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Multiple choice question for engineering

Set 1

1. Inward radial flow reaction turbine is a turbine in which water flows across the blades of runner______________
a) Radial direction
b) Radially inward
c) Radially outward
d) Axial direction

View Answer

Answer: b [Reason:] The name itself indicates that flow is in radial direction and flowing from outer periphery towards center.

2. Which of following is inward radial flow reaction turbine?
a) Pelton wheel
b) Francis turbine
c) Axial turbine
d) Kaplan turbine

View Answer

Answer: b [Reason:] Pelton is impulse a turbine, Kaplan is axial flow turbine and Francis is an inward flow reaction turbine.

3. In Inward radial flow reaction turbine which is not required?
a) Runner
b) Air tight casing
c) Guide vanes
d) Breaking jet

View Answer

Answer: d [Reason:] Here in inward flow reaction turbine, instead of jet water is passed into spiral casing directly and breaking jet is not used for its halt instead of it guide vanes are used.

4. The main difference between reaction turbine and inward radial flow reaction turbine is water flows___________
a) Radial direction
b) Radially inward
c) Radially outward
d) Axial direction

View Answer

Answer: b [Reason:] The name itself indicates the type of flow that is radial direction but the thing that is unknown is whether it is radially inward or outwards.

5. In Inward radial flow reaction turbine the ratio of tangential wheel at inlet to given velocity of jet is known as _______
a) Speed ratio
b) Flow ratio
c) Discharge
d) Radial discharge

View Answer

Answer: b [Reason:] Flow ratio is known as ratio of tangential wheel at inlet to given velocity of jet and it is scalar quantity.

6. In Inward radial flow reaction turbine the ratio of tangential velocity at inlet to the given velocity ____________
a) Speed ratio
b) Flow ratio
c) Discharge
d) Radial discharge

View Answer

Answer: a [Reason:] Speed ratio is ratio of tangential velocity at inlet to the given velocity and it is scalar quantity because it is ratio of two speeds.

7. The discharge through a reaction radial flow turbine is given by____________
a) P1*b1*Vf1
b) P2*b2*Vf2
c) P1*b2*Vf2
d) Both a & b
Where, P1= perimeter of runner at inlet, P2= perimeter of runner at outlet, b= thickness and V f= flow velocity

View Answer

Answer: d [Reason:] Discharge of radial flow reaction turbine is product of perimeter of runner, thickness, whirl velocity, at inlet as well as outlet runner vanes.

8. In Inward radial flow reaction turbine if thickness is considered then discharge is _________
a) (P1-n*t)*b1*Vf1
b) (P2-n*t)*b2*Vf2
c) (P1-n*t)*b2*Vf2
d) Both a & b
Where, P1= perimeter of runner at inlet, P2= perimeter of runner at outlet, b= width, Vf= flow velocity, n= number of blades and t= thickness of blades

View Answer

Answer: d [Reason:] Discharge of radial flow reaction turbine is product of perimeter of runner, thickness, whirl velocity, at inlet as well as outlet runner vanes. If n blades of thickness t is considered then discharge is (P1-n*t)*b1*Vf1.

9. In Inward radial flow reaction turbine if angle made by absolute velocity with its tangent is 90 degrees and component of whirl is zero at outlet is _____________
a) Radial inlet discharge
b) Radial outlet discharge
c) Flow ratio
d) Speed ratio

View Answer

Answer: b [Reason:] If angle made by absolute velocity with its tangent is 90 degrees and component of whirl is zero at outlet in radial flow reaction then total velocity will be flow velocity.

10. In which of following turbine whirl component is zero?
a) Reaction turbine
b) Inward radial flow reaction turbine
c) Axial flow turbine
d) Impulse turbine

View Answer

Answer: b [Reason:] If angle made by absolute velocity with its tangent is 90 degrees and component of whirl is zero at outlet in radial flow reaction turbines then total velocity will be flow velocity.

