Hydraulics & Fluid Machineries 1000+ MCQ with answer for RBI Assistant

1. 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

2. 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

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

4. 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

5. 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

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

7. 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

8. 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

9. Motion of a liquid in a volute casing of a centrifugal pump is an example of
A. Rotational flow
B. Radial
C. Forced spiral vortex flow
D. Spiral vortex flow
Answer : D

10. 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

11. 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

12. 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

13. The jet ratio is defined as the ratio of the
A. Diameter of jet to the diameter of Pelton wheel
B. Velocity of jet to the velocity of Pelton wheel
C. Diameter of Pelton wheel to the diameter of jet
D. Velocity of Pelton wheel to the velocity of jet
Answer : C

14. 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

15. 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

16. Hydraulic accumulator is used for
A. Accumulating oil
B. Supplying large quantities of oil for very short duration
C. Generally high pressures to operate hydraulic machines
D. Supplying energy when main supply fails
Answer : D

17. 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

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

19. The power produced by the reaction turbine is ________ to the head of water.
A. Directly proportional
B. Inversely proportional
C. 4th power
D. None of these
Answer : A

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

21. A hydraulic accumulator 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 : B

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 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

24. 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

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

26. 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

27. 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

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. 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

30. 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

31. 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

32. 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

33. 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

34. 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

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. 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

37. 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

38. 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

39. 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

40. 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

41. 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

42. 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

43. 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

44. 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

45. 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

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. The mechanical efficiency of an impulse turbine is
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 : B

48. Which of the following pump is generally used to pump highly viscous fluid?
A. Centrifugal pump
B. Reciprocating pump
C. Air lift pump
D. Screw pump
Answer : D

49. The cavitation in a hydraulic machine
A. Causes noise and vibration of various parts
B. Reduces the discharge of a turbine
C. Causes sudden drop in power output and efficiency
D. All of the above
Answer : D

50. The speed of an imaginary turbine, identical with the given turbine, which will develop a unit power under a unit head, is known as
A. Normal speed
B. Unit speed
C. Specific speed
D. None of these
Answer : C