Hydraulics & Fluid Machineries MCQ Solved Paper for UPSC CSE

1. 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

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

3. 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

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

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

7. 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

8. 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

9. 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

10. A turbine develops 10000 kW under a head of 25 metres at 135 r.p.m. Its specific speed is
A. 175.4 r.p.m.
B. 215.5 r.p.m.
C. 241.5 r.p.m.
D. 275.4 r.p.m
Answer : C

11. 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

12. A hydraulic coupling belongs to the category of
A. Power absorbing machines
B. Power developing machines
C. Energy transfer machines
D. Energy generating machines
Answer : C

13. 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

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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

27. 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

28. 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

29. 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

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

31. 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

32. 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

33. 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

34. The specific speed of a centrifugal pump, delivering 750 litres of water per second against a head of 15 metres at 725 r.p.m., is
A. 24.8 r.p.m.
B. 48.2 r.p.m
C. 82.4 r.p.m.
D. 248 r.p.m
Answer : C

35. 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

36. 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

37. Which of the following statement is correct?
A. In an impulse turbine, the water impinges on the buckets with pressure energy.
B. In a reaction turbine, the water glides over the moving vanes with kinetic energy.
C. In an impulse turbine, the pressure of the flowing water remains unchanged and is equal to atmospheric pressure.
D. In a reaction turbine, the pressure of the flowing water increases after gliding over the vanes.
Answer : C

38. 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

39. 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

40. 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

41. Impulse turbine is generally fitted
A. At the level of tail race
B. Little above the tail race
C. Slightly below the tail race
D. About 2.5 m above the tail race to avoid cavitations.
Answer : B

42. 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

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 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

44. 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

45. In impulse Turbine, energy available at the inlet is in the form of
A. Potential Energy
B. Strain Energy
C. Kinetic energy
D. None of these
Answer : C

46. A hydraulic ram is a device used to
A. Store the energy of water
B. Increase the pressure of water
C. To lift water from deep wells
D. To lift small quantity of water to a greater height when a large quantity of water is available at a smaller height
Answer : D

47. 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

48. 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

49. 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

50. The gross or total head of the turbine is the ________ of the water levels at the head race and tail race.
A. Sum
B. Difference
C. Product
D. None of these
Answer : B