Wind Energy Multiple Choice Questions & on “Nature of Winds”.
1. What is the definition of wind?
a) Air in net motion
b) Air in motion
c) Gas molecules in random motion
d) Stationary gas molecules
Answer: a
Clarification: Wind is better defined as air in net motion. On a microscopic level, gas molecules are always in a random motion and are not visible to the naked eye. In fact, motion of individual gas molecules cannot be sensed by our senses. Thus, gas molecules are never stationary.
2. Which of the following involves studying the physics of wind flow?
a) Microbial fuel cells
b) Fluid dynamics
c) Combustion
d) Polymer science
Answer: b
Clarification: Fluid dynamics involves the studies of wind motion and its underlying physics. Fluids consists of both, liquids and gases. Hence, wind is also a fluid because it consists of gas molecules.
3. Which of the following best describes the motion of air on earth?
a) A two-dimensional vector
b) A one-dimensional vector
c) A three-dimensional vector
d) A four-dimensional vector
Answer: c
Clarification: The motion of air on earth is best described as a three-dimensional vector. It is also important to note that air motion is typically described and studied relative to earth’s rotation.
4. Which of the following are the three individual components/dimensions best used to describe air motion on earth?
a) A meridional component pointing south-to-north, a zonal component pointing north-to-east, a vertical upward component pointing from ground to sky
b) A zonal component pointing south-to-north, a meridional component pointing west-to-east and downward component pointing from sky to ground
c) A meridional component pointing north-to-south, a zonal component pointing east-to-south, a vertical upward component pointing from ground to sky
d) A meridional component pointing south-to-north, a zonal component pointing west-to-east, a vertical upward component pointing from ground to sky
Answer: d
Clarification: The three individual components that correspond to the three dimensions are – a meridional component pointing south-to-north, a zonal component pointing west-to-east and a vertical upward component pointing from ground to sky.
5. Which of the following devices indicate wind direction?
a) Weather vanes, windsocks
b) Multimeter, oscilloscope
c) Accelerometer
d) Wind’s direction cannot be measured
Answer: a
Clarification: The direction of wind is generally indicated by weather vanes, windsocks and balloons. Multimeters and oscilloscopes are electronic instruments used to measure voltage and current. Accelerometer is a device that measures a body’s acceleration.
6. What is geostrophic wind?
a) Wind generated due to disbalance between wind forces and Coriolis force
b) Wind generated due to balance between pressure gradient force and Coriolis force
c) A special wind generated from geothermal energy
d) Wind flowing in stratosphere
Answer: b
Clarification: Geostrophic wind is the wind generated due to balance between pressure gradient force and Coriolis force. It occurs above the atmospheric boundary layer (ABL).
7. What are eddies in wind?
a) Areas where the global wind blows opposite to that of the net direction of wind-motion
b) Areas where the local wind blows in the same direction as the net direction of wind-motion
c) Areas where the local wind blows opposite to that of the net direction of wind-motion
d) Areas where the local wind blows randomly to that of the net direction of wind-motion
Answer: c
Clarification: Eddies are small areas where the local wind blows opposite to that of the net direction of wind-motion for a short period of time. Eddies are always local in nature and do not occur globally.
8. The Coriolis force deflects the wind to the right in Northern Hemisphere until ______
a) equilibrium of forces is not achieved
b) gas molecules stop moving
c) water vapour evaporates
d) equilibrium of forces is achieved
Answer: d
Clarification: The Coriolis force deflects the wind to the right in Northern Hemisphere until an equilibrium is achieved. The equilibrium is between the pressure gradient of the wind and the Coriolis force.
9. Wind speed is measure by ______
a) anemometers
b) odometers
c) ammeter
d) weather vanes
Answer: a
Clarification: Anemometers are used to measure wind speeds. They are commonly used in weather stations. Odometers measure distance of a wheeled vehicle. Ammeters measure current and weather vanes are used to indicate the direction of wind.
10. What is wind speed?
a) Net molecular flux along the wind axis divided by the mean molecular number density
b) Molecular flux along the wind axis divided by the mean molecular number density
c) Net molecular flux along the wind axis divided by molecular number density
d) Molecular flux opposite the wind axis divided by the mean molecular number density
Answer: a
Clarification: Wind speed is defined as the net molecular flux along the wind axis divided by the mean molecular number density. Flux is the number of molecules crossing a unit area (square meter) in a unit time (second). Mean molecular number density is the number of molecules per cubic meter.