1000+ Hydraulics & Fluid Machineries MCQ for NDA [Solved]

1. The discharge through a reaction turbine ________ with the increase in unit speed.
A. Decreases
B. Increases
C. Remain same
D. None of these
Answer : A

2. When a piping system is made up primarily of vertical lift and very little pipe friction, the pump characteristics should be
A. Horizontal
B. Nearly horizontal
C. Steep
D. First rise and then fall
Answer : C

3. 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

4. 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

5. Which of the following is not a reaction turbine?
A. Fourneyron turbine
B. Journal turbine
C. Thomson's turbine
D. Pelton wheel
Answer : D

6. The specific speed of a hydraulic turbine depends upon
A. Speed and power developed
B. Discharge and power developed
C. Speed and head of water
D. Speed, power developed and head of water
Answer : D

7. The unit speed of the turbine runner is
A. N/?H
B. N/H
C. N/H^3/2
D. N/H²
Answer : A

8. 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

9. 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

10. Which of the following pump is successfully used for lifting water to the turbines?
A. Centrifugal pump
B. Reciprocating pump
C. Jet pump
D. Air lift pump
Answer : C

11. 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

12. A Pelton wheel is
A. Tangential flow impulse turbine
B. Inward flow impulse turbine
C. Outward flow impulse turbine
D. Inward flow reaction turbine
Answer : A

13. Indicator diagram of a reciprocating pump is a graph between
A. Flow vs. swept volume
B. Pressure in cylinder vs. swept volume
C. Flow vs. speed
D. Pressure vs. speed
Answer : B

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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, the horse power required will be
A. Same
B. 0.75 B.H.P.
C. B.H.P./0.75
D. 1.5 B.H.P.
Answer : B

23. In axial flow fans and turbines, fluid enters and leaves as follows
A. Radially, axially
B. Axially, radially
C. Axially, axially
D. Radially, radially
Answer : C

24. 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

25. 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

26. The hydraulic efficiency of an impulse turbine is maximum when velocity of wheel is _______ of the jet velocity,
A. One-fourth
B. One-half
C. Three-fourth
D. Double
Answer : B

27. In a single casing, multistage pump running at constant speed, the capacity rating is to be slightly lowered. It can be done by
A. Designing new impeller
B. Trimming the impeller size to the required size by machining
C. Not possible
D. Some other alterations in the impeller
Answer : B

28. 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

29. 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

30. 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

31. 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

32. 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

33. 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

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

35. 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

36. 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

37. 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

38. According to fan laws, for fans having constant wheel diameter, the air or gas capacity varies
A. Directly as fan speed
B. Square of fan speed
C. Cube of fan speed
D. Square root of fan speed
Answer : A

39. 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

40. 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

41. The unit discharge through the turbine is
A. Q/?H
B. Q/H
C. Q/H^3/2
D. Q/H²
Answer : A

42. An impulse turbine is used for
A. Low head of water
B. High head of water
C. Medium head of water
D. High discharge
Answer : B

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

44. 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

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

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

47. Which of the following hydraulic unit is used for transmitting increased or decreased torque to the driven shaft?
A. Hydraulic ram
B. Hydraulic intensifier
C. Hydraulic torque converter
D. Hydraulic accumulator
Answer : C

48. A hydraulic press is a device used
A. To store pressure energy which may be supplied to a machine later on
B. To increase the intensity of pressure of water by means of energy available from a large quantity of water at a low pressure
C. To lift larger load by the application of a comparatively much smaller force
D. All of the above
Answer : C

49. 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

50. The ratio of the normal force of jet of water on a plate inclined at an angle of 30° as compared to that when the plate is normal to jet, is
A. 1/?2
B. 1/2
C. 1
D. ?2
Answer : B