Atmospheric Pressure

  • Anither term to indicate Air Pressure
  • Pressure due to the layer (column) of air ating down on Earth
  • Air pressure is measured with an instrument called a Barometer
  • The standard air pressure at sea level is 101.3 KPa

A picture of a barometer used to measure air pressure.

Air pressure can be used as an indcator f weather conditions.

High Pressure usually tends to indicate Fair weather conditions:

  • Dry,
  • Low density clouds,
  • Rising warmer  air

Low Pressure indicates Poor Weather Conditions:

  • Cold falling air masses
  • High density darker clouds
  • Rainy, Wet Weather

Here is a simplified diagram of a Barometer:  

The needles are attached to a sensittive, spring-suspended metal membrane.

As the air pressure increases, it presses down on the membrane and the needle moves clockwise.  When the airpressure decreases, the membrane pushes up activated by the spring and the needle moves in a counterclockwise direction.


Experiment to Demonstrate Air Pressure

This simple experiment demonstrates Air Pressure.

As the flame of the candle consumes the air in the inverted jar, it will eventually go out.  True?

  • Can you predict what will happen next?
  • Can you explain why?

Check your answer here >>>