The mercurial thermometer is made of glass and contains a mercury ball and a mercury column. The upper part of the mercurial thermometer is a glass tube, and the lower end is a glass bulb. The end mercury ball has different shapes and sizes depending on the measurement position, such as the mouth surface is elongated, the anal surface is short and round or distinguished by color.
When the temperature rises, the mercury expands and flows out of the bulging part and then into the hollow tubular part. Read the temperature value by the engraved mark on the thermometer. The connection between the spherical bulging part and the hollow tube at the bottom end is a compact design (blocking area). When the temperature rises, the mercury in the spherical part expands by heat and is forced to flow out of this concave part.
When the temperature drops, this compact design will prevent the mercury from flowing back to the spherical part, so the mercury in the hollow tube will not change. When the thermometer is measuring again, you need to shake the thermometer first to return the mercury in the hollow tube to the spherical part.
Place of Origin
The glass bulb at the lower end of the thermometer is in contact with the human body. Because the temperature of the human body is higher than that of the thermometer, the mercury in the glass bulb is affected by the heat transmitted from the body, expands in volume, and rises along the thin glass tube, directly to the temperature of mercury. The body temperature is the same.
The structure of the thermometer is very special. There is a very thin neck where the glass bulb and the thin tube meet. When the thermometer leaves the human body, the mercury becomes cold and shrinks, and the mercury column breaks at the neck, and the mercury on it cannot return. Therefore, the thermometer can continue to display the human body temperature after it leaves the human body.
The reason why the thermometer is shaken, and it must be shaken when the number is higher than 35°C before use, the purpose of the shake is to let the mercury retreat and connect with the mercury in the glass bulb at the neck, before it can be used normally.
The measurement principle of the mercury thermometer makes his measurement results more accurate and stable.
The overall material is light, and the dimension is little, which are convenient for carrying around.