Making a Barometer

Video Transcript

"Hi, I'm Steve Jones, and I'm going to tell you how to make a barometer. Now, a barometer is something that measures atmospheric pressure, so we're only measuring atmospheric pressure. And to measure atmospheric pressure there are basically two different types of device. The first is this traditional barometer, a mercury barometer. In it is a liquid, and the liquid is usually mercury, and this whole thing contains mercury. Now, apart from this being a very poisonous substance it's not a very nice material to work with, and it is quite unpleasant. It's also very heavy, a liquid metal. Atmospheric pressure pushes down on here and it creates a column of mercury. This is, this tubs is filled right to the top at first, and when you raise it up you get this vacuum in the top, so that is a direct measurement in centimeters of mercury or meters of mercury, the atmospheric pressure. Normal atmospheric pressure is about seventy six centimeters. Now, that would be all right if mercury weren't such an unpleasant material. If you do the same thing with water which might have its advantages, unfortunately, it would have to be ten meters high which is a bit impractical, so as a device for making at home it's probably not the best one to try. The aneroid type barometer relies on having a sealed container on which there is a pointer attached, and as atmospheric pressure increases the container is compressed and this pointer moves. Now, if the pivot; this is a fixed pivot. If this fixed pivot is quite close to here then you will get a big movement at this end for a small movement at this end. And this is a traditional type of aneroid barometer. This is the type you could make at home. All you need is something which will be crushed by the atmospheric pressure. Fix it, and fix the pointer very close to the pivot on the side of the container; maybe a plastic bottle of some kind, and that pointer will move up a scale when the pressure increases. When the pressure decreases it'll move down the scale. You can find a normal atmospheric pressure. You have to look at the weather forecast and mark on your zero. This is a simple aneroid type barometer; one that you can make at home. So, that is basically the kinds of barometers that there are, and how to make one at home."