Which one of the following is not a source of energy?

What is the minimum speed of wind to run a windmill to maintain the necessary speed of turbine in an electric generator?

List two main advantages associated with solar cells.

Name a fraction obtained during refining of petroleum which does not find use as a fuel.

Energy can neither be created nor destroyed. Then why is there so much fuss about every crisis?

How is solar energy converted into electricity by thermal method?