Hydroelectric energy is generated by building dams that force moving water to turn machinery like turbines connected to generators. This converts the kinetic energy of the flowing water into electrical energy. While hydroelectricity is a renewable source that doesn't pollute, building large dams can be very expensive and damage wildlife habitats by flooding land. However, small-scale experiments show how kinetic energy from moving water can be used to light a bulb by powering a small turbine connected to a dynamo.