140+ Hydraulics Machines Solved MCQs

1.

A Pelton wheel is

A. tangential flow impulse turbine
B. inward flow impulse turbine
C. outward flow impulse turbine
D. inward flow reaction turbine
Answer» A. tangential flow impulse turbine
2.

Which of the following statement is correct?

A. The centrifugal pump is suitable for large discharge and smaller heads
B. The centrifugal pump required less floor area and simple foundation as compared to reciprocating pump
C. The efficiency of centrifugal pump is less as compared to reciprocating pump.
D. all of the above
Answer» D. all of the above
3.

The runaway speed of a hydraulic turbine is the speed

A. at full load
B. at which there will be no damage to the runner
C. corresponding to maximum overload permissible
D. at which the turbine will run freely without load
Answer» D. at which the turbine will run freely without load
4.

In an impulse turbine, the jet of water impinges on the bucket with a low velocity and after flowing over the vanes, leaves with a high velocity.

A. True
B. False
Answer» B. False
5.

The gross or total head of the turbine is the

A. sum
B. difference
C. product
Answer» B. difference
6.

The specific speed of a centrifugal pump, delivering 750 litres of water per second against a head of 15 metres at 725 r.p.m., is

A. 24.8 r.p.m.
B. 48.2 r.p.m.
C. 82.4 r.p.m.
D. 248 r.p.m.
Answer» C. 82.4 r.p.m.
7.

In a reciprocating pump, air vessels are used to

A. smoothen the flow
B. reduce suction head
C. increase delivery head
D. reduce acceleration head
Answer» D. reduce acceleration head
8.

The capacity of a hydraulic accomulator is generally specified as the maximum amount of energy stored.

A. True
B. False
Answer» A. True
9.

A Pelton wheel develops 1750 kW under a head of 100 metres while running at 200 r.p.m. and discharging 2500 litres of water per second. The unit power of the wheel is

A. 0.25 kW
B. 0.75 kW
C. 1.75 kW
D. 3.75 kW
Answer» C. 1.75 kW
10.

In a reaction turbine, the pressure head of water, while flowing over the vanes, is converted into kinetic head before leaving the wheel.

A. Agree
B. Disagree
Answer» B. Disagree
11.

A turbine is required to develop 1500 kW at 300 r.p.m. under a head of 150 m. Which of the following turbine should be used?

A. Pelton wheel with one nozzle
B. Pelton wheel with two or more nozzles
C. Kaplan turbine
D. Francis turbine
Answer» A. Pelton wheel with one nozzle
12.

A Kaplan turbine is an axial flow reaction turbine.

A. Correct
B. Incorrect
Answer» A. Correct
13.

The action of a centrifugal pump is that of a reversed reaction turbine.

A. Correct
B. Incorrect
Answer» A. Correct
14.

Geometric similarity is said to exist between the model and the prototype, if both of them

A. have identical velocities
B. are equal in size and shape
C. are identical in shape, but differ only in size
D. have identical forces
Answer» C. are identical in shape, but differ only in size
15.

A Pelton wheel working under a constant head and discharge, has maximum efficiency when the speed ratio is

A. 0.26
B. 0.36
C. 0.46
D. 0.56
Answer» C. 0.46
16.

Delivery head of water of a centrifugal pump is inversely proportional to diameter of its impeller.

A. Yes
B. No
Answer» B. No
17.

The efficiency of a reaction turbine for a given head

A. decreases
B. increases
Answer» A. decreases
18.

The undershot water wheels are those in which

A. the wheel runs entirely by the weight of water
B. the wheel runs entirely by the impulse of water
C. the wheel runs partly by the weight of water and partly by the impulse of water
D. none of the above
Answer» B. the wheel runs entirely by the impulse of water
19.

In the casing of a centrifugal pump, the kinetic energy of the water is converted into pressure energy before the water leaves the casing.

A. True
B. False
Answer» A. True
20.

Head developed by a centrifugal pump is

A. proportional to diameter of impeller
B. proportional to speed of impeller
C. proportional to diameter and speed of impeller
D. none of the above
Answer» C. proportional to diameter and speed of impeller
21.

The ratio of quantity of liquid discharged per second from the pump to the quantity of liquid passing per second through the impeller is known as

A. manometric efficiency
B. mechanical efficiency
C. overall efficiency
D. volumetric efficiency
Answer» D. volumetric efficiency
22.

