Today I am going to show you how to make a barometer very easily. To make this you are going to need very basic items around you. So lets get started.
For this you will need the following things.
2)A glass jar.
3)A straw or broomstick.
Take a balloon and cut it in half. Discard the neck.
Now take the jar and open its cap.
Now take the jar and stretch the balloon and firmly cover the mouth of jar. Tape the edges to make it air tight.
Take the straw and stick on the balloon. One third of the stick should be hanging from the edge. Now tape it.
Now if you want you may colour it.
Keep the jar beside a wall . The stick on the balloon would be the pointer or indicator . Mark the place of the stick on the wall. Now after a few days if the stick goes downward you would be able to say that the air pressure has decreased and if it goes up then the air pressure has increased.
It is ready to use.
As air is trapped inside the balloon, when the pressure outside the jar decreases, the air inside expands to compensate for decrease in air pressure. So the balloon expands with the air inside the jar, and the center of the stick rises up, and the sticks edge goes lower. And it indicates decreased air pressure.