Hydraulic Machines MCQs Practice Set

1.The force exerted (in newton) by a jet of water impinging normally on a fixed plate is

• WaV/2g
• WaV/g
• WaV²/2g
• WaV²/g (Ans)

2. The force exerted by a jet of water impinging normally on a plate which due to the impact of jet, moves in the direction of jet with a velocity v is

• Wa(V -v)/2g
• Wa(V -v)/g
• Wa(V -v)²/2g
• Wa(V -v)²/g (Ans)

3.The ratio of the normal force of jet of water on a plate inclined at an angle of 30^o as compared to that when the plate is normal to jet, is

• 1/√2
• 1/2 (Ans)
• 1
• √2

4.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 ………………… of the jet velocity

• One-half
• One-third (Ans)
• Two-third
• Three-fourth

5.A ship with jet propulsion draws water through inlet orifices at right angles to the direction of its motion. The propelling force of the jet is

• waV_r/g(V_r+v)
• waV_r/g(V_r – v) (Ans)
• waV_r/g(V_r+v)²
• waV_r/g(V_r – v)²

Where               a = Area of the jet

V_r = Relative velocity of the jet and ship = V + v

v = Velocity of the ship, and

V = Velocity of the jet issuing from the ship

6.The efficiency of jet propulsion for a ship with inlet orifices at right angles to the direction of motion of ship is given by

• 2(V_r – v)v/V_r² (Ans)
• 2(V_r + v)v/V_r²
• (V_r – v)v/V_r
• (V_r + v)v/V_r

7.The maximum efficiency of jet propulsion of a ship with inlet orifices at right angles to the direction of motion of ship, is

• 40%
• 50% (Ans)
• 60%
• 80%

8.The water in a jet propelled boat is drawn through the openings facing the direction of motion of the boat. The efficiency of propulsion is given by

• 2v/V_r – v
• 2v/V_r + v (Ans)
• V/V_r – v
• V/V_r + v

9.The undershot water wheels are those in which

• The wheels run entirely by the weight of water
• The wheels run entirely by the impulse of water (Ans)
• The wheels run partly by the weight of water and by the impulse of water
• None of the above

10.The overshot water wheels are those in which the wheel runs entirely by the ………….. of water.

• Weight (Ans)
• Impulse

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

• They have slow speeds
• They are suitable even for low water heads
• They give constant efficiency, even if the discharge is not constant
• All of the above

12.Braking jet in an impulse turbine is used

• To break the jet of water
• To bring the runner to rest in a short time (Ans)
• To change the direction of runner
• None of these

13.Work done by a turbine ……………. Upon the weight of water flowing per second.

• Depends (Ans)
• Does not depends

14.A pelton wheel is

• Tangential flow impulse turbine (Ans)
• Inward flow impulse turbine
• Outward flow impulse turbine
• Inward flow reaction turbine

15.An impulse turbine is used for

• Low head of water
• High head of water (Ans)
• Medium head of water
• High discharge

16.The gross or total head of the turbine is the …………………. Of the water levels at the head race and tail race.

• Sum
• Difference (Ans)
• Product

17.If H_g is the gross or total head and h_f is the head lost due to friction, then net or effective head(H) is given by

• H = H_g / h_f
• H = H_g * h_f
• H = H_g + h_f
• H = H_g – h_f (Ans)

18.The hydraulic efficiency of an impulse turbine is the

• Ratio of the actual power produced by the turbine to the energy actually supplied by the turbine
• Ratio of the actual work available at the turbine to the energy imparted to the wheel
• Ratio of the work done on the wheel to the energy of the jet (Ans)
• None of the above

19.The mechanical efficiency of an impulse turbine is

• Ratio of the actual power produced by the turbine to the energy actually supplied by the turbine
• Ratio of the actual work available at the turbine to the energy imparted to the wheel (Ans)
• Ratio of the work done on the wheel to the energy of the jet
• None of the above

20.The hydraulic efficiency of an impulse turbine is maximum when velocity of wheel is ……………… of the jet velocity,

• One-fourth
• One-half (Ans)
• Three-fourth
• Double

21.The overall efficiency for a pelton wheel lies between

• 50 to 0.65
• 65 to 0.75
• 75 to 0.85
• 85 to 0.90 (Ans)

22.A double overhung pelton wheel has

• Two jets
• Two runners (Ans)
• Four jets
• Four runners

23.The width of the bucket for a pelton wheel is generally …………… the diameter of jet

• Double
• Three times
• Four times
• Five times (Ans)

24.The depth of the bucket for a pelton wheel is generally …………… the diameter of jet

• Equal to
• 2 times (Ans)
• 8 times
• Double

25.The jet ratio is defined as the ratio of the

• Diameter of jet to the diameter of pelton wheel
• Velocity of jet to the velocity of pelton wheel
• Diameter of pelton wheel to the diameter of jet (Ans)
• velocity of pelton wheel to the velocity of jet

26.Which of the following is not an impulse turbine?