11. Discharge in inward flow reaction turbine ____________
a) Increases
b) Decreases
c) Remains constant
d) Gradually decreases

View Answer

Answer: b [Reason:] Discharge in inward flow reaction turbine decreases because area decreases as fluid flows across spiral structure.

12. Speed control of Outward flow reaction turbine is _________
a) Easy
b) Moderate
c) Difficult
d) Very difficult

View Answer

Answer: b [Reason:] In an outward reaction turbine, we can only partly control the speed.

13. Centrifugal head in inward flow reaction turbine __________
a) Increases
b) Decreases
c) Remains constant
d) Gradually decreases

View Answer

Answer: b [Reason:] Because centrifugal head is proportional to difference of outlet blade velocity and inlet blade velocity. Here, u2 < u1 so centrifugal head decreases.

14. Tendency of wheel to race is almost nil in ___________turbine
a) Inward flow reaction turbine
b) Outward flow reaction turbine
c) Impulse turbine
d) Axial flow turbine

View Answer

Answer: a [Reason:] In an inward reaction flow turbine, wheel moves with the constant speed.

15. Inward flow reaction turbine is used in practical applications __________
a) True
b) False

View Answer

Answer: a [Reason:]s: Inward flow reaction turbine is used in practical applications that is “Francis turbine”.

Set 2

1. The efficiency of the draft tube is ratio of ________
a) Pressure energy by kinetic energy
b) Kinetic energy by Pressure energy
c) Kinetic energy into mechanical energy
d) Pressure into mechanical

View Answer

Answer: b [Reason:] The efficiency of the draft tube is defined as the ratio of actual conversion of kinetic energy into the pressure energy. The pressure energy and kinetic energy is present at the inlet of the draft tube.

2. Draft tubes are not used in which of the following turbines?
a) Francis
b) Reaction
c) Kaplan
d) Pelton

View Answer

Answer: d [Reason:] Turbine extracts energy and converts it into useful work. Turbine is a vortex related device. Draft tubes are not used in Pelton wheels. Draft tube is a tube that is installed in power turbines.

3. The draft tube at the exit of the nozzle increases the _______
a) Temperature
b) Pressure
c) Volume of the flow
d) Density of flow

View Answer

Answer: b [Reason:] The draft tube at the exit of the nozzle increases the pressure in the fluid. It increases it at the expense of its velocity. This means that the turbine can reduce its pressure without fear of back flow to the tail race.

4. Efficiency of a draft tube gives __________
a) Temperature difference
b) Pressure difference
c) Kinetic energy difference
d) Density of flow

View Answer

Answer: c [Reason:] The efficiency of the draft tube gives difference of the kinetic energy between the inlet and the outlet tube losses. The efficiency of the draft tube is defined as the ratio of actual conversion of kinetic energy into the pressure energy.

5. Cavitation in a draft tube occurs when _______
a) Temperature difference
b) Pressure drop
c) Kinetic energy difference
d) Density of flow

View Answer

Answer: b [Reason:] Cavitation in a draft tube occurs when pressure drop takes place. The absolute pressure falls below the saturated vapour pressure of the water for the given temperature.

6. Which among the following is an important parameter to avoid cavitation?
a) Tail race length
b) Head race length
c) Height of draft tube
d) Pump

View Answer

Answer: c [Reason:] Cavitation in a draft tube occurs when pressure drop takes place. The absolute pressure falls below the saturated vapour pressure of the water for the given temperature. Height of the draft tube is an important parameter to avoid cavitation.

7. The draft tube is situated in the _______
a) Inlet
b) Outlet
c) Tank
d) Nozzle

View Answer

Answer: b [Reason:] The simple elbow draft tube is placed close to the inlet of the turbine. It consists of an extended elbow type tube. It is mainly used in the Kaplan turbine. It is placed close to the tail race of the turbine.

8. Which equation is applied to determine the flow?
a) Newtons equation
b) Rutherford’s equation
c) Bernoulli’s equation
d) Faradays equation

View Answer

Answer: c [Reason:] Bernoulli’s equation is used to determine the flow of the fluid from inlet to the outlet. It also helps in avoiding cavitation. Cavitation in a draft tube occurs when pressure drop takes place.

