📚 Thermometers | 温度计
Thermometers are essential measuring instruments in physics. They determine temperature by observing a physical property that changes in a predictable way with thermal energy.
温度计是物理学中重要的测量仪器。它们通过观察某种随热能发生可预测变化的物理属性来测定温度。
In the A-Level CIE Physics syllabus, you need to understand the principles of thermometry, fixed points, temperature scales, and the advantages and limitations of different types of thermometer.
在 A-Level CIE 物理大纲中，你需要理解测温原理、固定点、温标以及不同类型温度计的优点与局限性。
1. Temperature and Thermal Equilibrium | 温度与热平衡
Temperature is a macroscopic physical quantity that determines the direction of net heat transfer between two bodies placed in thermal contact.
温度是一个宏观物理量，它决定两个热接触物体之间净热量传递的方向。
Heat always flows naturally from a body at a higher temperature to a body at a lower temperature, never the reverse.
热量总是自然地从温度较高的物体传向温度较低的物体，而不会自发反向传递。
When two objects reach the same temperature and no net heat transfer occurs between them, they are said to be in thermal equilibrium.
当两个物体达到相同温度并且彼此之间不再有净热量传递时，我们就说它们处于热平衡。
The zeroth law of thermodynamics states that if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. This law allows thermometers to be used consistently.
热力学第零定律指出，如果两个系统分别与第三个系统处于热平衡，那么这两个系统彼此也处于热平衡。这一定律使温度计能够被一致地使用。
2. Defining Temperature Scales | 温标的定义
A temperature scale requires two main things: a thermometric property and fixed points.
建立一个温标需要两个主要条件：一个测温属性和若干个固定点。
The thermometric property is a physical quantity that changes continuously and reproducibly with temperature. Common examples are length of a liquid column, electrical resistance, gas pressure at constant volume, and thermocouple emf.
测温属性是指随温度连续且可重复变化的物理量。常见的例子包括液柱长度、电阻、定容气体压强以及热电偶电动势。
The fixed points are reproducible temperatures to which numerical values are assigned. Historically, the Celsius scale used the ice point and the steam point.
固定点是被赋予数值的可复现温度。历史上，摄氏温标使用冰点和汽点作为固定点。
On the Celsius scale, the interval between the ice point and the steam point was divided into 100 equal degrees, giving 0 °C and 100 °C respectively.
在摄氏温标上，冰点与汽点之间的间隔被等分为 100 度，分别对应 0 °C 和 100 °C。
3. Celsius and Thermodynamic Scales | 摄氏温标与热力学温标
The thermodynamic temperature scale is the fundamental temperature scale in physics. Its unit is the kelvin, symbol K, not °K.
热力学温标是物理学中的基本温标。其单位是开尔文，符号为 K，而不是 °K。
The thermodynamic scale is independent of the properties of any particular substance, which makes it ideal for scientific work.
热力学温标不依赖于任何特定物质的属性，因此非常适合科学研究。
The conversion between Celsius temperature θ and Kelvin temperature T is:
摄氏温度 θ 与开尔文温度 T 的换算关系为：
T (K) = θ (°C) + 273.15
This means a temperature interval of 1 °C has exactly the same size as an interval of 1 K.
这意味着 1 °C 的温度间隔与 1 K 的温度间隔大小完全相同。
Absolute zero is the lowest possible temperature, 0 K or −273.15 °C. At this temperature, particles have the minimum possible internal energy; they still have zero-point energy according to quantum mechanics.
绝对零度是理论上可能的最低温度，即 0 K 或 −273.15 °C。在此温度下，粒子具有最低可能的内能；根据量子力学，它们仍具有零点能。
4. Fixed Points and Calibration | 固定点与校准
Calibration is the process of marking a scale on a thermometer using known fixed points.
校准是利用已知固定点在温度计上标定刻度的过程。
The ice point is the temperature at which pure ice and air-saturated water are in thermal equilibrium at standard atmospheric pressure.
冰点是在标准大气压下，纯冰与空气饱和水达到热平衡时的温度。
The steam point is the temperature at which pure water boils at standard atmospheric pressure. Both fixed points depend on external pressure, so they are not perfectly reproducible.
汽点是在标准大气压下纯水沸腾时的温度。这两个固定点都依赖于外部压强，因此并非完全可复现。
The triple point of water is the unique condition at which ice, liquid water, and water vapour coexist in equilibrium. It is assigned the exact value 273.16 K, making it highly reproducible.
水的三相点是冰、液态水和水蒸气三相共存时的唯一状态。它被赋予精确值 273.16 K，因此具有很高的复现性。
To calibrate a liquid-in-glass thermometer, place it in melting ice, mark the liquid level, then place it in steam above boiling water, mark the second level, and divide the interval into equal parts.
要校准一支玻璃液体温度计，可将其放入正在融化的冰中并标记液面，再放入沸水上方的蒸汽中标记第二个液面，然后将该间隔等分。
5. Properties of a Good Thermometer | 理想温度计的性质
A good thermometer should have a thermometric property that varies linearly with temperature. This makes the scale easy to calibrate and read.
一个好的温度计应具有随温度线性变化的测温属性。这使刻度易于校准和读取。
Sensitivity is the change in output reading per unit change in temperature. A larger change in the thermometric property for a small temperature change means higher sensitivity.
灵敏度是指单位温度变化所对应的输出读数变化。温度变化很小时，测温属性变化越大，灵敏度越高。
Range is the interval between the minimum and maximum temperatures that the thermometer can measure accurately and safely.
量程是温度计能够准确且安全地测量的最低温度与最高温度之间的范围。
Response time is the time taken for the thermometer to reach thermal equilibrium with its surroundings. A small thermal capacity usually gives a shorter response time.
响应时间是温度计与周围环境达到热平衡所需的时间。热容量小通常意味着响应时间较短。
Stability means the thermometer gives the same reading under the same conditions over time, without significant drift.
稳定性是指温度计在相同条件下长时间使用时能够给出相同读数，不会出现明显漂移。
6. Liquid-in-Glass Thermometers | 玻璃液体温度计
A liquid-in-glass thermometer consists of a thin-walled glass bulb attached to a narrow capillary tube. The bulb contains a liquid that expands more than the glass when heated.
玻璃液体温度计由一个薄壁玻璃泡和与其相连的细毛细管组成。玻璃泡内的液体在受热时膨胀程度比玻璃更大。
Mercury is commonly used because it has a uniform expansion, good thermal conductivity, and remains liquid over a useful range from about −39 °C to 356 °C.
水银常被使用，因为它膨胀均匀、导热性好，并且
Published by TutorHao | A-Level Physics Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图