The efficiency of a Pelton wheel working under constant head

A. remains same
B. increases
C. decreases
Answer» B. increases
23.

The cavitation in ahydraulic machine

A. causes noise and vibration of various parts
B. reduces the discharge of a turbine
C. causes sudden drop in power output and efficiency
D. all of the above
Answer» D. all of the above
24.

The principle of jet propulsion is used in driving the ships and aeroplanes.

A. Correct
B. Incorrect
Answer» A. Correct
25.

Which of the following statement is correct as regard to water wheels?

A. They have slow speeds.
B. They are suitable even for low water heads
C. They give constant efficiency, even if the discharge is not constant.
D. all of the above
Answer» D. all of the above
26.

If the ratio of corresponding velocities at corresponding points are equal, then the model and the prototype are said to have dynamic similarity.

A. Right
B. Wrong
Answer» B. Wrong
27.

Dynamic similarity is said to exist between the model and the prototype, if both of them

A. have identical velocities
B. are equal in size and shape
C. are identical in shape, but differ only in size
D. none of the above
Answer» D. none of the above
28.

The speed of an imaginary turbine, identical with the fiven turbine, which will develop a unit power under a unit head, is known as

A. normal speed
B. unit speed
C. specific speed
D. none of these
Answer» C. specific speed
29.

Which of the following pump is sucessfully used for lifting water to the wells?

A. Centrifugal pump
B. Reciprocating pump
C. Jet pump
D. Air-lift pump
Answer» D. Air-lift pump
30.

Which of the following pump is preferred for flood control and irrigation applications?

A. Centrifugal pump
B. Axial flow pump
C. Mixed flow pump
D. Reciprocating pump
Answer» B. Axial flow pump
31.

In a centrifugal pump, the regulating valve is provided on the

A. casing
B. delivery pipe
C. suction pipe
D. impeller
Answer» B. delivery pipe
32.

In a reciprocating pump, air vessels are fitted to the suction pipe and deliver pipe close to the cylinder of the pump.

A. True
B. False
Answer» A. True
33.

For 450 m head of water,

A. Pelton wheel
B. Kaplan turbine
C. Francis turbine
D. none of these
Answer» A. Pelton wheel
34.

Delivery head of a centrifugal pump is

A. directly proportional to N
B. inversely proportional to N
C. directly proportional to N2
D. inversely proportional to N2
Answer» C. directly proportional to N2
35.

The discharge through a turbine is

A. directly proportional to H1/2
B. inversely proportional to H1/2
C. directly proportional to H3/2
D. inversely proportional to H3/2
Answer» A. directly proportional to H1/2
36.

The flow ratio of Francis turbine is defined as the ratio of the

A. velocity of flow at inlet to the theoretical jet velocity
B. theoretical velocity of jet to the velocity of flow at inlet
C. velocity of runner at inlet to the velocity of flow at inlet
D. none of the above
Answer» A. velocity of flow at inlet to the theoretical jet velocity
37.

A Kaplan turbine is preferred for a specific speed of 300 to 1000 r.p.m.

A. Yes
B. No
Answer» A. Yes
38.

Which of the following is not a reaction turbine?

A. Furneyron turbine
B. Jonval turbine
C. Thomson's turbine
D. Pelton wheel
Answer» D. Pelton wheel
39.

A hydraulic ram is a device used to

A. store the energy of water
B. increase the pressure of water
C. to lift water from deep wells
D. to lift small quantity of water to a greater height when a large quantity of water is available at a smaller height
Answer» D. to lift small quantity of water to a greater height when a large quantity of water is available at a smaller height
40.

In a mixed flow centrifugal pump, the flow through the impeller is a combination of radial and axial flows.

A. Correct
B. Incorrect
Answer» A. Correct
41.

In an impulse turbine, the pressure of water both at entering and leaving the vanes, is atmospheric.

A. Agree
B. Disagree
Answer» A. Agree
42.

Which of the following pump is suitable for small discharge and high heads?

