Centrifugal pumps use one or more impellers, which attach to and rotate with the pump shaft. This provides the energy that moves liquid through the pump and pressurizes the liquid to move it through the piping system. The pump therefore converts mechanical energy from a motor to energy of a moving fluid. A portion of the energy goes into kinetic energy of the fluid motion, and some goes into potential energy, represented by fluid pressure or by lifting the fluid, against gravity, to a higher altitude.