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How to determine atmospheric pressure on a laptop. Atmospheric pressure in physics. The effect of low atmospheric pressure on a person

People of various professions should be aware of the concept of atmospheric pressure: doctors, pilots, scientists, polar explorers and others. It directly affects the specifics of their work. Atmospheric pressure is a quantity that helps predict and forecast the weather. If it rises, then this indicates that the weather will be sunny, and if the pressure drops, then this portends worsening weather conditions: clouds appear and precipitation occurs in the form of rain, snow, hail.

The concept and essence of atmospheric pressure

Definition 1

Atmospheric pressure is the force that acts on a surface. In other words, at each point in the atmosphere, the pressure is equal to the mass of the overlying column of air with a base that is equal to one.

The unit of atmospheric pressure is the Pascal (Pa), which equates to a force of 1 Newton (N) acting on an area of 1 m2 (1 Pa = 1 N/m2). Atmospheric pressure in metrology is expressed in hectopascals (hPa) with an accuracy of 0.1 hPa. And 1 hPa, in turn, is equal to 100 Pa.

Until recently, the millibar (mbar) and millimeter of mercury (mm Hg) were used as a unit of atmospheric pressure. Pressure is measured absolutely at all meteorological stations. In order to produce surface synoptic charts that reflect the weather conditions at a given time period, the pressure at station level is brought into line with sea level values. Thanks to this, it is possible to distinguish areas with high and low atmospheric pressure (anticyclones and cyclones), as well as atmospheric fronts.

Definition 2

The average atmospheric pressure at sea level, which is determined at a latitude of 45 degrees, at an air temperature of 0 degrees, is 1013.2 hPa. This value is taken as standard, it is called "normal pressure".

Atmospheric pressure measurement

We often forget that air has weight. Near the Earth's surface, the air density is 1.29 kg/m3. Galileo also proved that air has weight. And his student, Evangelista Torricelli, was able to prove that air affects all bodies that are located on the earth's surface. This pressure became known as atmospheric pressure.

The formula for calculating the pressure of a liquid column cannot calculate atmospheric pressure. After all, for this it is necessary to know the height of the liquid column and the density. However, the atmosphere does not have a clear boundary, and with increasing altitude, the density of atmospheric air decreases. Therefore, Evangelista Torricelli proposed a different method for determining and finding atmospheric pressure.

He took a glass tube about a meter long, which was sealed at one end, poured mercury into it and lowered the open part into a bowl with mercury. Some of the mercury spilled into the bowl, but most of it remained in the tube. Every day, the amount of mercury in the pipe fluctuated slightly. Mercury pressure at a certain level is created using the weight of the mercury column, since there is no air above the mercury in the upper part of the tube. There is a vacuum, which is called the "Torricellian void."

Remark 1

Based on the foregoing, we can conclude that atmospheric pressure is equal to the pressure of the mercury column in the tube. By measuring the height of the mercury column, you can calculate the pressure that mercury produces. It equates to atmospheric. If atmospheric pressure rises, then the mercury column in the Torricelli tube increases, and vice versa.

Figure 1. Atmospheric pressure measurement. Author24 - online exchange of student papers

Atmospheric pressure instruments

To measure atmospheric pressure, the following types of instruments are used:

station mercury cup barometer SR-A (for the range of 810-1070 hPa, which is typical for the plains) or SR-B (for the range of 680-1070 hPa, which is observed at high-altitude stations);
aneroid barometer BAMM-1;
barograph meteorological M-22A.

The most accurate and commonly used are mercury barometers, which are used to measure atmospheric pressure at meteorological stations. They are located indoors in specially equipped cabinets. Access to them is strictly limited for safety reasons: only specially trained specialists and observers can work with them.

More common are aneroid barometers, which are used to measure atmospheric pressure at meteorological stations and at geographical stations for route research. Often they are used for barometric leveling.

The M-22A barograph is most often used to fix and continuously record any changes in atmospheric pressure. They can be of two types:

in order to register the daily change in pressure, M-22AC is used;
in order to register the change in pressure within 7 days, M-22AH is used.

Device and principle of operation of devices

Let's start with a cup of mercury barometer. This instrument consists of a calibrated glass tube filled with mercury. Its upper end is sealed, and the lower end is immersed in a bowl of mercury. The cup of a mercury barometer consists of three parts, which are connected by a thread. The middle bowl has a diaphragm with special holes inside. The diaphragm makes it difficult for the mercury to oscillate in the bowl, thus preventing air from entering.