A. Centrifugal pump
B. Axial flow pump
C. Mixed flow pump
D. Reciprocating pump
Answer» D. Reciprocating pump
43.

In a Kaplan turbine runner, the number of blades are generally between

A. 2 to 4
B. 4 to 8
C. 8 to 16
D. 16 to 24
Answer» B. 4 to 8
44.

A turbine develops 10000 kW under a head of 25 metres at 135 r.p.m. Its specific speed is

A. 175.4 r.p.m.
B. 215.5 r.p.m.
C. 241.5 r.p.m.
D. 275.4 r.p.m.
Answer» C. 241.5 r.p.m.
45.

Which of the following trubine is preferred for 0 to 25 m head of water?

A. Pelton wheel
B. Kaplan turbine
C. Francis turbine
D. none of these
Answer» B. Kaplan turbine
46.

The overshot water wheels are those in which the wheel runs entirely by the

A. weight
B. impulse
Answer» A. weight
47.

In order to avoid cavitation in centrifugal pumps

A. the suction pressure should be high
B. the delivery pressure should be high
C. the suction pressure should be low
D. the delivery pressure should be low
Answer» A. the suction pressure should be high
48.

Manometric head, in case of a centrifugal pump, is equal to

A. Suction lift + Loss of head in suction pipe due to driction + Delivery lift + Loss of head in delivery pipe due to friction + Velocity head in the delivery pipe
B. Workdone per kN of water - Losses within the impeller
C. Energy per kN at outlet of impeller - Energy per kN at inlet of impeller
D. all of the above
Answer» D. all of the above
49.

A hydraulic coupling belongs to the category of

A. power absorbing machines
B. power developing machines
C. energy transfer machines
D. energy generating machines
Answer» C. energy transfer machines
50.

Overall efficiency of a centrifugal pump is the ratio of

A. energy available at the impeller to the energy supplied to the pump by the prime mover
B. actual workdone by the pump to the energy supplied to the pump by the prime mover
C. energy supplied to the pump to the energy available at the impeller
D. manometric head to the energy supplied by the impeller per kN of water
Answer» B. actual workdone by the pump to the energy supplied to the pump by the prime mover
51.

A hydraulic press is a device used

A. to store pressure energy which may be supplied to a machine later on
B. to increase the intensity of pressure of water by means of energy available from a large quantity of water at a low pressure
C. to lift larger load by the application of a comparatively much smaller force
D. all of the above
Answer» C. to lift larger load by the application of a comparatively much smaller force
52.

Power required to drive a centrifugal pump is

A. directly
B. inversely
Answer» A. directly
53.

Slip of a reciprocating pump is defined as the

A. ratio of actual discharge to the theoretical discharge
B. sum of actual discharge and the theoretical discharge
C. difference of theoretical discharge and the actual discharge
D. product of theoretical discharge and the actual discharge
Answer» C. difference of theoretical discharge and the actual discharge
54.

Work done by a turbine

A. depends
B. does not depend
Answer» A. depends
55.

The type of centrifugal pump preferred for a specific speed of 20 r.p.m. is

A. slow speed pump with radial flow at outlet
B. medium speed pump with radial flow at outlet
C. high speed pump with radia flow at outlet
D. high speed pump with axial flow at outlet
Answer» A. slow speed pump with radial flow at outlet
56.

Power required to drive a centrifugal pump is directly proportional to

A. diameter
B. square of diameter
C. cube of diameter
D. fourth power of diameter
Answer» D. fourth power of diameter
57.

The cavitation in a hydraulic machine is mainly due to

A. low velocity
B. high velocity
C. low pressure
D. high pressure
Answer» C. low pressure
58.

The overall efficiency of a reaction turbine is the ratio of

A. power produced by the turbine to the energy actually suppied by the turbine
B. actual work available at the turbine to the energy imparted to the wheel
C. workdone on the wheel to the energy (or head of water) actually supplied to the turbine
D. none of the above
Answer» A. power produced by the turbine to the energy actually suppied by the turbine
59.

A Francis turbine is used when the available head of water is

A. 0 to 25 m
B. 25 m to 250 m
C. above 250 m
D. none of these
Answer» B. 25 m to 250 m
60.

The cavitation in reaction turbines is avoided, to a great extent by

A. installing the turbine below the tail race level
B. using stainless steel runner of the turbine
C. providing highly polished blades to the runner
D. all of the above
Answer» D. all of the above
61.

A hydraulic intensifier is a device used to increase the intensity of pressure of water by means of energy available from a large quantity of water at a low pressure.

