Question Bank • QB_SUB_IDE_0244 MCQ • 1 Mark

Section 5: Irrigation and Drainage Engineering

Centrifugal Pumps: Performance Curves & Affinity Laws

Subtopic: Affinity law discharge scaling with speed

Question Statement:

The dimensionless or dimensional specific speed of a pump ($N_s = \frac{N \sqrt{Q}}{H^{3/4}}$) serves primarily as:

Options:

  • (A) A shape and geometric parameter for classifying impellers (radial, mixed, or axial flow)
  • (B) A measure of electric motor efficiency
  • (C) The RPM at which cavitation commences
  • (D) The critical diameter of the suction pipe

Answer Key:

A

Step-by-Step Solution & Explanation

Specific speed characterizes impeller geometry: low $N_s$ indicates radial flow, medium indicates mixed flow, and high $N_s$ indicates axial flow.
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