• Girab turbine
• Turgo turbine
• Pelton wheel
• Kaplan turbine (Ans)

27.The number of buckets on the periphery of a pelton wheel is given by

• D/2d + 5
• D/2d + 10
• D/2d + 15 (Ans)
• D/2d + 20

28.The maximum number of jets, generally, employed in an impulse turbine without jet interference are

• Two
• Four
• Six (Ans)
• Eight

29.The function of guide vanes in a reaction turbine is to

• Allow the water to enter the runner without shock
• Allow the water to flow over them, without forming eddies
• Allow the required quantity of water to enter the turbine
• All of the above (Ans)

30.In a reaction turbine, the draft tube is used

• To run the turbine full
• To prevent air to enter the turbine
• To increase the head of water by an amount equal to the height of the runner outlet above the tail race (Ans)
• To transport water to downstream

31.If V₁ and V₂ are the velocities of water at inlet and outlet of the draft tube respectively, then the efficiency of a draft tube is

• V₁ – V₂ / V₁
• V₁² – V₂² / V₁² (Ans)
• V₁ / V₁ – V₂
• V₁²/ V₁² – V₂²

32.Which of the following statement is correct?

• In an impulse turbine, the water impinges on the buckets with pressure energy
• In a reaction turbine, the water glides over the moving with kinetic energy
• In an impulse turbine, the pressure of the flowing water remains unchanged and is equal to atmospheric pressure (Ans)
• In an reaction turbine, the pressure of the flowing water increases after glides over the vanes.

33.In an inward flow reaction turbine

• The water flows parallel to the axis of the wheel
• The water enters at the centre of the wheel and then flows towards the outer periphery of the wheel
• The water enters the wheel at the outer periphery and then flows towards the centre of the wheel (Ans)
• The flow of water is partly radial and partly axial

34.In an axial flow reaction turbine, the water flows …………… to the axis of the wheel

• Parallel (Ans)
• Perpendicular

35.In an outward flow reaction turbine

• The water flows parallel to the axis of the wheel
• The water enters at the centre of the wheel and then flows towards the outer periphery of the wheel (Ans)
• The water enters the wheel at the outer periphery and then flows towards the centre of the wheel
• The flow of water is partly radial and partly axial

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

• Power produced by the turbine to the energy actually supplied by the turbine
• Actual work available at the turbine to energy imparted to the wheel
• Workdone on the wheel to the energy (or head of water) actually supplied to the turbine (Ans)
• None of the above

37.The ratio of actual work available at the turbine to the energy imparted to the wheel is known as ………… efficiency

• Hydraulic
• Mechanical (Ans)
• Overall

38.The overall efficiency of a reaction turbine is the ratio of

• Power produced by the turbine to the energy actually supplied by the turbine (Ans)
• Actual work available at the turbine to energy imparted to the wheel
• Workdone on the wheel to the energy (or head of water) actually supplied to the turbine
• None of the above

39.In a Francis runner, the number of blades are generally between

• 2 to 4
• 4 to 8
• 8 to 16
• 16 to 24 (Ans)

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

• 2 to 4
• 4 to 8 (Ans)
• 8 to 16
• 16 to 24

41.Which of the following is not a reaction turbine?

• Furneyron turbine
• Jonval turbine
• Thomson’s turbine
• Pelton wheel (Ans)

42.The Furneyron turbine is ………………… reaction turbine

• An axial flow
• An inward flow
• An outward flow (Ans)
• A mixed flow

43.The Thomson’s turbine is ………………… reaction turbine

• An axial flow
• An inward flow (Ans)
• An outward flow
• A mixed flow

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

• Velocity of flow at inlet to the theoretical jet velocity (Ans)
• Theoretical velocity of jet to the velocity of flow at inlet
• Velocity of runner at inlet to the velocity of flow at inlet
• None of the above

45.The flow ratio in case of Francis turbine varies from

• 15 to 0.3 (Ans)
• 4 to 0.5
• 6 to 0.9
• 1 to 1.5

46.The power produced by the reaction turbine is …………………. To the head of water.