A. Right
B. Wrong
Answer» A. Right
62.

In a reaction turbine, the water enters the wheel under pressure and flows over the vanes.

A. Correct
B. Incorrect
Answer» A. Correct
63.

The efficiency of jet propulsion for a ship with inlet orifices at right angles to the direction of motion of ship, will be maximum when the relative velocity of the jet and ship is equal to twice the velocity of the ship.

A. Yes
B. No
Answer» A. Yes
64.

In the above question, the unit speed of the wheel is

A. 10 r.p.m.
B. 20 r.p.m.
C. 40 r.p.m.
D. 80 r.p.m.
Answer» B. 20 r.p.m.
65.

The specific speed of a centrifugal pump may be defined as the speed of an imaginary pump, identical with the given pump, which will discharge one litre of water, while it is being raised through a head of one metre.

A. True
B. False
Answer» A. True
66.

In a centrifugal pump, the water enters the impeller

A. axially
B. radially
Answer» B. radially
67.

In the above question, the saving in case of a double acting reciprocating pump is

A. 39.20%
B. 48.80%
C. 84.80%
D. 88.40%
Answer» A. 39.20%
68.

The specific speed from 160 to 500 r.p.m. of a centrifugal pump indicates that the pump is

A. slow speed with radial flow at outlet
B. medium speed with radial flow at outlet
C. high speed with radial flow at outlet
D. high speed with axial flow at outlet
Answer» D. high speed with axial flow at outlet
69.

The hydraulic efficiency of a reaction turbine, is the ratio of

A. power produced by the turbine to the energy actually supplied by the turbine
B. actual work available at the turbine to energy imparted to the wheel
C. workdone on the wheel to the energy (or head of water) actually supplied to the turbine
D. none of the above
Answer» C. workdone on the wheel to the energy (or head of water) actually supplied to the turbine
70.

Kinematic similarity is said to exist between the model and the prototype, if both of them

A. have identical velocities
B. are equal in size and shape
C. are identical in shape, but differ only in size
D. have identical forces
Answer» A. have identical velocities
71.

By fitting an air vessel to the reciprocating pump, there is always a saving of work done and subsequently saving of power. This saving in case of a single acting reciprocating pump is

A. 39.20%
B. 48.80%
C. 84.80%
D. 88.40%
Answer» C. 84.80%
72.

The discharge through a reaction turbine

A. remains same
B. increases
C. decreases
Answer» C. decreases
73.

The power produced by the reaction turbine is

A. directly proportional
B. inversely proportional
Answer» A. directly proportional
74.

A hydraulic accumulator is a device used to store

A. strain
B. pressure
C. kinetic
Answer» B. pressure
75.

Braking jet in an impulse turbine is used

A. to break the jet of water
B. to bring the runner to rest in a short time
C. to change the direction of runner
D. none of the above
Answer» B. to bring the runner to rest in a short time
76.

Mechanical efficiency of a centrifugal pump is the ratio of

A. energy available at the impeller to the energy supplied to the pump by the prime mover
B. actual workdone by the pump to the energy supplied to the sump by the prime mover
C. energy supplied to the pump to the energy available at the impeller
D. manometric head to the energy supplied by the impeller per kN of water
Answer» A. energy available at the impeller to the energy supplied to the pump by the prime mover
77.

The impeller of a centrifugal pump may have

A. volute casing
B. volute casing with guide blades
C. vortex casing
D. any one of these
Answer» D. any one of these
78.

In a mixed flow reaction turbine, the flow of water is partly radial and partly axial.

A. Correct
B. Incorrect
Answer» A. Correct
79.

The efficiency of a centrifugal pump will be maximum when the blades are bent backward.

A. Yes
B. No
Answer» A. Yes
80.

The specific speed of a hydraulic turbine depends upon

A. speed and power developed
B. discharge and power developed
C. speed and head of water
D. speed, power developed and head of water
Answer» D. speed, power developed and head of water
81.

The speed ratio of a Francis turbine is defined as the ratio of the theoretical jet velocity to the peripheral speed at inlet.

