Did you know that a power station can produce electricity without burning coal or oil, and without using nuclear fuel?
A power station can turn the potential energy of water into kinetic energy and then convert this energy into electrical energy by using a generator. This kind of power station is called a hydroelectric power station.

Hydroelectric power stations are usually found in mountainous areas where there is plenty of rainfall. A large dam built across a river holds back a huge lake of water. Pipes carry the water downhill to a kind of waterwheel, called a water turbine, which is connected to a generator.

There are two kinds of water turbines. Inside an impulse turbine, water flows onto the blades or paddles of a paddle-wheel and forces it to turn. In a reaction turbine, water flows out of tiny jets fixed to a wheel. As the water squirts out, the wheel turns. Water turbines thus convert the energy of moving water into electrical energy.

The water held by this dam has high potential energy. When the water rushes down to drive the turbines, the potential energy becomes kinetic energy.