In the upper part of the cup mercury barometer there is a hole through which the cup communicates with air. In some cases, the hole is closed with a screw. There is no air in the upper part of the tube, therefore, under the influence of atmospheric pressure, the column of mercury in the flask rises to a certain height on the surface of the mercury in the bowl.

The mass of the mercury column is equal to the atmospheric pressure.

The next instrument is the barometer. The principle of its device is as follows: the glass tube is protected by a metal frame, on which the measurement scale in pascals or millibars is applied. The upper part of the frame has a longitudinal slot in order to observe the position of the mercury column. For the most accurate report of the meniscus of mercury, there is a ring with a vernier, which moves along the scale with a screw.

Definition 3

A scale that is designed to determine tenths is called a compensated scale.

It is protected from contamination by a protective cover. A thermometer is mounted in the middle part of the barometer in order to take into account the influence of the ambient temperature. According to his testimony, a temperature correction is introduced.

In order to eliminate distortions in the readings of the mercury barometer, a number of amendments are introduced:

temperature;
instrumental;
corrections for the acceleration of gravity depending on the height above sea level and the latitude of the place.

Aneroid barometer BAMM-1 is used to measure atmospheric pressure in surface conditions. Its sensing element is a block, which consists of three connected aneroid boxes. The principle of the aneroid barometer is based on the deformation of the membrane boxes under the action of atmospheric pressure and the transformation of the linear displacements of the membranes with the help of a transmission mechanism into the angular displacements of the boom.

The receiver is a metal aneroid box, which is equipped with a corrugated bottom and a lid, the air is completely pumped out of them. The spring pulls back the lid of the box and prevents it from being flattened by air pressure.

Figure 2. Confirmation of the existence of atmospheric pressure. Author24 - online exchange of student papers

Atmospheric pressure refers to the pressure of atmospheric air on the surface of the Earth and objects located on it. The degree of pressure corresponds to the weight of atmospheric air with a base of a certain area and configuration.

The basic unit for measuring atmospheric pressure in the SI system is the Pascal (Pa). In addition to Pascals, other units of measurement are also used:

Bar (1 Ba=100000 Pa);
millimeter of mercury (1 mm Hg = 133.3 Pa);
kilogram of force per square centimeter (1 kgf / cm 2 \u003d 98066 Pa);
technical atmosphere (1 at = 98066 Pa).

The above units of measurement are used for technical purposes, with the exception of millimeters of mercury, which is used for weather forecasts.

The barometer is the main instrument for measuring atmospheric pressure. Devices are divided into two types - liquid and mechanical. The design of the first is based on a flask filled with mercury and immersed with an open end in a vessel with water. The water in the vessel transmits the pressure of the column of atmospheric air to mercury. Its height acts as an indicator of pressure.

Mechanical barometers are more compact. The principle of their operation lies in the deformation of a metal plate under the action of atmospheric pressure. The deformable plate presses on the spring, and that, in turn, sets in motion the arrow of the device.

Effect of atmospheric pressure on the weather

Atmospheric pressure and its effect on the state of the weather varies depending on the place and time. It varies depending on the altitude above sea level. Moreover, there are dynamic changes associated with the movement of areas of high pressure (anticyclones) and low pressure (cyclones).

Changes in weather associated with atmospheric pressure occur due to the movement of air masses between areas of different pressure. The movement of air masses form a wind, the speed of which depends on the pressure difference in local areas, their scale and distance from each other. In addition, the movement of air masses leads to a change in temperature.

Standard atmospheric pressure is 101325 Pa, 760 mm Hg. Art. or 1.01325 bar. However, a person can easily tolerate a wide range of pressure. For example, in the city of Mexico City, the capital of Mexico with a population of almost 9 million people, the average atmospheric pressure is 570 mm Hg. Art.

Thus, the value of the standard pressure is determined exactly. A comfortable pressure has a significant range. This value is quite individual and completely depends on the conditions in which a particular person was born and lived. So, a sharp movement from a zone with a relatively high pressure to a lower one can affect the functioning of the circulatory system. However, with prolonged acclimatization, the negative effect disappears.

High and low atmospheric pressure

In high pressure zones, the weather is calm, the sky is cloudless, and the wind is moderate. High atmospheric pressure in summer leads to heat and droughts. In low pressure zones, the weather is predominantly cloudy with wind and precipitation. Thanks to such zones, cool cloudy weather with rain sets in in summer, and snowfalls occur in winter. The high pressure difference in the two areas is one of the factors leading to the formation of hurricanes and storm winds.

