What primarily distinguishes a rotary pump from a centrifugal pump?

A rotary pump is primarily distinguished from a centrifugal pump by its use of mechanical means to move fluid. In rotary pumps, fluid is displaced through the action of rotating components, such as gears, lobes, or screws. This mechanism creates a pressure differential, drawing fluid into the pump and pushing it out efficiently.

Centrifugal pumps operate by converting kinetic energy from a rotating impeller into hydraulic energy; they rely on the movement of the liquid to create flow, rather than direct mechanical displacement. While they do create pressure, it's through the centrifugal force generated by the rotation of the impeller, which acts on the fluid, propelling it outward. This key difference emphasizes that the rotary pump's operation is more about mechanical engagement rather than the kinetic energy principles primarily applied in centrifugal pump designs.

The option regarding centrifugal pumps not using kinetic energy is incorrect because they fundamentally operate through kinetic energy, transforming it to create pressure and flow. Similarly, the statement about rotary pumps relying on kinetic energy contradicts the fundamental operating principles of rotary pumps, which focus on mechanical movement. The assertion about centrifugal pumps being used only for heavier liquids is misleading, as centrifugal pumps can handle a broad range of fluids, including lighter ones, not limited to just heavier liquids.