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Centrifugal pump similarity: discharge vs. rotational speed How does the discharge Q of a centrifugal pump vary with impeller rotational speed N (all else equal)? Choose the correct relation.

Q: Centrifugal pump similarity: discharge vs. rotational speed How does the discharge Q of a centrifugal pump vary with impeller rotational speed N (all else equal)? Choose the correct relation.

Concept For a given geometry and diameter, the flow (via Vf) scales with tip speed ∝ N, so Q ∝ area × Vf ∝ N. Affinity law With constant diameter: Q ∝ N; Head H ∝ N²; Power P ∝ N³. Final Answer Q ∝ N

Difficulty: Easy

Q ∝ N
Q ∝ 1/N
Q ∝ N²
Q ∝ 1/N²

Correct Answer: Q ∝ N

Explanation:

Concept
For a given geometry and diameter, the flow (via V_f) scales with tip speed ∝ N, so Q ∝ area × V_f ∝ N.

Affinity law
With constant diameter: Q ∝ N; Head H ∝ N²; Power P ∝ N³.

Final Answer
Q ∝ N

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