City Guilds Model Questions Vol1 2021 Engineering Question 1

Practice objective / multiple choice question 1 from the 2021 City Guilds Model Questions Vol1 Engineering examination.

City Guilds Model Questions Vol1 2021 Engineering Objective / Multiple Choice Hard Difficulty
Question 1 CITY_GUILDS_MODEL_QUESTIONS_VOL1 • 2021 • ENGINEERING • objective

A centrifugal pump has a head‑flow characteristic given by \(H = 70 - 0.02 Q^{2}\) where \(H\) is in metres and \(Q\) is the flow rate in litres per second. The pump is driven by a 5 kW electric motor whose efficiency is \(85\%\). The pump efficiency is assumed to be \(70\%\). Determine the maximum flow rate that can be delivered without exceeding the motor's rated power. Then state whether a required flow of 150 L min⁻¹ at a total head of 30 m can be achieved, and identify which component (pump or motor) limits the system.

Answer Options

Correct Answer A. Maximum flow ≈ 4.35 L s⁻¹ (≈261 L min⁻¹); the required 150 L min⁻¹ is achievable, and the motor power is the limiting factor.
B. Maximum flow ≈ 3.80 L s⁻¹ (≈228 L min⁻¹); the required 150 L min⁻¹ is achievable, and the pump efficiency is the limiting factor.
C. Maximum flow ≈ 5.10 L s⁻¹ (≈306 L min⁻¹); the required 150 L min⁻¹ cannot be achieved, and the motor power is the limiting factor.
D. Maximum flow ≈ 4.35 L s⁻¹ (≈261 L min⁻¹); the required 150 L min⁻¹ is achievable, and the pump is the limiting component.
Correct Answer
A
Correct Option:
Maximum flow ≈ 4.35 L s⁻¹ (≈261 L min⁻¹); the required 150 L min⁻¹ is achievable, and the motor power is the limiting factor.

About This Question

This is City Guilds Model Questions Vol1 2021 Engineering Question 1. It is one of the objective questions from the 2021 City Guilds Model Questions Vol1 Engineering examination.

Difficulty level: Hard .

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