# Hydraulic Machines Questions and Answers – Derivation of Specific Speed

This set of Hydraulic Machines Quiz focuses on “Derivation of Specific Speed”.

1. Specific speed is denoted by ________
a) N
b) n
c) Ns
d) S

Explanation: Specific speed is denoted by Ns. It is used to characterize speeds in turbo machinery. Some of the main examples of turbomachinery are turbines. Specific speed plays an important role in the turbine.

2. Specific speeds are used in pumps to determine ________
a) Temperature
b) Reaction speed
c) Suction specific speed
d) Wheel speed

Explanation: Specific speeds are used in pumps to determine. Specific speed is denoted by Ns. It is used to characterize speeds in turbo machinery. Some of the main examples of turbomachinery are turbines. Specific speed plays an important role in the turbine.

3. The tube at the exit of the nozzle increases the _______
a) Temperature
b) Pressure
c) Volume of the flow
d) Density of flow

Explanation: The draft tube at the exit of the nozzle increases the pressure in the fluid. It increases it at the expense of its velocity. This means that the turbine can reduce its pressure without fear of back flow to the tail race.

4. Specific speed is used to characterize _______
a) Turbomachinery speed
b) Flow speed
c) Energy flow
d) Heat generated

Explanation: Specific speed is used to characterize Turbomachinery speed. Specific speed is denoted by Ns. It is used to characterize speeds in turbo machinery. Some of the main examples of turbomachinery are turbines. Specific speed plays an important role in the turbine.

5. Specific speed predicts the shape of a/an _________
a) Pump
c) Impeller
d) Motor

Explanation: Specific speed predicts the shape of an impeller. Some of the main examples of turbomachinery are turbines. Specific speed plays an important role in the turbine.
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6. What helps in categorizing the impellers?
a) Quasi static number
b) Rotor
c) Height of draft tube
d) Pump

Explanation: The impellers are categorized using a quasi static non dimensional number. It helps in determining the impellers time and proportional quantities.

7. Imperial units is defined as _________
a) Temperature by pressure
b) Tail race and head race
c) Revolutions per minute
d) Turbine performance

Explanation: In Imperial units it is defined as the speed in revolutions per minute at which a geometrically similar impeller would operate if it were of such a size as to deliver one gallon per minute against one foot of hydraulic head.

8. Ratio of pump or turbine with reference pump or turbine is called as _________
a) Efficiency
b) Performance
c) Heat generated
d) Relative velocity

Explanation: Ratio of pump or turbine with reference pump or turbine is called as the performance of that particular turbine or pump.

9. Low specific speed in hydraulic head is developed due to _________
a) Mass flow rate
b) Increase in temperature
c) Centrifugal force
d) Increase in pressure

Explanation: Low specific speed with a radial flow in impellers are developed in hydraulic head principally due to centrifugal force. Pumps having higher specific speed develop a head that is partly by axial force.

10. Centrifugal pump impellers have speed ranging from ________
a) 500- 10000
b) 50- 100
c) 200-300
d) 0-50

Explanation: Centrifugal pump impellers have speed ranging from 500- 10000 English units. IT has got radial flow with pumps mixed with axial flow pumps.

11. What is the unit of specific speed in metric system?
a) m.s
b) m/s
c) m3/s
d) m

Explanation: The unit of specific speed in the metric system is given as m3/s. Specific speed is denoted by Ns. It is used to characterize speeds in turbo machinery.

12. Specific speed develop a hydraulic flow through the centrifugal pumps.
a) True
b) False

Explanation: Specific speed develop a hydraulic flow through the centrifugal pumps. Specific speed is denoted by Ns. It is used to characterize speeds in turbo machinery. With the increase in specific speeds, diameter of the impellers increases.

13. Net suction speed is used in problems with cavitation.
a) True
b) False

Explanation: Net suction speed is used in problems with cavitation during the pump’s operation on the suction side. It is defined by centrifugal and axial pump.

14. Low specific speed in hydraulic head is developed due to _________
a) Mass flow rate
b) Increase in temperature
c) Centrifugal force
d) Increase in pressure

Explanation: Low specific speed with a radial flow in impellers are developed in hydraulic head principally due to centrifugal force. Pumps having higher specific speed develop a head that is partly by axial force.

15. The runner diameter in a turbine is denoted as __________
a) A
b) Dr
c) Rr
d) De

Explanation: The runner diameter in a turbine is denoted as ‘De’. Its SI unit is meters. It plays an essential role in improving the efficiency of the turbine. As the efficiency of the turbine is related to its design and structure.

Sanfoundry Global Education & Learning Series – Hydraulic Machines.

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