Generally driven by a motor, a “centrifuge” puts an object in rotation around a fixed axis by application of a perpendicular force to the axis. The sedimentation principle is used here, and the centripetal acceleration separates substances of greater and lesser density.

The theory behind the centrifuge is fairly straight-forward. Rather than specifying a rotational speed such as revolutions per minute, the amount of acceleration to be applied to a sample is the typical protocol for centrifugation. As the product of the radius and the square of the angular velocity, acceleration is often quoted in multiples of “g”, the standard acceleration of gravity at the Earth's surface.

Samples in a centrifuge will generally be subject to different accelerations since two rotors with different diameters run at the same rotational speed. Applications are seen in chemistry, biology, and biochemistry where isolation and separation of suspensions is common. The Centrifuges here vary widely in speed and capacity and usually comprise a rotor containing two or more numbered wells, inside which samples may be placed.

Other variants, the first being the Zippe-type centrifuge developed in the former Soviet Union, can be used for separation of isotopes for use in nuclear power and weapon programs.

A centrifuge used in uranium enrichment is of the Gas type. Uranium-238 from the uranium hexafluoride gas will tend to concentrate at the walls of the centrifuge when it spins, while the Uranium-235 isotope gets extracted and concentrated using a scoop placed selectively within the centrifuge. Many thousands of centrifuges are required for enriching enough uranium for use in nuclear reactors, atomic bombs etc.

There are certain exceptionally large centrifuges which help in testing the reactions and tolerance levels of pilots and astronauts at speeds above those experienced in Earth's normal gravity. These “Human Centrifuges” simulate a feeling of gravity and have been proposed for future long-duration space missions. The simulated gravity would prevent or, at the least, reduce bone decalcification and muscle atrophy which commonly affects astronauts.