Which of the following is an example of a positive displacement pump?

A positive displacement pump works by trapping a fixed amount of fluid and then forcing that volume into the discharge pipe. The reciprocating design is a classic example of this operation, as it uses a piston that moves back and forth within a cylinder. As the piston moves in one direction, it creates a vacuum that draws fluid into the chamber. When the piston moves in the opposite direction, it compresses that volume of fluid and pushes it out through the discharge.

The characteristic that makes the reciprocating pump a positive displacement pump is its ability to maintain consistent flow regardless of downstream pressure changes. This is particularly useful in applications requiring precise flow rates and high pressures.

Other types of pumps listed, such as jet, centrifugal, and propeller pumps, operate on fundamentally different principles. Jet pumps utilize the Venturi effect which involves pressure changes and the movement of fluid through nozzles rather than displacing a fixed volume. Centrifugal pumps rely on rotational energy and kinetic energy to move fluid, which means their flow can vary with changes in pressure. Propeller pumps function by moving water with the blades of a propeller in a manner similar to a boat's propulsion system, but they do not trap and displace fixed volumes of fluid like a positive displacement pump does