How a Vacuum Cleaner Works

When you sip a drink through a straw, you are utilising the simplest of all suction mechanisms. Sucking the drink causes a pressure drop between the bottom of the straw and the top of the straw. With greater fluid pressure at the bottom than the top, the drink is pushed up to your mouth. ­

The same basic mechanism is at work in a vacuum cleaner, although the execution is a bit more complicated.

Let’s look inside a vacuum cleaner to find out how it puts suction to work when cleaning up dust and debris.

Vacuum cleaner

As can be seen, the standard vacuum cleaner design is very simple, but it relies on a host of physical principles to clean effectively.

It may look like a complicated machine, but the conventional vacuum cleaner is actually made up of only six essential components:

  • An intake port, which may include a variety of cleaning accessories
  • An exhaust port
  • An electric motor
  • A fan
  • A porous bag
  • A housing that contains all the other components

When you plug the vacuum cleaner in and turn it on, this is what happens:

  1. The electric current operates the motor. The motor is attached to the fan, which has angled blades (like a planes propeller).
  2. As the fan blades turn, they force air forward/upwards, towards the exhaust port and via the dust bag where dust and debris will be retained.
  3. When air particles are driven forward, the density of particles (and therefore the air pressure) increases in front of the fan and decreases behind the fan.

This pressure drop behind the fan is just like the pressure drop in the straw when you sip from your drink. The pressure level in the area behind the fan drops below the pressure level outside the vacuum cleaner leaving an area of low air pressure below the fan, and near the floor (this is the ambient air pressure).

This creates suction, essentially a partial vacuum, inside the vacuum cleaner. The ambient air pushes itself into the vacuum cleaner through the intake port because the air pressure inside the vacuum cleaner is lower than the pressure outside, as air always moves from areas of high pressure to comparatively low pressure. This is the process that will remove dirt from the floor.

Because the fan has created an area of low pressure near the floor, air from the floor is going to move in to fill that space, due to how air pressure works. Sometimes, very small particles of dirt and dust will be lifted by the low pressure area as well. In addition to this, air takes larger, loose particles of dust and dirt with it using friction.

As long as the fan is running and the passageway through the vacuum cleaner remains open, e.g. no kinks in the hose, no blockages etc, there is a constant stream of air moving through the intake port and out the exhaust port.

Many vacuum cleaners, in addition to using a fan, also use a rotating brush that sweeps the floor. Sometimes, this rotating brush is powered by the same motor that runs the vacuum cleaners fan, although many commercial specification vacuum cleaners such as the Sebo BS36 Comfort, will have twin motors, one to power the fan and the other to power the brush.

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Occasionally, this brush will be powered by being pushed back and forth across the floor instead. Either way, this brush serves the purpose of loosening trapped dirt and dust particles stuck in the carpet that would not have been picked up by the air pressure, and moving them to the surface, or even into the air, where they will be picked up easily.

Once the vacuum cleaner has sucked in air and dirt particles, the high pressure area directly above the fan — remember, air travels from comparatively high to low pressure areas — causes them to continue to move upwards. At this point, the air and dirt particles enter the vacuum cleaners porous bag. This bag is porous enough to allow air to pass through easily, but dense enough to trap dirt, dust and any other larger particles that were on the floor. After exiting the bag, the air leaves the back of the vacuum cleaner, passing through an exhaust filter, leaving any dirt that came with it trapped in the bag.

Repeated applications of a rotating brush tend to loosen all dirt after a while, as well as trapping larger particles completely in the bristles and lifting them where they can be more easily sucked up into the vacuum cleaners porous bag.

With the simple principles described above, floors are kept cleaner.