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Even a child's toy windmill is a simple form of turbine.
Since the blades of a wind turbine are rotating, they must have kinetic energy, which they "steal" from the wind.
Now it's a basic law of physics (known as the conservation of energy) that you can't make energy out of nothing, so the wind must actually slow down slightly when it passes around a wind turbine.
The longer the rotor blades, the more energy they can capture from the wind.
The giant blades (typically 70m or 230 feet in diameter, which is about 30 times the wingspan of an eagle) multiply the wind's force like a wheel and axle, so a gentle breeze is often enough to make the blades turn around.
In practice, wind turbines use different types of generators that aren't very much like dynamos at all.
(You can read about how they work, more generally, in our main article about generators.) If you've ever stood beneath a large wind turbine, you'll know that they are absolutely gigantic and mounted on incredibly high towers.The wind loses some of its kinetic energy (energy of movement) and the turbine gains just as much.As you might expect, the amount of energy that a turbine makes is proportional to the area that its rotor blades sweep out; in other words, the longer the rotor blades, the more energy a turbine will generate.Wind turbines are analogous: like cars, they're designed to work efficiently at a range of different speeds.A typical wind turbine nacelle is 85 meters (280 feet) off the ground—that's like 50 tall adults standing on one another's shoulders! If you've ever stood on a hill that's the tallest point for miles around, you'll know that wind travels much faster when it's clear of the buildings, trees, hills, and other obstructions at ground level.Obviously, faster winds help too: if the wind blows twice as quickly, there's potentially eight times more energy available for a turbine to harvest.That's because the energy in wind is proportional to the cube of its speed.Even so, typical wind turbines stand idle about 14 percent of the time, and most of the time they don't generate maximum power.This is not a drawback, however, but a deliberate feature of their design that allows them to work very efficiently in ever-changing winds. Cars don't drive around at top speed all the time: a car's engine and gearbox power the wheels as quickly or slowly as we need to go according to the speed of the traffic.When you ride a bicycle, the dynamo touching the back wheel spins around and generates enough electricity to make a lamp light up.The same thing happens in a wind turbine, only the "dynamo" generator is driven by the turbine's rotor blades instead of by a bicycle wheel, and the "lamp" is a light in someone's home miles away.