91. If a multi-jet Pelton turbine has ‘n’ number of jets, then its specific speed is directly proportional to

- n
^{0} - n
^{3/4} - n
^{1/2} - n

92. The cavitation in a hydraulic machine

- causes noise and vibration of various parts
- makes the surface rough
- reduces the discharge of a turbine
- causes sudden drop in power output and efficiency

93. The power developed by a turbine is

- directly proportional to H
^{1/2} - inversely proportional to H
^{1/2} - directly proportional to H
^{3/2} - inversely proportional to H
^{3/2}

94. In an inward flow reaction turbine

- the water flows parallel to the axis of the wheel
- the water enters at the centre of the wheel and from there flows towards the outer periphery of the wheel
- the water enters the wheel at outer periphery and then flows towards the centre of the wheel
- the flow of water is partly radial and partly axial

95. If a turbine generates 10000 kW under the head of 10 m at the speed 100 rpm, the specific speed of the turbine is

- 562.3 rpm
- 177.8 rpm
- 2056 rpm
- 1052 rpm

96. If H is the unit head, the unit power of the turbine is proportional to

- H
^{-2} - H
- H
^{-1/2} - H
^{-3/2}

97. A single jet impulse turbine of 10 MW capacity works with a head of 500 m. If the specific speed of the turbine is 10, the actual speed of the turbine is

- 236.4 rpm
- 106.9 rpm
- 392.5 rpm
- 50 rpm

98. If θ is the blade angle at the outlet, then the maximum hydraulic efficiency of an ideal impulse turbine is

- (1 – cosθ)
- (1 + cosθ)
- (1 – cosθ)/2
- (1 + cosθ)/2

99. A horizontal water jet with a velocity of 14 m/s and cross-sectional area of 10 mm^{2} strikes a flat plate held normal to the flow direction. The density of water is 1000 kg/m^{3}. The total force on the plate due to the jet would be

- 1.96 N
- Zero
- 19.6 N
- 0.196 N

100. The overall efficiency of a Pelton turbine is 70%. If the mechanical efficiency is 85%, What is its hydraulic efficiency?

- 59.5%
- 82.4%
- 72.3%
- 81.5%