The power of a vacuum cleaner motor is one of the most misrepresented and misunderstood aspects of vacuum cleaner technology. This confusion has been accentuated by many manufacturers and salespersons in their attempt to make their products appear superior to others. At times this takes the form of performing amazing demonstrations of the vacuum cleaner's abilities. Often, when analyzed with a few basic laws of physics in mind, these amazing feats prove very little and are relatively meaningless!
The laws of physics behind this feat are rather simple. As explained in our article on the Fan or Impeller, a partial vacuum (area of reduced air pressure) is produced by the spinning fan. The difference in pressure between the normal atmospheric pressure and the reduced air pressure in the fan is what normally causes air to flow toward the fan. As air flow is restricted, the air pressure within the vacuum cleaner, hose, etc. drops closer to the pressure that is at the fan. It is the force exerted by this difference between normal and reduced air pressure which picks up the steel balls. This force is proportional to the area upon which it is applied as described below.
The unit of measurement for pressure is often stated as force per area as in "pounds per square inch", etc. An alternate expression of pressure or pressure difference is to state how high in a tube a liquid of known weight is pushed or pulled. Examples of this are the barometer (calibrated in millimeters of mercury or millibars of pressure) for measuring atmospheric pressure and the sealed suction gauge (calibrated in inches of water lift) for measuring the suction (difference in air pressure mentioned above) of a vacuum cleaner.
One cubic inch of water weighs 0.036 pounds so the pressure difference for a vacuum cleaner which measures 100" of water lift on a suction gauge is 3.6 pounds per square inch. A bit of math shows us that a vacuum cleaner with only 30" of water lift would exert about 1 pound per square inch on a steel ball. The steel balls are aproximately 1" in diameter, giving about 0.78 square inches of cross sectional area so the force exerted to pick up a 3 ounce steel ball is about 12 ounces. While canister type vacuum cleaners measure from 60 to 103 inches of water lift, some upright types with on-board attachments only measure 30 to 60 inches of water lift. Since the force exerted is proportional to the area, even more impressive demonstrations can be done as explained in our article titled "So Powerful that it can Lift an Adult Person." As you can see, it really isn't such a marvel that an upright can pick up steel balls. To learn about various methods for rating vacuum cleaner motors, see our article about the Power of the Suction Motor.
There are many important performance aspects of a vacuum cleaner system which you can read about in our article on Identifying Good Performance Factors. These include the Power of the Suction Motor, Effects of Brushing Action, effect of internal resistance on the Air Flow through the System, as well as the Efficiency of Paper Bags and Filtration Efficiency - HEPA, Micron, etc.
To choose a durable vacuum cleaner which will meet your cleaning tasks and preferences, see our articles on Identifying Durable Designs & Construction and Match Your Tasks and Cleaning Style. A good, knowledgeable sales person like those at Ristenbatt Vacuum Cleaner Service can help you determine which vacuum cleaner system will be the best for you in your particular cleaning situation.
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