9. Height of the draft tube is denoted by _____
a) H
b) h
c) z
d) x

View Answer

Answer: c [Reason:] Height of the draft tube is denoted by ‘z’. It is equated to z2, which is attached at the outlet of the turbine. Thus, the universal symbol to denote height of the draft tube is ‘z’.

10. Draft tube allows turbine to be placed above the tail race.
a) True
b) False

View Answer

Answer: a [Reason:] The draft tube helps to cut down the cost of excavation. The draft tube is placed close to the tail race. The turbine pressure head is increased by decreasing the velocity at the draft tube. Draft tube allows turbine to be placed above the tail race.

Set 3

1. Hydraulic energy is converted into another form of energy by hydraulic machines. What form of energy is that?
a) Mechanical Energy
b) Electrical Energy
c) Nuclear Energy
d) Elastic Energy

View Answer

Answer: a [Reason:] Hydraulic machines firstly convert the energy possessed by water into mechanical energy. Later it can be transformed into electrical energy.

2. In hydraulic turbines, inlet energy is greater than the outlet energy.
a) True
b) False

View Answer

Answer: a [Reason:] The operating member which receives energy at the inlet should be more compared to energy at the outlet.

3. Which principle is used in Hydraulic Turbines?
a) Faraday law
b) Newton’s second law
c) Charles law
d) Braggs law

View Answer

Answer: b [Reason:] A Hydraulic Machine uses the principle of momentum which states that a force is generated which is utilized in a turbine.

4. Buckets and blades used in a turbine are used to:
a) Alter the direction of water
b) Switch off the turbine
c) To regulate the wind speed
d) To regenerate the power

View Answer

Answer: a [Reason:] Turbines use blades and buckets to alter the direction of water. It is used to change the momentum of water. As momentum changes, force is produced to rotate the shaft of a hydraulic machine.

5. _______________is the electric power obtained from the energy of the water.
a) Roto dynamic power
b) Thermal power
c) Nuclear power
d) Hydroelectric power

View Answer

Answer: d [Reason:] The energy from the energy of water is also called hydro power. The electric power so obtained is known as hydroelectric power.

6. Which energy generated in a turbine is used to run electric power generator linked to the turbine shaft?
a) Mechanical Energy
b) Potential Energy
c) Elastic Energy
d) Kinetic Energy

View Answer

Answer: a [Reason:] The kinetic and potential energies produced are converted to some useful mechanical energy. This part of energy is available to the turbine shaft.

7. Hydraulic Machines fall under the category :
a) Pulverizers
b) Kinetic machinery
c) Condensers
d) Roto-dynamic machinery

View Answer

Answer: d [Reason:] Hydraulic Machines use the principle of rotation of blades to alter the speed of water. Hence fall under roto dynamic machinery.

8. Which kind of turbines changes the pressure of the water entered through it?
a) Reaction turbines
b) Impulse turbines
c) Reactive turbines
d) Kinetic turbines

View Answer

Answer: a [Reason:] Reaction turbines which act on water try to change the pressure of the water through its motion.

9. Which type of turbine is used to change the velocity of the water through its flow?
a) Kinetic turbines
b) Axial flow turbines
c) Impulse turbines
d) Reaction turbines

View Answer

Answer: c [Reason:] In Impulse turbines, potential energy is utilized to convert as kinetic energy thereby changing the velocity of the water through its process.

10. Which type of turbine is a Francis Turbine?
a) Impulse Turbine
b) Screw Turbine
c) Reaction turbine
d) Turgo turbine

View Answer

Answer: c [Reason:] Francis turbine is a reaction turbine as it changes the pressure of water through its process. Hence it cannot be an impulse turbine.

11. How many types of Reaction turbines are there?
a) 5
b) 4
c) 3
d) 9

View Answer

Answer: a [Reason:] There are five types of reaction turbines namely VLH, Francis, Kaplan, Tyson, Gorolov helical turbine.

