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Centrifugal pump similarity: discharge vs. impeller diameter For a given speed and inlet width, how does discharge Q vary with impeller diameter D in a centrifugal pump? Choose the correct dependence.

Difficulty: Easy

Directly proportional to D
Inversely proportional to D
Directly proportional to D²
Inversely proportional to D²

Correct Answer: Directly proportional to D

Explanation:

Concept
At inlet, Q = π D b V_f. For fixed b and similar V_f (same N), Q scales with D.

Notes
Under full similarity (b ∝ D and V_f ∝ D N), Q would scale as D³ N, but with b and N fixed as in many textbook MCQs, the direct proportionality to D is appropriate.

Final Answer
Directly proportional to D

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