Originally, carpets and rugs were cleaned by lifting them, taking them outside, hanging them over a line and beating them with a carpet beater (a very dusty job), or by using a stiff brush and dustpan. Vacuum cleaners have made cleaning carpets so much quicker and easier by sucking the dirt and dust from the carpet and depositing it in a filter bag or dust collection tank.
Making a Vacuum Cleaner
This won’t be something to clean an entire floor with, but shows how vacuum cleaners work. Cut off the bottom third of a two litre soft drinks bottle, and make a slit down the side of the bottom part, so that it will slide inside the top part. Securely nail a dowel or tape a strip of folded paper to the bottom part to make a handle. The bottom part of the bottle is the piston and the top half of the bottle is the cylinder of the vacuum cleaner.
Cut a hole near the top of the bottle, about 2 cm across and about 4 cm below the neck. Make a bag from tissue paper – fold a piece about 10 cm by 15 cm in half and tape up the sides, all the way round, not leaving any gaps. Tape the bag to the hole in the neck – this is the filter bag for the vacuum cleaner.
Glue or tape a piece of thread or fine string to a ping pong ball, drop the ball inside the top half of the bottle, and thread the string through the neck of the bottle. Tape the other end of the thread to the outside – the ball should hang just inside the neck. This is the valve.
How Does The Vacuum Cleaner Work?
Push the piston (bottom piece of the bottle) inside the cylinder (top piece of the bottle) as far as it will go. Drop a few very small pieces of screwed up paper on the floor, put the neck of the ‘vacuum cleaner’ over them, and pull the piston almost all the way out – the air can now fill a bigger space and so the air pressure drops inside the cylinder. The air outside is at higher pressure than the air inside, so it rushes in. This should pull the tissue paper in with it.
Push the piston back in – the valve (ping pong ball) should block the neck of the bottle. This compresses the air inside and increases the air pressure. As the pressure is lower outside the cylinder, the high pressure air wants to rush out, and the only exit is through the tissue paper, pushing the paper scraps into the filter bag.
In a ‘real’ vacuum cleaner, a fan makes the air move quickly. This reduces the air pressure inside the vacuum cleaner, and air from outside, where the pressure is higher, rushes in, carrying the dirt from the carpet with it.
Some Things to Try
Try pulling and pushing the piston of the drinks bottle vacuum cleaner quickly or slowly. Which is better at sucking up the paper scraps, and which is better at getting them in the bag? How could the vacuum cleaner work more efficiently?