The correct answer is (c) depends on wind velocity.
Explanation:
Windmills generate power by converting the kinetic energy of the wind into mechanical energy, which is then often converted to electricity. The amount of kinetic energy in the wind is directly proportional to the wind speed cubed. Therefore, a higher wind velocity results in significantly more power generated by a windmill.
Why other options are incorrect:
(a) is more in rainy season since damp air would mean more air mass hitting the blades:
While damp air might have a slightly higher density, the primary factor influencing power generation is wind velocity, not just air mass. The difference in density due to humidity is negligible compared to the impact of wind speed. Additionally, increased precipitation can actually hinder wind turbine efficiency by causing blade icing.
(b) depends on the height of the tower:
The height of the tower does play a role in wind power generation, as it allows the blades to access higher wind speeds at higher altitudes. However, the dependence on height is not as direct as the relationship with wind velocity. Wind speed is the dominant factor. For example, a shorter tower in a high-wind area could generate more power than a taller tower in a low-wind area.
(d) can be increased by planting tall trees close to the tower:
Planting tall trees near a wind turbine would actually decrease its power generation. Trees act as windbreaks, disrupting the airflow and reducing the wind speed reaching the turbine blades. This is the opposite of what is desired. Wind farms are strategically placed in open areas with unobstructed wind access.