1000+ Hydraulics & Fluid Machineries Multiple Choice Question Answer [Solved]

1. Medium specific speed of turbine implies it is
A. Propeller turbine
B. Francis turbine
C. Impulse turbine
D. Any one of the above
Answer : B

2. 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

3. Which of the following turbine 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

4. 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 (where a = Area of the jet, Vr = Relative velocity of the jet and ship = V + v, v = Velocity of the ship, and V = Velocity of the jet issuing from the ship)
A. waVr /g × (Vr + v)
B. waVr /g × (Vr - v)
C. waVr /g × (Vr + v)²
D. waVr /g × (Vr - v)²
Answer : B

5. The Thomson's turbine is __________ reaction turbine.
A. An axial flow
B. An inward flow
C. An outward flow
D. A mixed flow
Answer : B

6. Discharge (Q) of a centrifugal pump is given by (where D = Diameter of impeller at inlet, b = Width of impeller at inlet, and Vf = Velocity of flow at inlet)
A. Q = ?.D.Vf
B. Q = ?.b.Vf
C. Q = ?.D.bf.V
D. Q = D.b.Vf
Answer : C

7. 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

8. 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

9. By fitting an air vessel to the reciprocating pump, there is always a saving of work done and subsequently saving of power. The saving in case of a double acting reciprocating pump is
A. 39.2 %
B. 48.8 %
C. 84.8 %
D. 88.4 %
Answer : A

10. The discharge through a reaction turbine with increase in unit speed
A. Increases
B. Decreases
C. Remain unaffected
D. First increases and then decreases
Answer : B

11. The working of which of the following hydraulic units is based on Pascal's law?
A. Air lift pump
B. Jet pump
C. Hydraulic coupling
D. Hydraulic press
Answer : D

12. The flow rate in gear pump
A. Increases with increase in pressure
B. Decreases with increase in pressure
C. More or less remains constant with increase in pressure
D. Unpredictable
Answer : C

13. 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
A. [wa (V - v)]/2g
B. [wa (V - v)]/g
C. [wa (V - v)²]/2g
D. [wa (V - v²)]/g
Answer : D

14. Head developed by a centrifugal pump depends on
A. Impeller diameter
B. Speed
C. Fluid density
D. Both (A) and (B) above
Answer : D

15. 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

16. In reaction turbine, draft tube is used
A. To transport water downstream without eddies
B. To convert the kinetic energy to flow energy by a gradual expansion of the flow cross-section
C. For safety of turbine
D. To increase flow rate
Answer : B

17. Pressure intensifier increases the pressure in proportion to
A. Ratio of diameters
B. Square of ratio of diameters
C. Inverse ratio of diameters
D. Square of inverse ratio of diameters
Answer : B

18. In centrifugal pumps, maximum efficiency is obtained when the blades are
A. Straight
B. Bent forward
C. Bent backward
D. Radial
Answer : C

19. 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 radial flow at outlet
D. High speed pump with axial flow at outlet
Answer : A

20. If the ratios of all the corresponding linear dimensions are equal, then the model and the prototype are said to have
A. Geometric similarity
B. Kinematic similarity
C. Dynamic similarity
D. None of these
Answer : A

21. 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

22. 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

23. 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

24. Puck up the wrong statement about centrifugal pump
A. Discharge a diameter
B. Head a speed²
C. Head a diameter
D. Power a speed?
Answer : A

25. Medium specific speed of a pump implies it is
A. Centrifugal pump
B. Mixed flow pump
C. Axial flow pump
D. Any one of the above
Answer : B

26. A turbine pump is basically a centrifugal pump equipped additionally with
A. Adjustable blades
B. Backward curved blades
C. Vaned diffusion casing
D. Inlet guide blades
Answer : C

27. Power required to drive a centrifugal pump is directly proportional to ________ of its impeller.
A. Diameter
B. Square of diameter
C. Cube of diameter
D. Fourth power of diameter
Answer : D

28. According to fan laws, for fans having constant wheel diameter, the pressure varies
A. Directly as fan speed
B. Square of fan speed
C. Cube of fan speed
D. Square root of fan speed
Answer : B

29. 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

30. Centrifugal pump is started with its delivery valve
A. Kept fully closed
B. Kept fully open
C. Irrespective of any position
D. Kept 50% open
Answer : A

31. 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

32. 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

33. The function of guide vanes in a reaction turbine is to
A. Allow the water to enter the runner without shock
B. Allow the water to flow over them, without forming eddies
C. Allow the required quantity of water to enter the turbine
D. All of the above
Answer : D

34. Low specific speed of a pump implies it is
A. Centrifugal pump
B. Mixed flow pump
C. Axial flow pump
D. None of the above
Answer : A

35. 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

36. The force exerted by a jet of water (in a direction normal to flow) impinging on a fixed plate inclined at an angle ? with the jet is
A. waV/2g × sin?
B. waV/g × sin?
C. waV²/2g × sin2?
D. waV²/g × sin?
Answer : C

37. The discharge of a double acting reciprocating pump is (where L = Length of stroke, A = Cross-sectional area of piston, and N = Speed of crank in r.p.m.)
A. L.A.N
B. 2 L.A.N
C. (L.A.N)/60
D. (2 L.A.N)/60
Answer : D

38. 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

39. Which type of the pump is different from others in the same group?
A. Screw pump
B. Gear pump
C. Cam and piston pump
D. Plunger pump
Answer : D

40. The power developed by a turbine is (where H = Head of water under which the turbine is working)
A. Directly proportional to H^1/2
B. Inversely proportional to H^1/2
C. Directly proportional to H^3/2
D. Inversely proportional to H^3/2
Answer : C

41. Multistage centrifugal pumps are used to
A. Give high discharge
B. Produce high heads
C. Pump viscous fluids
D. All of these
Answer : B

42. 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 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

43. One horsepower is equal to
A. 102 watts
B. 75 watts
C. 550 watts
D. 735 watts
Answer : D

44. The specific speed of a turbine is given by the equation
A. N?P / H^3/2
B. N?P / H²
C. N?P / H^5/4
D. N?P / H³
Answer : C

45. For 450 m head of water, _________ shall be used.
A. Pelton wheel
B. Kaplan turbine
C. Francis turbine
D. None of these
Answer : A

46. For starting an axial flow pump, its delivery valve should be
A. Closed
B. Open
C. Depends on starting condition and flow desired
D. Could be either open or closed
Answer : B

47. 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

48. In impulse Turbine, energy available at the inlet is in the form of
A. Potential Energy
B. Strain Energy
C. Kinetic energy
D. None of these
Answer : C

49. Discharge of a centrifugal pump is
A. Directly proportional to diameter of its impeller
B. Inversely proportional to diameter of its impeller
C. Directly proportional to (diameter)² of its impeller
D. Inversely proportional to (diameter)² of its impeller
Answer : D

50. Reciprocating pumps are no more to be seen in industrial applications (in comparison to centrifugal pumps) because of
A. High initial and maintenance cost
B. Lower discharge
C. Lower speed of operation
D. Necessity of air vessel
Answer : A