When you plug the vacuum cleaner into the outlet and turn it on, the following happens:
1. First of all, the electric current will operate the motor, which is attached to the fan, which resembles an airplane propeller.
2. As the blades begin to turn, they will force the air upwards, towards the exhaust port.
3. When the air particles are driven forwards, the density of the particles will increase in front of the fan and therefore decrease behind it.
The pressure drop that occurs behind the fan is similar to the pressure drop when you take a drink through a straw. The pressure level in the area that is behind the fan will drop below the pressure level that is outside of the vacuum cleaner.
This will create a suction inside of the vacuum cleaner. The ambient air will push itself into the vacuum cleaner through the intake port because the air pressure that is inside of the vacuum cleaner is much lower than the pressure on the outside.
Picking the dirt up
The stream of air that the vacuum generates is just like a stream of water. The air particles that move will rub against any loose dust or debris and if it is light enough, the friction will carry the material around the inside of the vacuum cleaner.
As the dirt continues on to the exhaust port, it will pass through the cleaner bag. They tiny holes in the vacuum cleaner bag are large enough to let the air pass through, although too small for the dust particles to fit through. Therefore, when the air current gets into the bag, the dirt and debris will be collected there.
You can stick the bag anywhere along the path between the intake tube and the exhaust port, just as long as the air current passes through.
Suction
The power of a vacuum cleaner's suction will depend on several factors. The suction can be stronger or weaker depending on:
1. Fan power - In order to generate a strong suction, the motor needs to turn at a good speed.
2. Air passageway - When a lot of debris builds up in the bag, the air will face a greater level of resistance on the way out. Each particle of air will move slowly due to the increase in drag. This is the reason why a vacuum cleaner works much better once you've replaced the bag than when you have been using it for a while.
3. Size of the intake port - With the speed of the vacuum fan being constant, the amount of air that passes through the vacuum cleaner per second is also constant.
