平均加速度，需要两个速度及对应事件之间的时间。
With video, use known frame rate and clearly defined events; blur and unclear positions can still dominate uncertainty.
视频法需要已知帧率和明确事件，画面模糊及位置不清仍可能成为主要不确定度来源。
A display resolving hundredths of a second might give five point one two and five point two four seconds.
分辨到百分之一秒的仪器可能给出五点一二和五点二四秒。
Record the same decimal places for unchanged raw measurement conditions.
原始测量条件不变时，应保持相同小数位数。
Keep extra calculation digits internally, then round the result sensibly.
计算中保留额外数字，最后合理舍入。
An anomalous point needs a check or repeat where possible. Do not silently remove a reading because it spoils the expected line.
异常点应尽可能检查或重测，不能因为它破坏预期直线就默默删去。
For one reading, this specification uses half the instrument resolution as the basic absolute uncertainty. That does not mean the method is perfect.
本大纲对单次读数采用仪器分辨率的一半作为基本绝对不确定度估计，但这不代表方法完美。
Reaction time, alignment or a poorly defined endpoint can make the uncertainty larger.
反应时间、对准误差或终点不明确都可能使不确定度更大。
Divide absolute uncertainty by the measured value and multiply by one hundred to express a percentage.
绝对不确定度除以测量值，再乘一百，得到百分比不确定度。
Half of zero point one gram is zero point zero five gram.
零点一克的一半是零点零五克。
Divide this by one hundred thirty-five grams and multiply by one hundred. The percentage uncertainty is about zero point zero three seven percent.
将其除以一百三十五克并乘一百，得到约百分之零点零三七。
This estimate concerns the resolution contribution; a separate calibration problem would require separate investigation.
这是分辨率带来的不确定度估计；校准方面的问题仍需另外检查。
Calculate the mean without rounding it too early.
计算平均值时不要过早舍入。
Find the largest and smallest time, take their difference, then halve it. Compare this spread estimate with half a hundredth of a second.
找出最大和最小时间，相减后除以二，再与百分之一秒的一半比较。
Pause and decide which evidence matters here before continuing to the worked result.
暂停计算，并判断这里应依据哪一种证据估计不确定度，再看结果。
The sum is twenty point seven four seconds, giving a mean of five point one eight five seconds.
总和为二十点七四秒，平均值为五点一八五秒。
The range is zero point one two second, so half range is zero point zero six second.
极差是零点一二秒，半极差就是零点零六秒。
Dividing by the unrounded mean gives about one point two percent.
除以未舍入的平均值，得到约百分之一点二。
Half the display resolution is much smaller and would miss the observed scatter.
显示分辨率的一半远小于实际分散程度，无法描述已观察到的变化。
The specification explicitly excludes compounding percentage uncertainties from Unit Three.
大纲明确指出第三单元不要求合成百分比不确定度。
We therefore practise the required estimates and the interpretation of supplied uncertainties.
因此这里练习规定的估计方法，以及对题目给定不确定度的解释。
An uncertainty is an interval describing limited knowledge of a value. It is not necessarily a mistake, nor the known size of an error.
不确定度描述对数值认识有限而给出的区间，不一定是操作错误，也不是已知误差的大小。
Correct a known zero error separately.
已知零点误差需要单独修正。
Use a large part of the graph area with scales that are easy to subdivide.
使用图纸的大部分区域，选择容易细分的规则刻度。
Plot crosses carefully, then draw a thin best-fit line balancing scatter.
准确画出小叉，再画细的最佳拟合线，使两侧散点大致平衡。
Do not join noisy points into a zigzag.
不要将有噪声的数据逐点连成折线。
For direct proportionality, the fitted line must also be consistent with the origin. A non-zero intercept can have a physical meaning.
正比例关系还要求拟合线与通过原点相符，非零截距可能有物理意义。
Inspect the dashed triangle.
观察虚线三角形。
Its corners lie on the fitted line and span much of the plotted range. The changes are large compared with a small coordinate-reading uncertainty.
其顶点位于拟合线上，并跨越较大范围，因此坐标读数的不确定度相对于变化量较小。
A tiny triangle makes the same reading uncertainty a larger fraction of the result.
使用很小的三角形时，相同的读数不确定度占结果的比例更大。
The gradient needs units from both axes.
斜率单位必须由两个坐标轴共同确定。
Using the two indicated line points, resistance changes by three point two ohms while length changes by zero point eight metre. The gradient is four ohms per metre. Substitution gives an intercept of zero point four ohm.
由所示两个拟合线点，电阻变化三点二欧姆，长度变化零点八米，因此斜率为四欧姆每米。
Multiplying gradient by cross-sectional area gives resistivity.
代入得到截距零点四欧姆。 斜率乘横截面积得到电阻率。
Dividing one resistance by its length would incorrectly include the fixed offset.
用某一个电阻值直接除以长度，会错误地包含固定偏移。
A graph can have frequency in megahertz rather than hertz. Its numerical gradient then needs a factor of one million before SI substitution.
图的频率单位可能是兆赫而不是赫兹，代入国际单位制前，斜率数值需要乘一百万。
A frequency against sine-angle graph has frequency units in the gradient because sine is dimensionless.
频率对角度正弦值的图，其斜率具有频率单位，因为正弦值没有单位。
Read the supplied equation: the gradient may be speed divided by a wavelength, rather than speed itself.
必须阅读题目给出的方程，斜率可能是速度除以某个波长，并不直接等于速度。
If five-ohm resistance steps suggest a maximum near ten ohms, take finer steps around that region.
若每五欧姆取点显示峰值在十欧姆附近，就应在该区域用更细的间隔测量。
Repeating the same ten-ohm reading cannot reveal the peak between settings. Keep cell conditions steady.
反复测十欧姆不能找到设置之间的峰值，同时还应保持电池状态稳定。
For other experiments, target the actual problem: a set square for horizontal distance, shielding for changing background light, or repeated resonance tuning from both directions.
其他实验也要针对具体问题改进，例如用直角尺测水平距离、遮光以减小背景光变化，或从两个方向重复寻找共振。
Pause and calculate the full interval for a density of eight point nine zero grams per cubic centimetre with zero point nine percent uncertainty.
密度为每立方厘米八点九零克，不确定度百分之零点九。 先求完整区间，再与八点九四比较。
Compare it with eight point nine four, then say what agreement does and does not establish.
说明一致能支持什么，以及不能证明什么。
Zero point nine percent of eight point nine is about zero point zero eight gram per cubic centimetre.
八点九的百分之零点九约为零点零八克每立方厘米。 因此区间约为八点八二到八点九八。
The interval therefore runs from about eight point eight two to eight point nine eight. A proposed value of eight point nine four lies inside. The measurement is consistent with that value; it does not uniquely identify the material.
候选值八点九四在区间内，说明测量结果与之相符，但不能据此唯一确定材料。
Close the reference and answer these three prompts.
合上讲义，回答这三个问题。
Then use the planning sheet, the measurement sheet and the graph sheet in order.
然后依次完成实验设计、测量和图像练习。
Explain your choices as well as calculating values.
除了计算数值，也要解释自己的选择。
Practical papers inform these skills, while the original sheets provide supported practice.
实验试卷用于确定需要训练的技能，原创练习则提供逐步支持。
Keep a method, evidence and a justified conclusion connected in every response.
每个回答都应把方法、证据和有依据的结论联系起来。