Around our planet there is an atmosphere that puts pressure on everything inside it: rocks, plants, people. Normal atmospheric pressure is safe for a person, but its changes can seriously affect health and well-being. To avoid possible troubles, scientists of different specialties study the effects of blood pressure on humans.

Atmospheric pressure - what is it?

The planet is surrounded by an air mass, which, under the influence of gravity, exerts pressure on all objects on Earth. The human body is no exception. This is what atmospheric pressure is, and speaking in a simpler and more understandable language: HELL is the force with which air pressure is exerted on the earth's surface. It can be measured in pascals, millimeters of mercury, atmospheres, millibars.

Atmospheric pressure under normal conditions

An air column weighing 15 tons presses on the planet. Logically, such a mass would have to crush all life on Earth. Why doesn't this happen? It's simple: the fact is that the pressure inside the body and normal atmospheric pressure for a person are equal. That is, the forces outside and inside are balanced, and the person feels quite comfortable. This effect is achieved due to gases dissolving in tissue fluids.

What atmospheric pressure is normal? Ideal blood pressure is considered to be 750-765 mm Hg. Art. These values are considered correct for domestic conditions, but they are not true for all areas. On the planet there are zones of low - up to 740 mm Hg. Art. - and increased - up to 780 mm Hg. Art. – pressure. People living in them adapt and do not feel any discomfort. At the same time, visitors will immediately feel the difference and for some time will complain of malaise.

Atmospheric pressure norms by region

For different parts of the globe, normal atmospheric pressure in mmHg is different. This is explained by the fact that the atmosphere affects the regions differently. The whole planet is divided into atmospheric belts, and even within small areas, readings may differ by several units. True, not sharp drops are rarely felt and are perceived by the body normally.

The normal atmospheric pressure for a person changes under the influence of various factors. It depends on the elevation of the area above sea level, average humidity and temperature. Over warm zones, for example, the compression of the atmosphere is not as strong as over cold ones. Altitude has a strong effect on pressure:

at 2000 m above sea level, a pressure of 596 mm Hg is considered normal. Art.,
at 3000 m - 525 mm Hg. Art.;
at 4000 m - 462 mm Hg. Art.

What atmospheric pressure is considered normal for a person?

It is necessary to determine blood pressure in ideal conditions: clearly above sea level at a temperature of 15 degrees. What is normal atmospheric pressure? There is no single indicator that is fair for all. What normal atmospheric pressure will be for one or another person depends on the state of health, living conditions, and hereditary factors. We can only say for sure that optimal blood pressure is one that does not cause harm and is not felt.

How does atmospheric pressure affect people?

Not everyone feels its impact, but this does not mean that the influence of atmospheric pressure on people is absent. Sharp drops, as a rule, make themselves felt. Blood pressure in the human body depends on the force of expulsion of blood from the heart and vascular resistance. Both indicators can fluctuate when changing cyclones and anticyclones. The reaction of the body to pressure surges depends on what is the normal atmospheric pressure for this person. Hypotensive patients, for example, react poorly to low blood pressure, and hypertensive patients suffer from an even greater increase.

High atmospheric pressure - impact on humans

The anticyclone is characterized by dry, clear and calm weather. Elevated blood pressure is accompanied by clear skies. Under these conditions, no temperature jumps are observed. Hypertension sufferers, especially the elderly, people suffering from diseases of the cardiovascular system, and allergy sufferers react most severely to high blood pressure. During anticyclones, cases of heart attacks, strokes, and hypertensive crises are more often recorded in hospitals.

You can understand that the pressure is elevated, knowing what is the normal atmospheric pressure for a person. If the tonometer shows a value that is 10-15-20 units higher than it, such blood pressure is already considered high. In addition, an increase in pressure is determined by symptoms such as:

headache;
pulsation in the head;
hyperemia of the face;
noise and whistling in the ears;
tachycardia;
ripples before the eyes;
weakness;
fast fatiguability.

How does low atmospheric pressure affect people?

The first to feel low blood pressure are the cores and people suffering from intracranial pressure. They feel general weakness, malaise, complain of migraines, shortness of breath, lack of oxygen, and sometimes pain in the intestinal area. The cyclone is accompanied by an increase in temperature and humidity. Hypotensive organisms react to this by dilating blood vessels with a decrease in their tone. Cells and tissues do not get enough oxygen.

