# Steam and Gas Turbines Questions and Answers – Elements of Airfoil, Single Airfoil Principle and Limitations

This set of Steam and Gas Turbines Test focuses on “Elements of Airfoil, Single Airfoil Principle and Limitations”.

1. Shape of a wing or blade as seen from top view is called as airfoil.
a) True
b) False

Explanation: Shape of a wing or blade as seen from cross section is called as airfoil.

2. Airfoil can also be called as ________
a) aerofoil
b) propeller
c) sail
d) none of the mentioned

Explanation: Airfoil can also be called as Aerofoil.

3. When airfoil shape moves through fluid it produces __________
a) Thrust force
b) Drag force
c) Aerodynamic force
d) None of the mentioned

Explanation: When an airfoil shape is moved through a fluid it produces aerodynamic forces. The rest thrust and drag forces are the components of the aerodynamic force.

4. The lift to the airfoil is mainly the result of ______________
a) angle of attack
b) shape
c) angle of attack & shape
d) none of the mentioned

Explanation: The lift caused by the airfoil is primarily the result of angle of attack and shape.

5. Cambered airfoil generates lift at _________ angle of attack.
a) high
b) low
c) zero
d) none of the mentioned

Explanation: Cambered airfoil can generate lift at zero angle of attack whereas other airfoils require positive angle of attack.

6. For an airfoil fluid velocity will be ______ on upper surface when compared to lower surface.
a) higher
b) lower
c) equal
d) none of the mentioned

Explanation: As pressure is high on the upper surface than lower surface, through Bernoulli’s principle velocity is also high on the upper surface when compared to lower surface.

7. The lift force is directly proportional to _________
a) difference in the pressure between upper and lower surfaces
b) difference in the velocity between upper and lower surfaces
c) difference in the pressure & velocity between upper and lower surfaces
d) none of the mentioned

Explanation: The lift force is directly proportional to the pressure difference between the upper and lower surfaces and from Bernoulli’s principle it is also directly proportional to difference in the velocities between upper and lower surfaces.

8. Elements of airfoil are _________
a) Slats
b) Flaps
c) Slats & Flaps
d) None of the mentioned

Explanation: Basic elements of airfoil consists of slats and flaps.

9. To increase the lift at given angle of attack _______ are used.
a) Slats
b) Flaps
c) Cannot be increased
d) None of the mentioned

Explanation: Flaps are used to increase the lift at given angle of attack.

10. Increase in angle of attack can be done by ________
a) Slats
b) Governor mechanism
c) Flaps
d) None of the mentioned

Explanation: Angle of attack can be increased by slats.

Sanfoundry Global Education & Learning Series – Steam and Gas Turbines.

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