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

1. Which of the following pump is successfully used for lifting water from deep wells?
A. Centrifugal pump
B. Reciprocating pump
C. Jet pump
D. Air lift pump
Answer : D

2. For very high discharge at low pressure such as for flood control and irrigation applications, following type of pump is preferred
A. Centrifugal
B. Axial flow
C. Reciprocating
D. Mixed flow
Answer : B

3. 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

4. The unit power developed by a turbine is (where P = Power developed by the turbine under a head of water (H).
A. P/ ?H
B. P/ H
C. P/ H^3/2
D. P/ H²
Answer : C

5. The maximum hydraulic efficiency of an impulse turbine is (where ? = Angle of blade tip at outlet)
A. (1 + cos ?)/2
B. (1 - cos ?)/2
C. (1 + sin ?)/2
D. (1 - sin ?)/2
Answer : A

6. The static head of a centrifugal pump is equal to the ________ of suction head and delivery head.
A. Product
B. Difference
C. Sum
D. None of these
Answer : C

7. A hydraulic intensifier normally consists of
A. Two cylinders, two rams and a storage device
B. A cylinder and a ram
C. Two coaxial rams and two cylinders
D. A cylinder, a piston, storage tank and control valve
Answer : C

8. In a Francis turbine runner, the numbers of blades are generally between
A. 2 to 4
B. 4 to 8
C. 8 to 16
D. 16 to 24
Answer : D

9. 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

10. 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

11. The angle of taper on draft tube is
A. Greater than 15°
B. Greater than 8°
C. Greater than 5°
D. Less than 8°
Answer : D

12. If the net positive suction head (NPSH) requirement for the pump is not satisfied, then
A. No flow will take place
B. Cavitation will be formed
C. Efficiency will be low
D. Excessive power will be consumed
Answer : B

13. Which of the following statement is correct?
A. In an impulse turbine, the water impinges on the buckets with pressure energy.
B. In a reaction turbine, the water glides over the moving vanes with kinetic energy.
C. In an impulse turbine, the pressure of the flowing water remains unchanged and is equal to atmospheric pressure.
D. In a reaction turbine, the pressure of the flowing water increases after gliding over the vanes.
Answer : C

14. 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

15. 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

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. High specific speed of turbine implies it is
A. Propeller turbine
B. Francis turbine
C. Impulse turbine
D. None of the above
Answer : A

18. 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

19. 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

20. According to fan laws, at constant pressure, the speed capacity and power vary
A. Directly as the air or gas density
B. Inversely as square root of density
C. Inversely as density
D. As square of density
Answer : B

21. The speed ratio in case of Francis turbine varies from
A. 0.15 to 0.3
B. 0.4 to 0.5
C. 0.6 to 0.9
D. 1 to 1.5
Answer : C

22. The efficiency of a Pelton wheel working under constant head ________ with the increase in power.
A. Remain same
B. Increases
C. Decreases
D. None of these
Answer : B

23. Specific speed for reaction turbines ranges from
A. 0 to 4.5
B. 10 to 100
C. 80 to 200
D. 250 to 300
Answer : B

24. 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

25. 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

26. Which place in hydraulic turbine is most susceptible for cavitations?
A. Inlet of draft rube
B. Blade inlet
C. Guide blade
D. Penstock
Answer : A

27. 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

28. The centrifugal pump preferred for a specific speed between 80 to 160 r.p.m. 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 mixed flow at outlet
Answer : D

29. The flow ratio in case of Francis turbine varies from
A. 0.15 to 0.3
B. 0.4 to 0.5
C. 0.6 to 0.9
D. 1 to 1.5
Answer : A

30. The maximum number of jets generally employed in impulse turbine without jet interference is
A. 4
B. 6
C. 8
D. 12
Answer : B

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

32. Which of the following turbine is preferred for a specific speed of 60 to 300 r.p.m.?
A. Pelton wheel
B. Francis turbine
C. Kaplan turbine
D. None of these
Answer : B

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

34. 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

35. The maximum number of jets, generally, employed in an impulse turbine without jet interference are
A. Two
B. Four
C. Six
D. Eight
Answer : C

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

37. The efficiency of jet propulsion for a ship with inlet orifices at right angles to the direction of motion of ship is given by
A. [2(V_r - v) v]/ V_r²
B. 2(V_r + v) v]/ V_r²
C. [(V_r - v) v]/ V_r
D. [(V_r + v) v]/ V_r
Answer : A

38. Reaction turbines are used for
A. Low head
B. High head
C. High head and low discharge
D. Low head and high discharge
Answer : D

39. A hydraulic accumulator is a device used to store ________ energy which may be supplied to a machine later on.
A. Strain
B. Pressure
C. Kinetic
D. None of these
Answer : B

40. 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

41. 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

42. Francis turbine is best suited for
A. Medium head application from 24 to 180 m
B. Low head installation up to 30 m
C. High head installation above 180 m
D. All types of heads
Answer : A

43. 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

44. 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

45. 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

46. 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

47. 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

48. 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

49. The cavitation in a hydraulic machine is mainly due to
A. Low velocity
B. High velocity
C. Low pressure
D. High pressure
Answer : C

50. The specific speed (Ns) of a centrifugal pump is given by
A. (N?Q)/H^2/3
B. (N?Q)/H^3/4
C. (N?Q)/H
D. (N?Q)/H^5/4
Answer : B