How Vacuum Cleaners Work

While the vacuum may appear to be a complicated machine, it is actually made up of only six components: intake port, exhaust port, electric motor, fan, porous bag, and the housing that stores all components.

When the unit is plugged into an outlet and turned on the following happens:

1. The electric current operates the motor, which is attached to a fan that looks like an airplane propeller.
2. As the fan blades turn they force air upwards, towards the exhaust port.
3. When the air is driven forward, the density of the air particles increases in front of the fan and decreases behind the fan.

The drop in pressure behind the fan is similar to the pressure drop that occurs when sucking through a straw.  The pressure level in that area behind the fan drops below the level that is outside the unit.

This creates a suction inside of the unit.  The air pushes itself into the unit through the intake port because the air pressure inside the unit is much lower than the pressure outside.

Picking the dirt up

The stream of air that the unit generates is much like a stream of water.  The air particles that move rub against loose dust and debris and if it is light enough the friction will carry the material around inside the unit.

As the dirt continues to the exhaust port it passes through the cleaner bag.  The holes in the bag are large enough to let air pass through, but too small for dust particles to fit through.  When the air current gets into the bag, the dirt and debris is collected there while the air is released.

The bag can be found anywhere along the path between the intake tube and the exhaust port as long as the air current passes through.

Suction

The vacuum cleaner's suction will depend on a few factors and can be stronger or weaker depending on:

1. Fan power - To generate a strong suction, the motor must turn at an adequate speed.
2. Air passageway - When excess debris builds up in the bag the air faces greater resistance on the way out.  Each particle will move more slowly due to the increase in drag.  This is why the unit works much more efficiently when the bag has been replaced.
3. Size of the intake port - Since the speed of the fan is constant, the amount of air that passes through the unit per second is also constant.