• Directly proportional (Ans)
• Inversely proportional

47.The speed ratio in case of Francis turbine varies from

• 15 to 0.3
• 4 to 0.5
• 6 to 0.9 (Ans)
• 1 to 1.5

48.The runaway speed of a hydraulic turbine is the speed

• At full load
• At which there will be no damage to the runner
• Corresponding to maximum overload permissible
• At which the turbine will run freely without load (Ans)

49.The power developed by a turbine is

• Directly proportional to H^1/2
• Inversely proportional to H^1/2
• Directly proportional to H^3/2 (Ans)
• Inversely proportional to H^3/2

Where              H = Head of water under which the turbine is working

50.The unit power developed by a turbine is

• P/√H
• P/H
• P/H^3/2 (Ans)
• P/H²

Where            P = Power developed by the turbine under a head of water(H)

51.The speed of a turbine runner is

• Directly proportional to H^1/2 (Ans)
• Inversely proportional to H^1/2
• Directly proportional to H^3/2
• Inversely proportional to H^3/2

52.The discharge through a turbine is

• Directly proportional to H^1/2 (Ans)
• Inversely proportional to H^1/2
• Directly proportional to H^3/2
• Inversely proportional to H^3/2

53.The unit speed of the turbine runner is

• N/√H (Ans)
• N/H
• N/H^3/2 (Ans)
• N/H²

54.The unit discharge through the turbine is

• Q/√H (Ans)
• Q/H
• Q/H^3/2 (Ans)
• Q/H²

55.The specific speed of a turbine is given by the equation

• N√P/ H^3/2
• N√P / H²
• N√P /H^5/4 (Ans)
• N√P /H³

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

• 10 r.p.m
• 20 r.p.m (Ans)
• 40 r.p.m
• 80 r.p.m

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

• Normal speed
• Unit speed
• Specific speed (Ans)
• None of these

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

• 4 r.p.m.
• 5 r.p.m.
• 5 r.p.m. (Ans)
• 4 r.p.m.

59.Which of the following turbine is preferred for a specific speed of 60 to 300 r.p.m.?

• Pelton wheel
• Francis turbine (Ans)
• Kaplan turbine
• None of these

60. Which of the following turbine is preferred for 0 to 25 m head of water?

• Pelton wheel
• Francis turbine
• Kaplan turbine (Ans)
• None of these

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

• 0 to 25 m
• 225m to 250 m (Ans)
• Above 250 m
• None of these

62.For 450 m head of water,…………….. shall be used

• Pelton wheel (Ans)
• Francis turbine
• Kaplan turbine
• None of these

63.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?

• Pelton wheel with one nozzle (Ans)
• Pelton wheel with two or more nozzles
• Kaplan turbine
• Francis turbine

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

• 26
• 36
• 46 (Ans)
• 56

65.The efficiency of a Pelton wheel working under constant head …………….. with the in crease in power

• Remains same
• Increases (Ans)
• Decreases

66.The discharge through a reaction turbine ……………. With the increase in unit speed

• Remains same
• Increases
• Decreases (Ans)

67.The cavitation in a hydraulic machine is mainly due to

• Low velocity
• High velocity
• Low pressure (Ans)
• High pressure

68.The cavitation in a hydraulic machine

• Causes noise and vibration of various parts
• Reduces the discharge of a turbine
• Causes sudden drop in power output and efficiency
• All of the above (Ans)

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

• Installing the turbine below the tail race level
• Using stainless steel runner of the turbine
• Providing highly polished blades to the runner
• All of the above (Ans)

70.The specific speed of a hydraulic turbine depends upon

• Speed and power developed
• Discharge and power developed
• Speed and head of water
• Speed, power developed and head of water (Ans)

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

• Delivers unit discharge under unit head
• Delivers unit discharge under unit speed
• Develops unit power under unit head (Ans)
• Develops unit power under unit speed

72.In a centrifugal pump, the water enters the impeller ………………….. and leaves the vanes axially.

• Axially
• Radially (Ans)

73.The impeller of a centrifugal pump may have

• Volute casing
• Volute casing with guide blades
• Vortex casing
• Any one of these (Ans)

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

• Suction left + loss of head in suction pipe due to friction + delivery lift + loss of head in delivery pipe due to friction + velocity head in the delivery pipe
• Workdone per kN of water – losses within the impeller
• Energy per kN at outlet of impeller – energy per kN at inlet of impeller
• All of the above (Ans)

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

• Casing
• Delivery pipe (Ans)
• Suction pipe
• Impeller

76.The static head of a centrifugal pump is equal to the ……………… of suction head and delivery head.

