# Hydraulic Machines Questions and Answers – Main Characteristic Curves

This set of Hydraulic Machines Multiple Choice Questions & Answers (MCQs) focuses on “Main Characteristic Curves”.

1. The characteristic curves of a centrifugal pump, plots ______ required by the pump.
a) Velocity
b) Pressure
c) NPSH
d) Velocity and pressure

Explanation: The characteristic curves of a centrifugal pump, plots net positive suction head required by the pump. These curves play an important role in determining the efficiency of a centrifugal pump.

2. What is the shape of the diffuser in the centrifugal pump?
a) Round
b) Dough nut
c) Rectangle
d) Cylindrical

Explanation: The shape of the diffuser passing present in the centrifugal pump is doughnut shaped. It is made into that shape as it allows the device to scroll up and down. Due to this, the casing decelerates the flow.

3. When the casing in a centrifugal pump decelerates the flow, what increases?
a) Pressure
b) Temperature
c) Volume
d) Flow rate

Explanation: When the casing in a centrifugal pump decelerates the flow, pressure in the turbine increases. The diffuser helps this happen. The shape of the diffuser passing present in the centrifugal pump is doughnut shaped.

4. Which among the following is not a characteristic curve for centrifugal pump?
a) Transfer speed vs Transfer pressure
c) Power input vs pump efficiency
d) Specific speed vs pump efficiency

Explanation: The primary objective of a centrifugal pump is to transfer energy. Centrifugal pump is a turbomachinery. Transfer speed vs Transfer pressure is not considered as a correct characteristic curve.

5. The consequence of Newtons second law is _________
a) Conservation of angular momentum
b) Conservation of mass
c) Conservation of potential energy
d) Conservation of kinetic energy

Explanation: The consequence of Newtons second law is the conservation of angular momentum. This, in accordance with newtons second law, provides the basic details to define parameters in the centrifugal pump.
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6. Which of the following is taken into account during a characteristic curve?
a) Flow rate
b) Cavitation
c) Tolerances
d) Casing

Explanation: Flow rate is an important parameter that is taken into account for a characteristic curve. These curves play an important role in determining the efficiency of a centrifugal pump.

7. The normal operating range of centrifugal pump is sufficient to plot the characteristic curve.
a) True
b) False

Explanation: The normal operating range of centrifugal pump is sufficient to plot the characteristic curve. Centrifugal pumps are used to transport fluids. They transport fluids by conversion of energies.

8. The inlet passage of water entry is controlled by ________
b) Gate
c) Tail race
d) Pump

Explanation: The inlet passage of water entry is controlled by the gate opening. The gate opening is an opening that sends only a percentage of fluid through the inlet passages for water to enter to the turbine.

9. As the specific speed increases, the slope of HQ curve _______
a) Decreases
b) Increases
c) Independent
d) Remains the same

Explanation: As the specific speed increases, the slope of HQ curve increases. It becomes steeper with the corresponding increase in the specific speed.

10. The primary selection tool is called as _______
a) Pump curve
b) Speed curve
c) Power curve
d) Fluid curve

Explanation: The primary selection tool is called as pump curve. It plays an essential role in determining efficiency.

11. In case of centrifugal turbines with low specific speed, the efficiency curve is _________
a) Pointed
b) Small
c) Steep
d) Flat

Explanation: In case of centrifugal turbines with low specific speed, the efficiency curve is relatively flat in the vertex. These curves play an essential role in determining the overall performance of the turbine.

12. In case of centrifugal turbines with high specific speed, the efficiency curve is
a) Pointed
b) Small
c) Steep
d) Flat

Explanation: In case of centrifugal turbines with high specific speed, the efficiency curve is relatively pointed in the vertex. These curves play an essential role in determining the overall performance of the turbine.

13. With the increase in the input power, efficiency _______
a) Increases
b) Decreases
c) Same
d) Independent

Explanation: With the increase in the input power, efficiency decreases. As the input power is inversely proportional to the efficiency of the pump.

14. What is unit of standard acceleration?
a) kg/m
b) kg/s
c) kg/m3
d) N/m

Explanation: The unit of standard acceleration of the centrifugal pump is kg/m3. It is denoted as g. It is also called as the acceleration due to gravity. Thus, the correct option is ‘c’.

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