12. Turgo Turbine is an impulsive turbine.
a) True
b) False

View Answer

Answer: a [Reason:] In a turgo turbine, velocity of water changes with due respect. Hence it is an Impulse turbine.

13. Which kind of turbine is a Fourneyron Turbine?
a) Inward flow turbine
b) Outward flow turbine
c) Mixed flow turbine
d) Radial flow turbine

View Answer

Answer: b [Reason:] In a Fourneyron turbine, the flow is centrifugal type. The flow is outwards from the centre to the periphery.

Set 4

1. Draft tube is also called_______
a) Straight divergent tube
b) Simple elbow tube
c) Thermal tube
d) Elbow tube with varying cross section

View Answer

Answer: a [Reason:] Draft tube is one of the most commonly used in the Kaplan turbine. It works as an outlet at the Kaplan turbine. Draft tube is also called straight divergent tube.

2. A draft tube helps in converting kinetic energy into________
a) Electrical work
b) Mechanical work
c) Chemical work
d) Thermal work

View Answer

Answer: b [Reason:] Turbine extracts energy and converts it into useful work. Turbine is a vortex related device. It means turbulence. Steam turbine converts energy into mechanical work by extracting thermal energy from pressurized steam.

3. Most common application of the draft tube is ______
a) Rotor
b) Motor
c) Pump
d) Filter

View Answer

Answer: c [Reason:] Most common application of the draft tube is different types of pumps. It plays an important role in the putlet of the pump and the turbine.

4. Draft tube consists of conical diffuser with angles of______
a) 10 deg
b) 20 deg
c) 30 deg
d) 40 deg

View Answer

Answer: a [Reason:] Draft tube consists of conical diffuser with angles of 10 degrees with respect to its position, Draft tubes are situated in the outlet of the turbine.

5. What is the purpose of a Draft tube?
a) To prevent flow separation
b) To avoid Pressure drag
c) To prevent rejection of heat
d) To increase efficiency

View Answer

Answer: a [Reason:] Draft tube in a turbine and pumps helps to prevent flow separation in order to increase the turbine efficiency and increase its performance.

6. What is the maximum value of efficiency in a draft tube?
a) 100
b) 50
c) 90
d) 40

View Answer

Answer: c [Reason:] The maximum value of efficiency in a draft tube is 90 percent. It cannot exceed more than 90 percent because of the heat losses due to flow of fluid.

7. The simple elbow draft tube is placed close to the_______
a) Head race
b) Tail race
c) Tank
d) Nozzle

View Answer

Answer: b [Reason:] The simple elbow draft tube is placed close to the tail race. It consists of an extended elbow type tube. It is mainly used in the Kaplan turbine. It is placed close to the tail race of the turbine.

8. Turbine that consists of draft tubes is called as__________
a) Impulse turbine
b) Curtis turbine
c) Rateau turbine
d) Reaction turbine

View Answer

Answer: d [Reason:] A turbine that consists of draft tubes is called as a reaction turbine. Reaction turbines make maximum use of the draft tubes for improving its performance characteristics.

9. Which of the following is a 50 percent reaction turbine?
a) Parsons turbine
b) Curtis turbine
c) Rateau turbine
d) Pelton wheel

View Answer

Answer: a [Reason:] A turbine that consists of moving nozzles which are alternating with the fixed nozzles is called as a reaction turbine. When the steam hits the nozzle, the pressure is decreased and the temperature is increased. It is also called as Parson’s turbine.

10. The simple elbow draft tube helps to cut down the cost of excavation.
a) True
b) False

View Answer

Answer: a [Reason:] The simple elbow draft tube helps to cut down the cost of excavation. The simple elbow draft tube is placed close to the tail race. It consists of an extended elbow type tube. It is mainly used in the Kaplan turbine. It is placed close to the tail race of the turbine.

11. The exit diameter for a simple elbow draft tube should be________
a) Large
b) Small
c) Very small
d) Same

View Answer

Answer: a [Reason:] The exit diameter for a simple elbow draft tube should be large as possible. It helps to cut down the cutdown the cost and recover the kinetic energy at the outlet of runner. The simple elbow draft tube is placed close to the tail race.

