What is atmospheric pressure, definition of atmospheric pressure

The earth is surrounded by a thick layer of air, which is known as the atmosphere. Air can flow as freely as water, and it is also subject to gravity. Hence there is pressure in the interior of the air in all directions, and this pressure is known as atmospheric pressure.

In 1654, Glick conducted the famous Magdeburg hemispheric experiment in Magdeburg, Germany, which gave people a deep understanding of atmospheric pressure, but it is not clear how much atmospheric pressure there is. Eleven years later, the Italian scientist Torricelli filled an 80-centimeter-long thin glass tube with mercury and placed it upside down in a tank containing mercury, and found that the mercury in the glass tube dropped by about 4 centimeters and then stopped falling. This 4 cm space has no air entering and is a vacuum.

Torricelli deduced from this that the pressure of the atmosphere was equal to the length of the mercury column. According to the pressure formula, scientists accurately calculated that atmospheric pressure is atmospheric pressure in the standard state.

1.Atmospheric pressure.

1) Atmospheric pressure: The pressure generated by the action of gravity in the atmosphere is called atmospheric pressure, referred to as atmospheric pressure. The famous experiment in history that proved the existence of atmospheric pressure was the Magdeburg Hemispheric Experiment

2) The reason for the formation of atmospheric pressure: Because air, like liquid, is subject to gravity and is fluid, there is pressure inside the air in all directions This is the reason why atmospheric pressure is generated

3) Measurement of atmospheric pressure: The first experiment in history to determine the value of atmospheric pressure was the Torricelli experiment

The method and principle of the experiment: the glass tube with a length of about 1m and a closed end is filled with mercury, the nozzle is blocked, and then it is inserted upside down in the mercury tank, when the finger that blocks the nozzle is released, the mercury in the glass tube will fall due to gravity, but the mercury in the tube only drops some, which is due to the fact that after the mercury in the tube falls, there is no air above the mercury surface in the tube, and there is a vacuum, and the mercury in the mercury tank has the effect of atmospheric pressure, and the mercury column in the tube is supported by atmospheric pressure The pressure generated by the mercury column at a certain height in the tube is equal to the atmospheric pressure, so the pressure generated by the mercury column is calculated according to the formula of liquid pressure, which is the magnitude of the atmospheric pressure.

Atmospheric pressure: 1The presence of atmospheric pressure.

The pressure in the atmosphere is multiplied by 10 to the 5th power of the PA in the standard state

The pressure of the atmosphere is in the standard state.

The layer of air that surrounds the earth is called the atmosphere, and the air is surrounded by gravity that surrounds the entire earth. The weight of the air, the pressure generated on the object is referred to as atmospheric pressure, the air is composed of extremely small gas molecules, with a certain volume and weight, when the pressure is one atmosphere, the temperature is 273 degrees k, the number of molecules contained in any gas in 1 cubic centimeter is one. The reason why we don't feel the pressure in the atmosphere is because there is air inside and outside the body, and the pressure on the inside and outside cancels each other out, like a piece of tissue paper stretched on a shelf; A single finger can pierce a large hole, but if both sides of the paper are pressed against the finger, it will not be damaged with a lot of force.

The pressure exerted on an object is about one kilogram per square centimeter, so we say that the pressure of the atmosphere is one atmosphere.

The definition of atmospheric pressure is the pressure exerted by the atmosphere on the object immersed in it.

Atmospheric pressure (abbreviated as atmospheric pressure or barometric pressure) refers to the pressure exerted by the atmosphere on an object immersed in it.

In 1654, Glick conducted the famous Magdeburg hemispheric experiment in Magdeburg, Germany, which strongly proved the existence of atmospheric pressure, which gave people a deep understanding of atmospheric pressure.

However, as early as 1643, the Italian scientist Torricelli filled a 1-meter-long thin glass tube filled with mercury (mercury) and placed it upside down in a tank containing mercury, and found that the mercury in the glass tube dropped to a height of about 760 mm and then stopped falling. The space above this 760 mm scale has no air entering and is a vacuum.

Torricelli deduced that the pressure of the atmosphere was equal to the pressure generated by the mercury column, which is known as Torricelli's experiment. The standard atmospheric pressure is: Pascal), which is equal to the pressure produced by 760 mm Hg.

Causes of atmospheric pressure:

The earth is surrounded by a thick layer of air, which is mainly composed of nitrogen, oxygen, carbon dioxide, water vapor and helium, neon, argon and other gases. It is densely distributed around the earth, with a total thickness of 1,000 kilometers, and all objects immersed in the atmosphere are subjected to the pressure of the atmosphere acting on it, just as objects immersed in water are subjected to the pressure of water. The reason why atmospheric pressure is generated can be explained from different angles:

1. The air is affected by gravity, and the air is fluid, so there is pressure in all directions. To put it in more detail, due to the attraction of the earth to the air, the air is pressed on the ground, and it has to rely on the ground or other objects on the ground to support it, and these objects that support the atmosphere and the ground are subject to the action of atmospheric pressure. The atmospheric pressure per unit area is the atmospheric pressure.

2. It can be explained from the point of view of molecular motion, because gas is composed of a large number of molecules that move irregularly, and these molecules are bound to constantly collide with objects immersed in the air, and each time the gas molecules collide with each other, they must give an impact force to the surface of the object, and the result of the continuous collision of a large number of air molecules is reflected in the pressure of the atmosphere on the surface of the object, thus forming atmospheric pressure.

If there are more molecules per unit volume, the more air molecules collide with the surface of the object in the same amount of time, and the resulting pressure will be greater.

The pressure exerted by the atmosphere on the object immersed in it is called atmospheric pressure, or atmospheric pressure or barometric pressure for short.

Atmospheric pressure refers to the pressure of the air at a certain location on the earth, and the air on the surface of the earth is subjected to gravity, resulting in atmospheric pressure The density of the air layer above the earth is not equal, the air near the surface layer is denser, and the air in the upper layers is thin and less dense Since the atmospheric pressure is generated by air gravity, where the height is large, the height of the air column above it is small, and the density is also small, so the higher the distance from the ground, the smaller the atmospheric pressure Usually under rock conditions, below 2 kilometers, For every 12 meters of altitude, the atmospheric pressure decreases by 1 mm of mercury

Both gases and liquids are fluid, and their pressures are similar, the atmospheric pressure is in all directions, and the atmospheric pressure in all directions is equal at the same location. However, since the density of the atmosphere is not uniform, the liquid pressure formula cannot be applied to the calculation of atmospheric pressure

The pressure of the gas that is sealed in a container is generated by the continuous collision of a large number of gas molecules in irregular motion against the container wall, and its magnitude is not determined by the gravity of the enclosed gas

Atmospheric pressure formula: p= gas gh