A. Yes
B. No
Answer» B. No
82.

A jet of water is striking at the centre of a curved vane moving with a uniform velocity in the direction of jet. For the maximum efficiency, the vane velocity is

A. one-half
B. one-third
C. two-third
D. three-fourth
Answer» B. one-third
83.

Slip of a reciprocating pump is negative, when

A. suction pipe is short and pump is running at low speeds
B. delivery pipe is long and pump is running at high speeds
C. suction pipe is short and delivery pipe is long and the pump is running at low speeds
D. suction pipe is long and delivery pipe is short and the pump is running at high speeds
Answer» D. suction pipe is long and delivery pipe is short and the pump is running at high speeds
84.

The overall efficiency for a Pelton wheel lies between

A. 0.50 to 0.65
B. 0.65 to 0.75
C. 0.75 to 0.85
D. 0.85 to 0.90
Answer» D. 0.85 to 0.90
85.

Which of the following statement is wrong?

A. The reaction turbines are used for low head and high discharge.
B. The angle of taper on draft tube is less than 8?
C. An impulse turbine is generally fitted slightly above the tail race.
D. A Francis turbine is an impulse turbine.
Answer» D. A Francis turbine is an impulse turbine.
86.

In a reaction turbine, the draft tube is used

A. to run the turbine full
B. to prevent air to enter the turbine
C. to increase the head of water by an amount equal to the height of the runner outlet above the tail race
D. to transport water to downstream
Answer» C. to increase the head of water by an amount equal to the height of the runner outlet above the tail race
87.

For centrifugal pump impeller, the maximum value of the vane exit angle is

A. 10? to 15?
B. 15? to 20?
C. 20? to 25?
D. 25? to 30?
Answer» C. 20? to 25?
88.

When the speed of the pump increases, its net positive suction head (NPSH) requirement decreases.

A. Agree
B. Disagree
Answer» B. Disagree
89.

Which of the following is not an impulse turbine?

A. Girad turbine
B. Turgo turbine
C. Pelton wheel
D. Kaplan turbine
Answer» D. Kaplan turbine
90.

In an axial flow reaction turbine, the water flows

A. parallel
B. perpendicular
Answer» A. parallel
91.

The depth of the bucket for a Pelton wheel is generally

A. equal to
B. 1.2 times
C. 1.8 times
D. double
Answer» B. 1.2 times
92.

The width of the bucket for a Pelton wheel is generally

A. double
B. three times
C. four times
D. five times
Answer» D. five times
93.

The speed of a turbine runner is

A. directly proportional to H1/2
B. inversely proportional to H1/2
C. directly proportional to H3/2
D. inversely proportional to H3/2
Answer» A. directly proportional to H1/2
94.

The hydraulic efficiency of an impulse turbine is the

A. ratio of the actual power produced by the turbine to the energy actually supplied by the turbine
B. ratio of the actual work available at the turbine to the energy imparted to the wheel
C. ratio of the work done on the wheel to the energy of the jet
D. none of the above
Answer» C. ratio of the work done on the wheel to the energy of the jet
95.

Which of the following pump is generally used to pump highly viscous fluid?

A. Centrifugal pump
B. Reciprocating pump
C. Air lift pump
D. Screw pump
Answer» D. Screw pump
96.

An impulse turbine is used for

A. low head of water
B. high head of water
C. medium head of water
D. high discharge
Answer» B. high head of water
97.

In an inward flow reaction turbine

A. the water flows parallel to the axis of the wheel
B. the water enters at the centre of the wheel and then flows towards the outer periphery of the wheel
C. the water enters the wheel at the outer periphery and then flows towards the centre of the wheel
D. the flow of water is partly radial and partly axial
Answer» C. the water enters the wheel at the outer periphery and then flows towards the centre of the wheel
98.

The specific speed of a turbine is the speed of an imaginary turbine, identical with the given turbine, which

A. delivers unit discharge under unit head
B. delivers unit discharge under unit speed
C. develops unit power under unit head
D. develops unit power under unit speed
Answer» C. develops unit power under unit head
99.

The jet ratio is defined as the ratio of the

A. diameter of jet to the diameter of Pelton wheel
B. velocity of jet to the velocity of Pelton wheel
C. diameter of Pelton wheel to the diameter of jet
D. velocity of Pelton wheel to the velocity of jet
Answer» C. diameter of Pelton wheel to the diameter of jet
100.

The Furneyron turbine is

A. an axial flow
B. an inward flow
C. an outward flow
D. a mixed flow
Answer» C. an outward flow
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