|How do windmills work to generate electricity? — KT, Aurora, Ontario
Windmills extract energy from the wind by rotating as the wind twists them. Whenever an object rotates in the same direction as the torque (the twist) being exerted on it, mechanical work is done on that object. In this case, wind exerts a torque on the windmill's blades and they rotating in the direction of that torque, so the wind is doing work on the blades. Work is the mechanical transfer of energy, so the wind is transferring some of its energy to the blades.
The blades don't keep this newly acquired energy. Instead, they do work on a generator. The generator, which consists of a rotating magnet that spins within stationary coils of wire, uses this energy to generate electricity. The amount of power that a windmill generates depends on the wind speed and the windmill's size, but large windmills can generate in excess of a million watts of electric power.