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Air Pressure

Air Pressure. Just how does it work?. Things that effect Air Pressure. Altitude (Elevation) Temperature Humidity (moisture in the air). Altitude. The higher the altitude, the lower the air pressure. The lower the altitude, the higher the air pressure. Temperature.

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Air Pressure

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  1. Air Pressure • Just how does it work?

  2. Things that effect Air Pressure • Altitude (Elevation) • Temperature • Humidity (moisture in the air)

  3. Altitude • The higher the altitude, the lower the air pressure. • The lower the altitude, the higher the air pressure.

  4. Temperature • As the temperature goes up, the air pressure goes down. (hot molecules are further apart- less pressure). • As the temperature goes down, the air pressure goes up. ( cold air is more dense than warm air).

  5. Humidity • Humidity is the amount of moisture in the air. • Water vapor weighs less than air molecules. • As the air becomes more humid, the air pressure goes down (moist air weighs less than dry air). • Drier air has higher pressure because dry air weighs more than moist air, therefore it has greater pressure.

  6. Atmospheric Pressure Gas pressure depends on both density and temperature. Adding air molecules increases the pressure in a balloon. Heating the air also increases the pressure.

  7. Air pressure is equal in all directions. Air pressure = the force of air molecules pushing on an area.

  8. Barometric pressure goes down. As elevation goes up This is an inverse relationship.

  9. A Barometer is used to measure air pressure.

  10. In 1643, Evangelista Torricelli invented the barometer

  11. Torricelli’s barometer used a glass column suspended in a bowl of mercury. The pressure of the air molecules pushed the mercury up into the glass tube. The weight of the mercury in the tube was equal to the weight of the air pressing down on the mercury in the dish.

  12. As atmospheric pressure increases… The mercury in the tube rises.

  13. The Mercury Barometer Good: Bad: • Simple to construct • Highly accurate • Glass tube is fragile • Mercury is very toxic!

  14. The AneroidBarometer • No fragile tubes! • No toxic chemicals! • No batteries! • Never needs winding!

  15. MILLIBARS An aneroid barometer uses a cell which has had most of the air removed. As the air pressure around the cell increases, it presses on the cell, which causes the needle to move. Television weather forecasters usually give barometric pressure in inches of mercury. However, meteorologists measure atmospheric pressure in millibars.

  16. Changing Pressure A rising barometer = increasing air pressure. This usually means: Rising barometer readings indicate that a high pressure system is approaching. Higher atmospheric pressure is usually associated with fair weather and clearing skies.

  17. Changing Pressure A falling barometer = decreasing air pressure. This usually means: Falling barometer readings usually indicate the approach of an area of low pressure. Low pressure readings are usually associated with storm systems. Tornadoes and hurricanes can produce very low barometric readings.

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