# Simple Barometers & Air Pressure

• belyzel4
In summary, the conversation discusses the relationship between surface area and air pressure in a simple barometer. It is explained that increasing the surface area of the barometer cup or the radius of the barometer tube would not affect the height of the mercury rising to 760mmHg. The pressure exerted by the atmosphere is not dependent on the mass of the object, but rather on gravity. Therefore, increasing the size of the barometer tube would not change the pressure exerted on the mercury.
belyzel4
Hey Guys! I need help with interpreting something regarding simple barometers. I believe I understand what is going on relatively well, but I am having trouble figuring out what is going on when I adjust something.

Mechanism: Barometer tube is a "vacuum" with no molecules inside of it. So when the Barometer with Mercury it is exposed to air pressure at sea level, the air pressure pushes down on the Mercury such that it is pushed through the tube up to a height of 760mm.

Question: If I increased the surface area of the barometer cup from let's say a given [..I..] to [...I...], would the increased surface area of Mercury that air pressure can push on increase the height that Mercury moves up beyond 760mmHg?
--> Considering Pressure is a force, wouldn't the increased surface area to exert a force on result in a stronger total force?

Question: If I increase the radius of the barometer tube from let's say [..I..] to [..III..], would Mercury still rise to 760mmHg? I am confused when asking this because I am trying to reason how a whole column/layer of water in the ocean exerts only 1 atm of pressure on a diver when he is 10m below the ocean. I think this has something to do with how 1 atm of air pressure makes a water barometer rise to 10.3m, but does that reasoning also apply to the 10m column/layer of the ocean? (I hope this made sense... I just want to know the relationship between why 10m below ocean is 1 atm when the width/radius of the ocean is beyond that of a barometer tube)

no,of course not,but for other reason...
pressure is the same,1 atm,doesnt matter the diameter of tube,but the mercury will fall due to his own weight,so it wouldnt rise at760 mm...
thats why such tubes have tiny diameter,for the weight not to count...
this pressure is made by gravity of the air,so gravity its the same,doesn`t matter the mass of the object,they are attracted with the same g to the earth...
if you understand this,you understand the pressure problem as well...

## What is a simple barometer?

A simple barometer is a scientific instrument used to measure air pressure. It typically consists of a glass tube filled with mercury, with one end open to the atmosphere and the other end sealed. As air pressure changes, it causes the mercury to rise or fall, indicating the current air pressure.

## How does a barometer measure air pressure?

A barometer measures air pressure using a principle known as "Boyle's Law". This law states that as the volume of a gas (in this case, air) decreases, the pressure of the gas increases. The mercury in a barometer is affected by changes in air pressure, causing it to rise or fall in the tube.

## What units are used to measure air pressure?

The most common unit of measurement for air pressure is the kilopascal (kPa). However, other units such as millibars (mb) and inches of mercury (inHg) are also commonly used. In some countries, air pressure may also be measured in hectopascals (hPa) or pounds per square inch (psi).

## What is considered "normal" air pressure?

Normal air pressure at sea level is typically around 101.3 kPa or 29.92 inHg. However, air pressure can vary greatly depending on weather patterns and altitude. As a general rule, air pressure decreases as altitude increases.

## How is air pressure related to weather?

Air pressure is closely related to weather patterns. High air pressure typically indicates clear and dry weather, while low air pressure often indicates stormy and wet conditions. Changes in air pressure can also affect wind patterns and temperature, making it an important factor in predicting weather.

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