• Product
• Difference
• Sum (Ans)

77.Mechanical efficiency of a centrifugal pump is the ratio of

• Energy available at the impeller to the energy supplied to the pump by the prime mover (Ans)
• Actual workdone by the pump to the energy supplied to the pump by the prime mover
• Energy supplied to the pump to the energy available at the impeller
• Manometric head to the energy supplied by the impeller per kN of water

78.Overall efficiency of a centrifugal pump is the ratio of

• Energy available at the impeller to the energy supplied to the pump by the prime mover
• Actual workdone by the pump to the energy supplied to the pump by the prime mover (Ans)
• Energy supplied to the pump to the energy available at the impeller
• Manometric head to the energy supplied by the impeller per kN of water

79.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

• Manometric efficiency
• Mechanical efficiency
• Overall efficiency
• Volumetric efficiency (Ans)

80.Multi-stage centrifugal pumps are used to

• Give high discharge
• Produce high heads (Ans)
• Pump viscous fluids
• All of these

81.A centrifugal pump will start delivering liquid only when the pressure rise in the impeller is equal to the

• Kinetic head
• Velocity head
• Manometric head (Ans)
• Static head

82.The discharge of a double acting reciprocating pump is

• A.N
• 2 L.A.N
• A.N/60
• 2 L.A.N/60 (Ans)

Where                      L=Length of stroke

A= Cross-sectional area of piston, and

N= Speed of crank in r.p.m.

83.Slip of a reciprocating pump is defined as the

• Ratio of actual discharge to the theoretical discharge
• Sum of actual discharge and the theoretical discharge
• Difference of theoretical discharge and the actual discharge (Ans)
• Product of theoretical discharge and the actual discharge

84. Slip of a reciprocating pump is negative, when

• Suction pipe is short and pump is running at low speeds
• Delivery pipe is long and pump is running at long speeds
• Suction pipe is short and Delivery pipe is long and the pump is running at low speeds
• Suction pipe is long and Delivery pipe is short and the pump is running at high speeds (Ans)

85.Head developed by a centrifugal pump is

• Proportional to diameter of impeller
• Proportional to speed of impeller
• Proportional to diameter and speed of impeller (Ans)
• None of the above

86.Theoretical power required (in watts) to drive a reciprocating pump is

• wQH_S
• wQH_d
• wQ(H_{S –} H_d)
• wQ(H_{S +} H_d) (Ans)

87.In a reciprocating pump, air vessels are used to

• smoothen the flow
• reduce suction head
• increase delivery head
• reduce acceleration head (Ans)

88.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

• 2%
• 8%
• 8% (Ans)
• 4%

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

• 2% (Ans)
• 8%
• 8%
• 4%

90.Discharge is a centrifugal pump is

• Directly proportional to N (Ans)
• Inversely proportional to N
• Directly proportional to N²
• Inversely proportional to N²

Where               N= Speed of the pump impeller

91.Delivery head of a centrifugal pump is

• Directly proportional to N
• Inversely proportional to N
• Directly proportional to N² (Ans)
• Inversely proportional to N²

92.Discharge of a centrifugal pump is

• directly proportional to diameter of its impeller
• inversely proportional to diameter of its impeller
• directly proportional to (diameter)² of its impeller
• inversely proportional to (diameter)² of its impeller (Ans)

93.Power required to drive a centrifugal pump is directly proportional to …………………. Of its impeller.

• Diameter
• Square of diameter
• Cube of diameter
• Fourth power of diameter (Ans)

94.The specific speed (N_s) of a centrifugal pump is given by

• N√Q/ H^2/3
• N√Q / H^3/4 (Ans)
• N√Q /H
• N√Q /H^5/4

95.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

• 8 r.p.m.
• 2 r.p.m.
• 4 r.p.m. (Ans)
• 248 r.p.m.

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

• Slow speed pump with radial flow at outlet
• Medium speed pump with radial flow at outlet
• High speed pump with radial flow at outlet
• High speed pump with axial flow at outlet

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

• 10^o to 15^o
• 15^o to 20^o
• 20^o to 25^o (Ans)
• 25^o to 30^o

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

• Slow speed with radial flow at outlet
• Medium speed with radial flow at outlet
• High speed with radial flow at outlet
• High speed with axial flow at outlet (Ans)

99.If the net positive suction head (NPSH) requirement for the pump is not satisfied, then

• No flow will take place
• Cavitation will be formed (Ans)
• Efficiency will be low
• Excessive power will be consumed

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

• Centrifugal pump
• Axial flow pump
• Mixed flow pump
• Reciprocating pump (Ans)

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

• Centrifugal pump
• Axial flow pump (Ans)
• Mixed flow pump
• Reciprocating pump

102.The centrifugal pump preferred for a specific speed between 80 to 160 r.p.m. is

• Slow speed with radial flow at outlet
• Medium speed with radial flow at outlet
• High speed with radial flow at outlet
• High speed with mixed flow at outlet (Ans)

103.In order to avoid cavitation in centrifugal pumps

• The suction pressure should be high (Ans)
• The delivery pressure should be high
• The suction pressure should be low
• The delivery pressure should be low

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

• Centrifugal pump
• Reciprocating pump
• Air lift pump
• Screw pump (Ans)