12. Properties that do not affect a draft tube is _______
a) Pressure
b) Temperature
c) Pressure velocity
d) Velocity

View Answer

Answer: b [Reason:] Temperature does not affect the performance of the draft tube. With increase and decrease of temperature of fluid in a draft tube, the draft tube remains the same.

13. The other name for elbow with varying cross section tube is called_____
a) Pressure tube
b) Bent draft tube
c) Velocity tube
d) Sink tube

View Answer

Answer: b [Reason:] The other name for elbow with varying cross section tube is called bent draft tube. It is so called because only the bent part is of varying cross section. Thus, the answer is bent draft tube.

14. What is the efficiency of the simple elbow type draft tube?
a) 10
b) 30
c) 60
d) 90

View Answer

Answer: c [Reason:] The efficiency of the simple elbow type draft tube is 60 percent. The exit diameter for a simple elbow draft tube should be large as possible. It helps to cut down the cutdown the cost and recover the kinetic energy at the outlet of runner. The simple elbow draft tube is placed close to the tail race.

15. The horizontal portion of the draft tube is usually bent to prevent entry of air from the exit end.
a) True
b) False

View Answer

Answer: a [Reason:] The horizontal portion of the draft tube is usually bent to prevent entry of air from the exit end. This might lead to a mixing up of gases. In order to avoid this, it is important to avoid air entry from exit.

Set 5

1. Francis turbine is typically used for which of the following values of available heads?
a) 300 m
b) 100 m
c) 30 m
d) 5 m

View Answer

Answer: b [Reason:] Francis Turbine is a medium head turbine, typically used for heads in the range 60 m to 240 m. Hence, only 100 m from the above options fit in that range.

2. Water flow velocity is given 10 m/s. The runner diameter is 3 m and the width of the wheel is 25 cm. Find the mass of water (kg) flowing across the runner per second.
a) 7500π
b) 50π
c) 300π
d) RPM of the turbine needs to be given

View Answer

Answer: a [Reason:] Area of the flow (A) = πDB = 0.75π m2. Mass flow rate = ρ.A.Vf = 1000*0.75π*10 = 7500π kg/s.

3. Work done per second by a Francis turbine can be given by ρAVf (Vw1u1 + Vw2u2).
a) True
b) False

View Answer

Answer: b [Reason:] The work done per second is given by ρAVf (Vw1u1 – Vw2u2). Hence, the outlet term is subtracted from the inlet term and not added to it.

4. Which of the following terms is considered to be zero while deriving the equation for work done per second for Francis Turbine?
a) Vr1
b) Vw2
c) Vf2
d) Vr2

View Answer

Answer: b [Reason:] Since the flow out of the runner of the Francis turbine is axial in nature, the whirl velocity at outlet is zero. Hence, Vw2 is ignored in the derivation of work done for Francis Turbine.

5. Power developed by Francis turbine are calculated for a certain set of conditions. Now, the inlet whirl velocity is doubled, the blade velocity at inlet is doubled and the flow velocity is quartered. The power developed:
a) Is 4 times the original value
b) Is 2 times the original value
c) Is ½ times the original value
d) Is same as the original value

View Answer

Answer: d [Reason:] The power developed by a Francis Turbine is given by P = ρAV (Vw1.u1). Hence, if inlet whirl velocity is doubled, the blade velocity at inlet is doubled and the flow velocity is quartered, then the power developed will remain the same as its original value.

6. Volume flow rate of water in a Francis turbine runner is 25 m3/s. The flow velocity, whirl velocity and blade velocity are 11 m/s, 10 m/s and 5 m/s respectively, all values given at runner inlet. Find the power developed by the turbine.
a) 25 kW
b) 1.25 MW
c) 1.25 kW
d) 25 MW

View Answer

Answer: b [Reason:] P = ρQ (Vw1.u1te is directly given.

