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Make a Barometer - (Easy Science Project)

A barometer is a really interesting measuring device. And it is really easy to make. You can make one with just a few found around the house materials. In this tutorial I show you how to make a barometer and give you all the information you need so you understand how it works and why.



Here is a picture of the barometer we will make in this tutorial. All it takes is a jar or can, a couple of straws, a balloon, a rubber band and some glue/tape. That's it!

Home Make Barometer


Barometer in Hurricane IreneDoes this home made barometer really work? You bet it does! Just two days ago Hurricane Irene came through where I live in New England. And this is a picture of What happened to the barometer. Look at the massive bulging out of the balloon. This is because the Hurricane brought very low pressure. And the pressure inside the jug is just bursting out!




Ok, let's make this barometer - step by step

Typical containersFirst get yourself a container. It has to be glass or strong metal. It should not be something that crumples easily like a water bottle. And it should have a wide mouth.

In the picture we see three containers. The glass quart jar is great and the large can of beans is great too. The smaller can of soup is too small.




Balloon and glove

Now let's make the diaphram that stretches over the top of the container. For this you can use either a balloon or a latex glove. If you have a choice then go with the balloon. It will be a bit more durable.

Try to get twelve inch balloons. If you can't then nine inch balloons will work. It usually says on the package the size of the balloon.




Cut the balloon

Cut the balloon something like this. If you are using the glove then cut a big piece out of the hand part.






Stretch balloon over container

Stretch the balloon over the mouth of your container. Get it pretty tight.








Put a rubber band on tight

Wrap a couple of rubber bands around the balloon so it makes a nice tight fit on the mouth of the jug. The balloon should be pretty taut and the rubber bands good and tight. We don't want any leakage of air out of this jug.







Now let's make the arm of the barometer

Make the tip Cut yourself a piece of paper or cardboard so it looks like the purple arrow shown here. Insert it into the end of a straw.

Cut the size of the arrow so it is a snug fit in the straw. It is ok if the straw is distorted.





The barometer arm You could go ahead and use this straw as the arm of your barometer but the longer the arm the more accurate the reading. So go ahead and assemble two straws together to make one longer straw.






Cut the strawCut the other end of your straw assembly something like this. This way the glue and tape will hold better.









Apply Glue

Put a drop of white glue right in the center of the stretched balloon.








Tape the straw

Put the end of the straw onto the glue dot then apply a piece of tape over it all as shown in the picture.

The reason why we use both tape and glue is that the tape will just hold for a little while to allow the glue to set. In a couple of days the tape will tend to peel off but by then the glue will be set.






THe barometer wall chart

Put the barometer near a wall and tape up a piece of paper where the needle is. Mark a longish line where the needle points so you know right where it is now. And put a few smaller lines above and below.

Now as the barometric pressure changes you will see that needle move up and down! Voila, you have made a barometer.

As that needle goes up it means the weather is clearing. And as that needle goes down it means there is a storm moving in.


How a Barometer Works

The following picture shows you how the barometer works.

You start out with a jar of air right? Sounds funny but yes! And when you strretch a piece of rubber over it you capture that air in the jar. At the time you did this the air pressure inside and outside are exactly the same. But the outside air pressure is going to change with the weather.

Let's say some clear and sunny weather is moving in. This will be a raise in the air pressure around you. And this will push down on the balloon. And because we have made a little lever out of straws this will push the end with the arrow up!

The same thing happens in the opposite direction too. If a storm is moving in the outside air pressure drops and this causes the higher pressure inside the jug to bulge the balloon out. And this would cause the end with the arrow to go down!

How air pressure affects the barometer


Making an experiment out of the barometer

Use a ruler

Make yourself a little log book where you can make note of the barometric pressure a couple of times a day for a few days. And you should also note the weather.

After a little bit of observation you will be able to see how the pressure changes before a storm moves in! Then you will be able to make predictions about a storm coming as the pressure changes!






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