The following signs are also considered characteristic of low atmospheric pressure:

rapid and difficult breathing;
paroxysmal spasmodic headache;
nausea;
prostration.

Meteorological dependence - how to deal with it?

This problem is complex and unpleasant, but it can be dealt with.

How to deal with weather dependence for hypotensive patients:

Healthy and long - at least 8 hours - sleep strengthens the immune system and makes it more resistant to changes in blood pressure.
Douches or regular contrast showers are suitable for training vessels.
Immunomodulators and tonics help improve well-being.
Do not expose the body to too much physical stress.
Be sure to include foods containing beta-carotene and ascorbic acid in the diet.

Tips for hypertensive patients are slightly different:

It is recommended to eat more vegetables and fruits, which contain potassium. Salt, liquids from the diet is better to exclude.
During the day, you should take a shower several times - light, contrasting.
Check blood pressure regularly and take if necessary
During the period of increased blood pressure, do not take on complex cases that require a high concentration of attention.
Do not climb to a high altitude during the period of a steady anticyclone.

Everyone knows that the formula for calculating the pressure of a liquid is as follows: p \u003d ρgh, where p is the pressure of the liquid on the bottom of the vessel, ρ is the density of water, g is the force of gravity acting on 1 kg, h is the height of the liquid column.

But in order to calculate atmospheric pressure using this formula, we need to know the height of the atmosphere and the density of the air. Since there is no definite boundary near the atmosphere, the calculation of atmospheric pressure using this formula is impossible.

How to measure atmospheric pressure? The Toricelli Experience

But how can it be measured then? In this we were helped by an Italian scientist who studied with Galileo, Evangelista Torricelli. He conducted an experiment where he took a glass tube about 1 m long, sealed at one end, and filled it with mercury. The other end of the tube was closed.

The tube was lowered with its plugged end into the bowl and opened, as a result of which part of the mercury poured into the bowl. The height of the mercury column turned out to be approximately 760 mm. There is an airless space between the top of the mercury column and the end of the tube.

But it would seem what is atmospheric pressure? And here's what: the atmosphere presses on the surface of mercury, while mercury is in equilibrium. It follows from this that the pressure of mercury in the tube at the level of the mercury surface in the cup is equal to atmospheric pressure.

If it is more, then mercury will pour out of the tube, if it is less, then mercury from the bowl will pass into the tube. from this experiment it follows that atmospheric pressure is equal to the pressure of mercury in the tube (p atm = p mercury).

Now, having measured the height of the mercury column, we can calculate the atmospheric pressure, which will be equal to: the density of mercury times the force of gravity acting on 1 kg times the height of the mercury column. This will be atmospheric pressure.

Atmospheric pressure in millimeters of mercury

Since in the Torricelli experiment, the higher the atmospheric pressure, the higher the mercury column in the tube, it has become customary to measure atmospheric pressure in millimeters of mercury (mm Hg). If the pressure is 760 mm Hg. Art., then the height of the mercury column in the tube will be equal to 760 mm, respectively.

Let's draw a parallel with the known unit of pressure measurement - pascal (Pa). So, the pressure is 1 mm Hg. Art. equals...

p \u003d gρh, p \u003d 9.8 N / kg * 13600 kg / m ^ 3 * 0.001m ≈ 133.3 Pa.

Equals 133.3 Pa, where 9.8 N / kg is the force of gravity acting on 1 kg 13600 kg / m ^ 3 is the density (ρ) of mercury, and 0.001 m is 1 millimeter of mercury.

In weather reports, you can hear that the atmospheric pressure is 1030 hectopascals (1030 hPa). This is the same as 760 mmHg. Art. and is normal atmospheric pressure.

It is no secret that atmospheric pressure is unstable and changes throughout the day. Often, this is due to changes in the weather.

Now no one measures the height of the mercury column in the tube with a ruler. To measure atmospheric pressure, a mercury barometer is used (from the Greek baros - gravity and metro - to measure). The simplest mercury barometer is obtained by attaching a vertical measuring scale to the mercury tube used in Torricelli's experiment.

Goals and objectives: to continue the formation of knowledge and ideas about the atmosphere; to analyze with students new concepts and definitions; consider the types, magnitude, causes of change and methods for measuring At. D.; prove to students the existence of At. D.; show integration with biology - plants-barometers; to form the ability to generalize, highlight the main thing, draw an analogy, identify cause-and-effect relationships; attach to geographical terms, form a conscious discipline.

