About Hydraulic Machines

Following are some of the multiple choice questions on the Hydraulic Machines with answers that will help the students in developing their knowledge.

Hydraulic Machines MCQ

1. 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

2. Which of the following is not a rotary pump

  • Vane
  • Gear
  • Screw
  • Axial

3. A hydraulic coupling belongs to the category of

  • power absorbing machines
  • power developing machines
  • energy transfer machines
  • energy generating machines

4. A hydraulic press is a device used

  • To store pressure energy which may be supplied to a machine later on
  • To increase the intensity of pressure of water by means of energy available from a large quantity of water at a low pressure
  • To lift larger load by the application of a comparatively much smaller force
  • All of the above

5. A hydraulic ram is a device used to

  • Store the energy of water
  • Increase the pressure of water
  • To lift water from deep wells
  • To lift small quantity of water to a greater height when a large quantity of water is available at a smaller height

6. 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

7. The width of the bucket for a Pelton wheel is generally ________ the diameter of jet.

  • Double
  • Three times
  • Four times
  • Five times

8. The working of which of the following hydraulic units is based on Pascal's law?

  • Air lift pump
  • Jet pump
  • Hydraulic coupling
  • Hydraulic press

9. The flow in a pipe or channel is said to be non-uniform when

  • The liquid particles at all sections have the same velocities
  • The liquid particles at different sections have different velocities
  • The quantity of liquid flowing per second is constant
  • Each liquid particle has a definite path

10. The breast water wheels are those in which the wheel runs partly by the weight of water and partly by the impulse of water.

  • True
  • False

11. The force exerted by a jet of water (in a direction normal to flow) impinging on a fixed plate inclined at an angle θ with the jet is

  • ρaV2×sinθ
  • ρaV/2×sinθ
  • ρaV2/2×sin2θ
  • ρaV×sinθ

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

  • 10° to 15°
  • 15° to 20°
  • 20° to 25°
  • 25° to 30°

13. The unit of dynamic viscosity in S.I. units is

  • N-m/s²
  • N-s/m²
  • Poise
  • Stoke

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

  • True
  • False

15. When a cylindrical vessel, containing some liquid, is rotated about its vertical axis, the liquid surface is depressed down at the axis of its rotation and rises up near the walls of the vessel on all sides. This type of flow is known as

  • Steady flow
  • Turbulent flow
  • Vortex flow
  • Uniform flow

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

  • 0 to 25 m
  • 25 m to 250 m
  • Above 250 m
  • None of these

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

  • Correct
  • Incorrect

18. Which of the following pump is successfully used for lifting water from deep wells?

  • Centrifugal pump
  • Reciprocating pump
  • Jet pump
  • Air lift pump

19. Which of the following instrument can be used for measuring speed of an aeroplane?

  • Venturimeter
  • Orifice plate
  • Pitot tube
  • Rotameter

20. The length of the divergent cone in a Venturimeter is __________ that of the convergent cone.

  • Equal to
  • Double
  • Three to four times
  • Five to six times

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

  • Centrifugal pump
  • Axial flow pump
  • Mixed flow pump
  • Reciprocating pump

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

  • Pelton wheel
  • Kaplan turbine
  • Francis turbine
  • none of these

23. The overall 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 the 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

24. Work done by a turbine __________ upon the weight of water flowing per second.

  • depends
  • does not depend

25. Meta-centric height is given as the distance between

  • The center of gravity of the body and the metacenter
  • The center of gravity of the body and the center of buoyancy
  • The center of gravity of the body and the center of pressure
  • Center of buoyancy and metacenter

26. Which place in hydraulic turbine is most susceptible for cavitations?

  • Inlet of draft rube
  • Blade inlet
  • Guide blade
  • Penstock

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

  • Agree
  • Disagree

28. The flow of water through the hole in the bottom of a wash basin is an example of

  • Steady flow
  • Uniform flow
  • Free vortex
  • Forced vortex

29. Which of the following is an example of laminar flow?

  • Underground flow
  • Flow past tiny bodies
  • Flow of oil in measuring instruments
  • All of these

30. When a liquid is flowing through a pipe, the velocity of the liquid is

  • Maximum at the centre and minimum near the walls
  • Minimum at the centre and maximum near the walls
  • Zero at the centre and maximum near the walls
  • Maximum at the centre and zero near the walls

31. A flow in which each liquid particle has a definite path, and the paths of individual particles do not cross each other, is called

  • Steady flow
  • Uniform flow
  • Streamline flow
  • Turbulent flow

32. The angle of taper on draft tube is

  • Greater than 15°
  • Greater than 8°
  • Greater than 5°
  • Less than 8°

33. A glass tube of smaller diameter is used while performing an experiment for the capillary rise of water because

  • It is easier to see through the glass tube
  • Glass tube is cheaper than a metallic tube
  • It is not possible to conduct this experiment with any other tube
  • All of the above

34. The torque required to overcome viscous resistance of a footstep bearing is (where μ = Viscosity of the oil, N = Speed of the shaft, R = Radius of the shaft, and t = Thickness of the oil film)

  • μπ²NR/60t
  • μπ²NR²/60t
  • μπ²NR³/60t
  • μπ²NR⁴/60t

35. According to Newton's law of viscosity, the shear stress on a layer of a fluid is __________ to the rate of shear strain.

  • Equal to
  • Directly proportional
  • Inversely proportional
  • None of these

36. The discharge of a depressed nappe is 6 to 7 percent __________ that of a free nappe.

  • Less than
  • More than
  • Equal to
  • None of these

37. The force present in a moving liquid is

  • Inertia force
  • Viscous force
  • Gravity force
  • All of these

38. The product of mass and acceleration of flowing liquid is called

  • Inertia force
  • Viscous force
  • Gravity force
  • Pressure force

39. The property by virtue of which a liquid opposes relative motion between its different layers is called

  • Surface tension
  • Coefficient of viscosity
  • Viscosity
  • Osmosis

40. 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

41. 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%
  • 60%
  • 80%

42. 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.

  • True
  • False

43. A large Reynold number is indication of

  • Smooth and streamline flow
  • Laminar flow
  • Steady flow
  • Highly turbulent flow

44. The capillary rise at 20°C in a clean glass tube of 1 mm bore containing water is approximately

  • 5 mm
  • 10 mm
  • 20 mm
  • 30 mm

45. Motion of a liquid in a volute casing of a centrifugal pump is an example of

  • Rotational flow
  • Radial
  • Forced spiral vortex flow
  • Spiral vortex flow

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

  • Suction lift + 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

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

  • Agree
  • Disagree

48. Reynold's number is the ratio of inertia force to

  • Pressure force
  • Elastic force
  • Gravity force
  • Viscous force

49. Froude's number is the ratio of inertia force to

  • Pressure force
  • Elastic force
  • Gravity force
  • Surface tension force

50. 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

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