Question

In which of the following pumps, the displacement of fluid is by rotating action

• A. Centrifugal pump
• B. Gear pump
• C. Plunger pump
• D. Piston pump

Hint:

Gear pumps are positive displacement pumps where rotating gears directly displace fluid, unlike centrifugal pumps which use rotation to impart kinetic energy.

Answer 1

The Correct Option is B

Step 1: Understand the mechanism of fluid displacement in pumps. 
The question asks for a pump where fluid displacement occurs by a rotating action. Let’s analyze the mechanism of each type of pump:
Centrifugal pump: This pump uses a rotating impeller to impart kinetic energy to the fluid, creating a centrifugal force that moves the fluid outward. While the impeller rotates, the primary action is the conversion of kinetic energy to pressure, not direct displacement by rotation.
Gear pump: This is a positive displacement pump where two meshing gears rotate to trap fluid in the spaces between the gear teeth and the pump casing, then displace it to the outlet. The fluid displacement is directly caused by the rotating action of the gears.
Plunger pump: This is a reciprocating pump where a plunger moves back and forth to displace fluid. The motion is linear (reciprocating), not rotating.
Piston pump: This is also a reciprocating pump where a piston moves linearly to displace fluid, similar to a plunger pump, without rotating action.
Step 2: Identify the pump with rotating action for displacement. 
Gear pumps directly displace fluid through the rotation of gears, making them a clear example of displacement by rotating action.
Centrifugal pumps involve rotation, but the displacement is due to centrifugal force and velocity increase, not direct displacement by the rotation itself.
Plunger and piston pumps use linear motion, not rotation. 
Step 3: Evaluate the options. 
(1) Centrifugal pump: Incorrect, as the primary mechanism is centrifugal force from rotation, not direct displacement by rotating action. Incorrect.
(2) Gear pump: Correct, as the rotating gears directly displace fluid in a positive displacement manner. Correct.
(3) Plunger pump: Incorrect, as it uses reciprocating (linear) motion, not rotation. Incorrect.
(4) Piston pump: Incorrect, as it also uses reciprocating motion, not rotation. Incorrect.
Step 4: Select the correct answer. 
The pump where the displacement of fluid is by rotating action is the gear pump, matching option (2).