Shulou(Shulou.com)11/24 Report--

Recently, the weather is getting hotter and hotter. The thermometer on the wall shows that it is 35 degrees Celsius. It needs to turn on the air conditioner to cool down. After a while, the temperature drops. The thermometer shows that the temperature is 25 degrees Celsius.

We will dress according to the temperature, but also according to the temperature to judge whether the body is healthy, it can be said that we pay attention to the temperature all the time.

Photo Source: pixabay, but we often have a lot of questions about temperature, for example, the units of temperature are degrees Celsius, Fahrenheit and Kelvin, and all kinds of thermometers directly measure the temperature. What is the temperature? let's learn about the secrets about temperature today.

The temperature is the physical quantity of the cold and hot degree of the object, but it is different from other physical units, for example, the speed can be seen through the naked eye, the area can be seen through the naked eye, and the temperature needs to be felt by the human body to get the result.

When the temperature is high under the sun, we will feel hot, while when the temperature is low in rainy days without the sun, we will feel cold, and if the temperature is high near the fire source, it will be hot. There are many such examples in daily life, which shows that there is a direct relationship between temperature and heat.

In fact, heat is a form of energy, and matter becomes hot when it absorbs heat, such as boiling water. When water absorbs heat, it becomes hot with the increase of temperature. On the contrary, when matter loses heat, it becomes cold, such as putting water in the refrigerator. When the temperature drops, the water becomes cold without heat.

Therefore, temperature is a form of internal heat energy, and the size of heat energy directly determines the temperature.

Temperature unit in daily life, the temperature unit we often use is Celsius, and we occasionally hear another temperature unit, that is Fahrenheit, and the international temperature unit Kelvin. What is the difference between these three temperature units?

℃ was proposed and named by the Swede Celsius. It takes water as the temperature measuring material, and sets the freezing point of water at 0 degrees and the boiling point at 100 degrees Celsius.

℉ is named after Warren Haight, the inventor of the mercury thermometer. It uses ice water and ammonium chloride as the temperature measuring material. It sets the freezing point of water at 32 degrees and the boiling point at 212 degrees.

The formula for converting degrees Fahrenheit to degrees Celsius is (- 32 degrees Fahrenheit) / 1.8, which is not convenient to use, so only a few countries such as the Bahamas and Palau still use degrees Fahrenheit.

Kelvin (K) is the international unit of temperature, which sets the boiling point of water at 373.15K and the freezing point at 273.15K, and the temperature as the starting point for calculation, that is, 273.15K is equal to the commonly used 0 degrees Celsius, so the difference between Kelvin and our commonly used degrees Celsius is 273.15 degrees Celsius. If 5 degrees Celsius translates to Calvin temperature is 273.15 degrees 5.

There are also Lancelot and Lehr degrees, both of which are no longer in use.

The history of thermometers humans began to explore the method of measuring temperature very early. Although they did not know what the temperature was at that time, they could use the body to feel it (mainly cold and warm), the growth of plants and the cold and hot changes in the environment to define the temperature. Even smelters will judge the temperature in the furnace by observing the color of the flame.

The first real thermometer was invented by Galileo. Its structure is relatively simple. The first thermometer is made by adding water and floating matter to a slender glass tube with a ball and inserting it into a glass bottle full of water.

Later, Sankerto, a student in Galileo, further improved the thermometer and engraved many scales on the slender glass tube so that the temperature could be measured and read more accurately.

The liquid in the thermometer has also developed from water, water-salt mixture to alcohol and mercury, and there are also electronic thermometers, infrared thermometers and so on, which measure the temperature more accurately.

The principle of a thermometer although the cold and heat of an object can be distinguished by feeling, it is still impossible to accurately know the temperature of the object, and using the body to come into contact with low or high temperature objects may also harm the skin, so, this requires the use of tools to measure temperature.

We all know that to measure body temperature, we only need to put the thermometer under the armpit, and then take out the scale on the thermometer to know the temperature of the human body.

In the measurement, we observe the height of the liquid level in the thermometer, thus knowing the temperature of the human body, so the thermometer can convert the temperature that is not easy to observe into a length that can be easily observed by the naked eye, which is called the transformation method in physics.

This method is the principle of the thermometer, which uses the thermal expansion and cold contraction of the liquid. There is a vacuole at the bottom of the thermometer, which contains alcohol liquid and is connected to a hollow tube.

When part of the thermometer vacuole touches the skin, the heat of the skin is transferred to the vacuole, and the alcohol liquid expands and rises along the thin tube, and we can measure the temperature of the human body according to the height of the alcohol liquid.

Does the thermometer measure the temperature directly? from the principle of the ordinary glass rod thermometer, we can see that it is not the temperature measured directly, but the length of alcohol or mercury liquid converted by thermal expansion and cold shrinkage, so as to let us know the specific temperature.

There is also the infrared thermometer I often use, which is also not a direct measurement of temperature. No matter what object in the world has thermal radiation, and because the higher the temperature, the stronger the thermal radiation, there is no need to directly contact the infrared thermometer of the measured object. It is the use of optical detectors to compare the reflected infrared light of different wavelengths with the built-in infrared light, and finally the results will be displayed digitally.

Obviously, like the glass rod thermometer, the more advanced infrared thermometer does not measure the temperature directly, it measures the thermal radiation of the object.

Therefore, the various thermometers we use do not measure the temperature directly, it uses thermal balance to change the temperature from one state to another, so that we can see the actual temperature.

Although the thermometer is not a direct measurement of the temperature, but the role and significance of the thermometer is very important, with the thermometer can measure the temperature more accurately.

In medicine, thermometers can help doctors judge the condition more accurately and effectively protect health and life safety; in science, with thermometers, more experiments can be carried out, thus promoting the rapid development of science and technology such as thermodynamics.

The picture is taken from Youtube "The First Celsius Thermometer", "Temperature Scales" and "How Do We Tell Temperature".

Gif is intercepted from Youtube "How Do We Tell Temperature" in this article.

This article is from the official account of Wechat: manufacturing principle (ID:zhizaoyuanli), author: Lao Zheng

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