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

1. In a Kaplan 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 : B

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

3. 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

4. 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

5. Mechanical 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 : 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 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

7. 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

8. 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

9. In an inward 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 : C

10. 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

11. 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

12. Saving of work done and power by fitting an air vessel to single acting reciprocating pump is of the order of
A. 39.2 %
B. 49.2 %
C. 68.8 %
D. 84.8 %
Answer : D

13. 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

14. 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

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

16. 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

17. 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

18. Air vessels in reciprocating pump are used to
A. Smoothen flow
B. Reduce acceleration to minimum
C. Increase pump efficiency
D. Save pump from cavitations
Answer : B

19. 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

20. The Fourneyron turbine is _________ reaction turbine.
A. An axial flow
B. An inward flow
C. An outward flow
D. A mixed flow
Answer : C

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

22. 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

23. 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

24. 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

25. 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

26. Runaway speed of a hydraulic turbine is
A. Full load speed
B. The speed at which turbine runner will be damaged
C. The speed if the turbine runner is allowed to revolve freely without load and with the wicket gates wide open
D. The speed corresponding to maximum overload permissible
Answer : C

27. The hydraulic efficiency of an impulse turbine is the
A. Ratio of the actual power produced by the turbine to the energy actually supplied by the turbine
B. Ratio of the actual work available at the turbine to the energy imparted to the wheel
C. Ratio of the work done on the wheel to the energy of the jet
D. None of the above
Answer : C

28. 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

29. In a centrifugal pump, the regulating valve is provided on the
A. Casing
B. Delivery pipe
C. Suction pipe
D. Impeller
Answer : B

30. 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

31. 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

32. 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

33. 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

34. According to fan laws, at constant weight of air or gas, the speed, capacity and pressure 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 : C

35. A centrifugal pump will start delivering liquid only when the pressure rise in the impeller is equal to the
A. Kinetic head
B. Velocity head
C. Manometric head
D. Static head
Answer : C

36. 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

37. 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

38. A double overhung Pelton wheel has
A. Two jets
B. Two runners
C. Four jets
D. Four runners
Answer : B

39. 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

40. If the ratio's of the corresponding forces acting at corresponding points 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 : C

41. 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

42. 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

43. 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

44. 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

45. The force exerted (in Newton) by a jet of water impinging normally on a fixed plate is (where w = Specific weight of water in N/m3, a = Crosssectional area of jet in m², and V = Velocity of jet in m/s)
A. waV / 2g
B. waV / g
C. waV² / 2g
D. waV² / g
Answer : D

46. 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

47. 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

48. 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

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. 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