Why, when shaking the medical thermometer of a glass mercury, the indication of the mercury column begins to fall: the principle of action, explanation

This article describes the principle of operation of a medical mercury glass thermometer.

A mercury thermometer for measuring temperature, although it is already considered the thermometer of the last century, but it is still one of the most accurate and correct. We all use it or used it, but few people thought about its principle of action. Why, when shaking a medical mercury glass thermometer, the column readings begin to fall? Look for an answer below.

The principle of operation of the medical thermometer of the glass mercury: what is based on?

The medical thermometer can be found in every house. It is used to measure the temperature of the human body. A mercury thermometer is considered the most accurate device in its purpose. All specialists in the field of medicine prefer to use it, thanks to the minimum error and cheapness. But on what is the basis of the principle of operation of the medical thermometer?

• The thermometer is a design consisting of a measurement scale, a tube and a tank with a mercury.
• All components are enclosed in a glass case that provides a vacuum and the safety of the contents.
• When measuring the temperature, the metal tip in which the reservoir is hidden is heated. Mercury, like any other substance, expands when heated.
• The excess heated mercury is pushed through the narrowed neck into the tube. The tube runs along the scale with gradation. The values \u200b\u200bof the indications are already visible there - this is body temperature.

Remember: Mercury is a poisonous substance and dangerous to health. Therefore, such a mechanism as a thermometer requires careful handling. Glass - fragile material, a fall can lead to a violation of the integrity of the body and the entrance of mercury into the environment.

Why, when shaking the medical thermometer, the readiness of the column of mercury begins to fall: an explanation

When measuring body temperature with a mercury thermometer, the indications always remain at the maximum value. This is caused by vacuum inside a measuring tube. But why, when shaking the medical thermometer, does the indication of the mercury column begin to fall? Here is the answer:

• When a person shakes the thermometer, the hand sets the direction along which the device and mercury are moving.
• Liquid metal has high acceleration. Due to the sharp stop of movement, the mercury continues to move by inertia and enters the storage tank through the narrowed neck.
• Return back, without exposure to strength, mercury cannot.

Important rules should always be remembered:

• Do not take up the metal nose of the thermometer - the readings will increase when the heat is transmitted by hand, the fragile element can be accidentally dropped, the wrong direction of movement will be given.
• When shaking, you need to tightly take up the rounded upper end, the container with mercury should be in the opposite side.
• The movements of the hand should be sharp and directed down from the elbow.

Interesting: The narrowed part of the container, the properties of mercury and the force of surface tension do not allow a colder substance than in the tank, to return back. Therefore, the temperature in the thermometer, if it is not used, will always be in one parameter.

“Shake the medical thermometer” - a glass mercury: why is this necessary?

Devices for measuring body temperature, in common people called thermometers, are electronic and liquid (most often mercury). Before measuring the temperature with a mercury thermometer, they always say: "Shake the medical thermometer" - Why do you need it? Here is the answer:

• Liquid thermometers are arranged so that they must be shaken in order to measure the temperature again.
• As soon as a person measured the temperature, the mercury is fixed at a certain point and remains in one place.
• This occurs due to the fact that mercury expands as a result of heating and from the tip of the thermometer enters the zone where the numbers are applied.
• Due to the narrow jumper after the measurement is completed, the liquid itself cannot get back.
• To do this, the medical thermometer must be shaken. Otherwise, you can begin to measure the temperature from the value of the last measurement and then the readings will be erroneous.

But, if the last dimension stopped at a mark not exceeding 36.0 degrees, then you can measure the temperature without shaking. Typically, the thermometer is shaken to a 34-35 degrees.

Video: The principle of operation of the liquid thermometer