Hydraulics & Fluid Machineries 1000+ MCQ with answer for DRDO

1. 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

2. 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

3. 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

4. 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

5. 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

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

8. In an outward flow reaction turbine
A. The water flows parallel to the axis of the wheel
B. The water enters at the centre of the wheel and then flows towards the outer periphery of the wheel
C. The water enters the wheel at the outer periphery and then flows towards the centre of the wheel
D. The flow of water is partly radial and partly axial
Answer : B

9. 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

10. 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

11. Discharge of a centrifugal pump is (where N = Speed of the pump impeller)
A. Directly proportional to N
B. Inversely proportional to N
C. Directly proportional to N²
D. Inversely proportional to N²
Answer : A

12. Multistage centrifugal pumps are used to obtain
A. High discharge
B. High head
C. Pumping of viscous fluids
D. High head and high discharge
Answer : B

13. Braking jet in an impulse turbine is used
A. To break the jet of water
B. To bring the runner to rest in a short time
C. To change the direction of runner
D. None of these
Answer : B

14. 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

15. Kinematic 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 : A

16. 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

17. 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

18. In a centrifugal pump, the liquid enters the pump
A. At the top
B. At the bottom
C. At the canter
D. From sides
Answer : C

19. According to fan laws, at constant speed and capacity, the pressure 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 : A

20. 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

21. 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

22. The width of the bucket for a Pelton wheel is generally ________ the diameter of jet.
A. Double
B. Three times
C. Four times
D. Five times
Answer : D

23. Which of the following pump is suitable for small discharge and high heads?
A. Centrifugal pump
B. Axial flow pump
C. Mixed flow pump
D. Reciprocating pump
Answer : D

24. The discharge through a turbine 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

25. Axial flow 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 : B

26. 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

27. 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

28. Which of the following pump is preferred for flood control and irrigation applications?
A. Centrifugal pump
B. Axial flow pump
C. Mixed flow pump
D. Reciprocating pump
Answer : B

29. The runaway speed of a hydraulic turbine is the speed
A. At full load
B. At which there will be no damage to the runner
C. Corresponding to maximum overload permissible
D. At which the turbine will run freely without load
Answer : D

30. 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

31. 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

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

33. Francis, Kaplan and propeller turbines fall under the category of
A. Impulse turbines
B. Reaction turbines
C. Axial flow turbines
D. Mixed flow turbines
Answer : B

34. 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

35. 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

36. 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

37. The ratio of actual work available at the turbine to the energy imparted to the wheel is known as ________ efficiency.
A. Hydraulic
B. Mechanical
C. Overall
D. None of these
Answer : B

38. 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

39. 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

40. 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

41. 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

42. 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

43. Guide angle as per the aerofoil theory of Kaplan turbine blade design is defined as the angle between
A. Lift and resultant force
B. Drag and resultant force
C. Lift and tangential force
D. Lift and drag
Answer : A

44. 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

45. 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

46. 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

47. 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

48. 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

49. 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

50. 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