Which component of a centrifugal pump moves in the water?

• A. Cylinder
• B. Impeller
• C. Shaft
• D. Valve

Answer: (B)

In a centrifugal pump, the component that actually moves and energizes the liquid is the impeller. Its rotating blades grab water at the eye and push it outward as the impeller spins, transferring energy to the fluid and increasing its velocity and pressure as it flows toward the discharge. The shaft simply transmits the motor’s torque to the impeller; it doesn’t itself move water. A valve controls flow, not energy transfer, and a cylinder isn’t the active pumping element in this type of pump.