64. If D is the diameter of Pelton wheel and d is the diameter of the jet, then number of buckets on periphery of a Pelton wheel is equal to

A.D/2d

B.(D/2d)+10

C.(D/2d)+15

D.(D/2d)+20

65. Impulse turbine is used for

A.Low head

B.High head

C.Medium head

D.High flow

66. For maximum efficiency, the speed of a pelton wheel as compared to the speed of the water jet is

A.Same

B.Half

C.Thrice

D.Four times

67. If α is the angle of blade tip at outlet, then maximum hydraulic efficiency of an Impulse turbine is

A.(1+cos α)/ 2

B.(1-cos α)/ 2

C.(1-sin α)/ 2

D.(1+sin α)/ 2

68. In reaction turbine

A.Kinetic energy is appreciable as the fluid leaves the runner and enters draft tube

B.It is not exposed to atmosphere

C.Total energy of fluid is converted to kinetic energy in the runner

D.It is exposed to atmosphere

69. If α is the angle subtended by two adjacent buckets in a pelton wheel, then the no. of buckets is equal to

A.40/α

B.180/α

C.270/α

D.360/α

70. In reaction turbine, draft tube is used

A.To transport water downstream without eddies

B.To convert the kinetic energy to flow energy by a gradual expansion of the flow cross-section

C.For safety of turbine

D.To increase flow rate

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