How does a hydroelectric dam work?

A hydroelectric dam turns the energy of moving water into electricity. The dam holds back a river to create a large reservoir, storing water at height and thereby storing potential energy. When electricity is needed, water is released and rushes down through large pipes called penstocks. The fast-moving water strikes the blades of turbines, causing them to spin, and these turbines are connected to generators that convert the spinning motion into electrical energy through electromagnetic induction. The higher the dam and the greater the water flow, the more power can be produced. Hydroelectricity is a renewable and low-carbon energy source that provides a significant share of the world electricity. However, building large dams can flood land, displace communities, and disrupt river ecosystems, so their environmental impact is an important consideration.