7. The flow rate of the water flow in a Francis turbine is increased by 50% keeping all the other parameters same. The work done by the turbine changes by?
a) 50% increase
b) 25% increase
c) 100% increase
d) 150% increase

View Answer

Answer: a [Reason:] The Power developed in a Francis turbine directly depends on the flow rate of water. If flow rate is increased by 50%, i.e. made 1.5 times the original value, then the power developed becomes 1.5 times its original value too. Hence, a 50% increase.

8. A student performs an experiment with a Francis turbine. He accidently set the RPM of Francis turbine to 1400 rpm instead of 700 rpm. He reported the power to be 1 MW. His teacher asks him to perform the same experiment using the correct RPM. The student performs the same experiment again, but this time the erroneously doubled the flow velocity. What does the student report the power to be?
a) 0.5 MW
b) 0.25 MW
c) 2 MW
d) 1 MW

View Answer

Answer: d [Reason:] The Power developed by the turbine varies directly with both flow velocity as well as the blade velocity (which in turn varies directly with RPM). So, if all parameters were correct, the reported value should be 0.5 MW. But, flow velocity is again doubled, so the student again reports 1 MW.

9. Velocity of whirl at the runner inlet is given to be 10 m/s and blade velocity to be 5 m/s. The volume flow rate of water in Francis turbine is given to be 25 m3/s. Find the power generated by the turbine?
a) 1700 HP
b) 800 HP
c) 3400 HP
d) 1000 HP

View Answer

Answer: a [Reason:] P = ρQ (Vw1.u1) = 1.25 MW. It is important to know the 1 HP = 736 W. Hence, the answer is 1.25 MW/ 736 = 1700 HP.

10. The available head of a Francis Turbine is 100 m. Velocity of the flow at the runner inlet is 15 m/s. Find the flow ratio.
a) 0.33
b) 0.45
c) 0.67
d) 0.89

View Answer

Answer: a [Reason:] Flow ratio is given by ψ = Vf1 / sqrt(2gH). Substituting the given values and taking the value of g = 10 m/s2, we get ψ = 0.33.

11. How does the flow ratio (ψ) of a Francis turbine vary with available head (H)?
a) ψ α H
b) ψ α 1/H
c) ψ α sqrt (H)
d) ψ α 1/(sqrt (H))

View Answer

Answer: d [Reason:] Flow ratio is given by ψ = Vf1 / sqrt(2gH). Hence, the flow ratio is inversely proportional to the square root of available head.

12. What is the typical value for flow ratio in a Francis turbine?
a) 0.05 – 0.1
b) 0.15 – 0.30
c) 0.35 – 0.45
d) 0.50 – 0.60

View Answer

Answer: b [Reason:] Flow ratio denoted by ψ is given by Vf1 / sqrt(2gH). Sqrt (2gH) is called the spouting velocity. The practical values of the flow ratio for Francis turbine lie in the range of 0.15 – 0.3.

13. The available head of a Francis Turbine is 120 m. The blade velocity is given 35 m/s. Find the speed ratio of the turbine.
a) 0.56
b) 0.61
c) 0.71
d) 0.81

View Answer

Answer: c [Reason:] The speed ratio φ = U/ sqrt(2gH). Hence, substituting the given values into this equation, we get φ = 0.71.

14. The speed ratio (φ) varies directly with which of the following parameters?
a) Vw1
b) V1
c) N (RPM)
d) H (Available head)

View Answer

Answer: c [Reason:] The speed ratio is given by φ = U/ sqrt(2gH). Speed ratio directly depends upon U which in turn depends directly upon RPM of the turbine (N).

15. The typical value range of speed ratio for a Francis turbine is:
a) 0.3 – 0.6
b) 0.5 – 0.6
c) 0.1 – 0.4
d) 0.6 – 0.9

View Answer

Answer: d [Reason:] Speed ratio denoted by φ is given by U / sqrt(2gH). Sqrt (2gH) is called the spouting velocity. The practical values of the speed ratio for Francis turbine lie in the range of 0.6 – 0.9.