The electricity produced from flowing water is called Hydroelectric power. The world's first hydroelectric power plant was set up in 1882 in Wisconsin USA. It had a very small output, supplying power only for about 250 light bulbs. But from this small start the production of hydroelectricity has grown steadily, and today 6% of the world's need is met with hydroelectricity.
Water from a river is directed to the site of the power plant. A high barrier or dam is constructed to hold back the water. This raises the height of the water level. On the other side of the dam a sharp fall of several meters is constructed so that the water flowing from the gates of the dam-falls from this height. The falling water rotates big water turbines. A turbine is connected to the shaft of a generator whose armature rotates between the poles of a strong magnet that produces electricity.
Modern water turbines use curved internal blades and the water flows at high speed through pipes rather than the open channel.