Lesson form:

conversation, demonstration of experience proving the existence of At. D (a sheet of paper and a glass of water). Solution of practical problems according to At. D.

Lesson type:

explanation of new material.

Equipment:

aneroid barometer, glass of water, sheet of paper, textbook, atlas for grade 6.

Terms and concepts:

At. D., normal pressure, mercury barometer, aneroid barometer. Evangelist Torricelli explanatory-illustrative, reproductive, problematic.

DURING THE CLASSES

1. Organizational moment.

2. New topic after practical work.

Every substance has its own weight and mass, and even air. Air exerts pressure on all objects it comes into contact with, such as the experiment with a glass of water and a sheet of paper.

The mass of 1 m 3 of air above sea level is 1 kg 300 g

If we take a column of air from the earth's surface to the upper boundary of the atmosphere, it turns out that on 1 cm 2 of the surface, the air presses with the same force as a weight weighing 1 kg 33 g (1 m 2 \u003d 10,000 cm 2 x 1.33 \u003d 13 300 kg (13 t 300 kg)

Let's try to calculate the pressure exerted by the atmosphere on your palm.

The area of the palm is 60 cm 2 x 1.33 kg = 79.8 kg

Guys, why don't we or other living organisms feel the pressure that is pressing on us? (Because it is balanced by the internal pressure that exists inside the human body). So we have come to the definition - Atmospheric pressure is the force with which air presses on the earth's surface and all objects on it ( write in notebook).

And who measured and established what atmospheric pressure is?

In the 17th century The Italian scientist E. Torricelli proved that atmospheric pressure exists.

He conducted the following experiment: He took a tube 1 m high, soldered it from one end and poured mercury (this is a liquid poisonous metal Hg), turned the tube into a bowl with mercury and opened it, part of the mercury poured out, and part remained in the tube. If Atm. D. will weaken, then the mercury will pour out a little more, if it rises, then the column of mercury will rise.

What prevented mercury from pouring out completely? (Air pressure presses on the mercury in the cup and prevents the mercury from pouring out) as shown by the experiment with a glass of water.

Now let's turn to the textbook p. 144

It is established that normal Atm. D. is 760 mm Hg. at sea level at the 45° parallel (Fig. 72) write in a notebook.

How is Atm measured? D.?

Barometer (mercury) from the Greek baros - heaviness, meter - I measure. It is used at all meteorological stations, where, in addition, a barograph (graph-writing) is also installed.

Aneroid (without liquid) a box from which air is pumped out. If the pressure increases, the box shrinks; if it decreases, the box expands, the arrow shows the change in its volume.

If Atm. D. goes down - then this is to (to the rain)

If it rises, then it (for clear weather)

But how does atmospheric pressure change?

Let's look again at Fig. 72

Conclusion: means pressure will decrease with height. And after how many meters?

With height, the air becomes less dense, the oxygen in it decreases, and it becomes more difficult to breathe. Therefore, when a person climbs the mountains already at an altitude of 300 m, he begins to feel bad - there is shortness of breath, dizziness, nosebleeds.

Every 10.5 m Atm. D. decreases by 1 mm Hg. Art.

Atmospheric pressure also changes with temperature. Warm air is lighter (expands) - Atm.D. - low; cold air is heavier (compresses) Atm. D. - high.

In nature, there are plants that can feel the change in Atm.D. and predict the weather (clover, violet, adonis, field bindweed, white water lily - "Entertaining Biology" p. 83; take reproductions of flowers from a biology teacher).

Where can you use the material you are currently studying in class? (Student answers).

3. Fixing

Question number 2.

a) cold weather - Atm rises. D.

b) warm weather - the Atm decreases. D.

Question number 5. The height of Kazan according to the atlas is 200 m; latitude 54.5°N Need to know what is the pressure in Kazan? 200 m / 10.5 m = 19.04 mm; 760 mm - 19.04 \u003d 741 mm Hg

Problem: At the foot of the mountain at an altitude of 2300 m above sea level, the air pressure is 756 mm, and at the top of the mountain at the same time 720 mm. What is the relative and absolute height of a mountain?

756mm - 720mm = 36mm x 10.5m = 478m (relative height)

478 m + 200 m = 678 m (altitude)

Figure #1

Task: If at the foot of the mountain the pressure is 760 mm, then what will be the pressure at a height of 336 m?

336 m / 10.5 m = 32 mm;

760 mm - 32 mm = 728 mmHg

4. Homework:§ 38 question no. 3; #4