Hydraulics & Fluid Machineries 1000+ MCQ with answer for IBPS PO

1. 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

2. 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

3. Maximum impulse will be developed in hydraulic ram when
A. Waste valve closes suddenly
B. Supply pipe is long
C. Supply pipe is short
D. Ram chamber is large
Answer : A

4. High 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 : C

5. 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

6. 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

7. 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

8. 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

9. 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

10. Any change in load is adjusted by adjusting following parameter on turbine
A. Net head
B. Absolute velocity
C. Blade velocity
D. Flow
Answer : D

11. If a pump is handling water and is discharging a certain flow Q at a constant total dynamic head requiring a definite B.H.P., the same pump when handling a liquid of specific gravity 0.75 and viscosity nearly same as of water would discharge
A. Same quantity of liquid
B. 0.75 Q
C. Q/0.75
D. 1.5 Q
Answer : A

12. 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

13. 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

14. Casting of a centrifugal pump is designed so as to minimize
A. Friction loss
B. Cavitations
C. Static head
D. Loss of kinetic energy
Answer : D

15. 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
A. 2V/(v_r - v)
B. 2V/(v_r + v)
C. V/(v_r - v)
D. V/(v_r + v)
Answer : B

16. The maximum efficiency of jet propulsion of a ship with inlet orifices at right angles to the direction of motion of ship, is
A. 40 %
B. 50 %
C. 60 %
D. 80 %
Answer : B

17. 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

18. Which of the following pump is successfully used for lifting water to the boilers?
A. Centrifugal pump
B. Reciprocating pump
C. Jet pump
D. Airlift pump
Answer : C

19. The specific speed of turbine is defined as the speed of a unit
A. Of such a size that it delivers unit discharge at unit head
B. Of such a size that it delivers unit discharge at unit power
C. Of such a size that it requires unit power per unit head
D. Of such a size that it produces unit horse power with unit head
Answer : D

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. The optimum value of vane exit angle for a centrifugal pump impeller is
A. 10-15°
B. 20-25°
C. 30-40°
D. 50-60°
Answer : B

27. The depth of the bucket for a Pelton wheel is generally ________ the diameter of jet.
A. Equal to
B. 1.2 times
C. 1.8 times
D. Double
Answer : B

28. 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

29. Power required (in watts) to drive a centrifugal pump is (where H_m = Manometric head in metres, w = Specific weight in N/m³, Q = Discharge of the pump in m³/s, and ?_o = Overall efficiency of the pump)
A. (w H_m) / (Q × ?_o)
B. (w H_m Q) / ?_o
C. (w Q) / (H_m × ?_o)
D. (w Q ?_o) / H_m
Answer : B

30. 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

31. The relation between hydraulic efficiency (?_h), mechanical efficiency (?_m) and overall efficiency (?_o) is
A. ?_h = ?_o × ?_m
B. ?_m = ?_m × ?_h
C. ?_o = ?_h × ?_m
D. None of these
Answer : C

32. 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

33. The number of buckets on the periphery of a Pelton wheel is given by
A. (D/2d) + 5
B. (D/2d) + 10
C. (D/2d) + 15
D. (D/2d) + 20
Answer : C

34. 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

35. 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

36. 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

37. 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

38. 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

39. 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

40. 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

41. 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
A. One-half
B. One-third
C. Two-third
D. Three-fourth
Answer : B

42. The speed of a turbine runner is
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 : 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 discharge of wheel is
A. 0.25 m³/s
B. 0.5 m³/s
C. 1.5 m³/s
D. 2.5 m³/s
Answer : A

44. The efficiency of a hydraulic press is given by (where W = Weight lifted by ram, P = Force applied on plunger, A = Area of ram, and a = Area of plunger)
A. (W/p) × (A/a)
B. (p/W) × (a/A)
C. (W/p) × (a/A)
D. (p/W) × (A/a)
Answer : C

45. Which of the following is not an impulse turbine?
A. Girad turbine
B. Turgo turbine
C. Pelton wheel
D. Kaplan turbine
Answer : D

46. 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

47. 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

48. According to fan laws, for the fans having constant wheel diameters, the power demand varies
A. Directly as fan speed
B. Square of fan speed
C. Cube of fan speed
D. Square root of fan speed
Answer : C

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

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