A wind turbine is a modern, scientifically designed version of a windmill. Its gently turning blades, which rotate to face the wind, are connected to a gearbox. The gearbox turns a generator at the much higher speed needed for the efficient generation of electricity.

One kind of generator is called an alternator. It produces alternating current – electric current that continually reverses its direction of flow. The alternator has coils of wire mounted on a spindle that turns inside a magnet (usually an electromagnet). The part that turns is called the rotor. As the rotor turns, its wires cut through the field of the magnet. This generates a voltage that drives current through the bulb.

By the time the rotor has gone through half a turn, the direction in which the wires are moving through the field has reversed. This means that the voltage across the wires is reversed, and so is the current through the light bulb. This is how the alternator produces alternating current. Most generators are alternators, because alternating current can be used with transformers to change the voltage of an electricity supply.

It takes 300 wind turbines to match the power of one generator in a power station. This is why they are usually grouped together in large numbers on wind farms. Wind farms take up a lot of space, so in future they may be built out at sea. As winds are powered by the Sun, they will still be blowing and providing energy when fossil fuels, such as coal and oil, have run out. Using wind power also cuts pollution from burning these fuels, and avoids the dangers of nuclear power.