A _______ pump is a positive displacement pump.

• A. Centrifugal
• B. Jet
• C. Reciprocating
• D. Diaphragm

Answer: (C)

Positive displacement pumps move a fixed amount of fluid with each cycle. The mechanism traps a specific volume and then pushes it out, so the flow rate is tied to how fast the cycles run, not to the system pressure. A reciprocating pump does this by using a piston or plunger that moves back and forth, capturing a precise volume on each stroke and delivering that same volume on the discharge stroke. That fixed-volume per cycle behavior is the defining feature of a positive displacement pump, which is why this option fits best.

Centrifugal and jet pumps rely on imparting velocity to the fluid with impellers or jet effects; their output depends on head and system conditions and they don’t deliver a fixed per-stroke volume. A diaphragm pump also displaces a fixed amount per cycle by flexing a membrane, but the classic, most direct example used in many contexts is the reciprocating mechanism.