Hydroelectric power is the power generated by flowing water like from running rivers. It is an attractive power source because the power generation cost is nothing. The intermediary device needed in the generation of hydroelectric power is turbine. A turbine consists of large central shaft on which a series of fan like vanes are mounted. As moving water strikes the vanes, it causes the central shaft to rotate.
How does hydro-power plants works
Hydro-power plants capture the energy of falling water to generate electricity. A turbine converts the kinetic energy of falling water into mechanical energy. Then a generator converts the mechanical energy from the turbine into electrical energy.
See below the animation, to understand the concept better.
The U.S. Army Corps of Engineers is the largest operator of hydroelectric power plants in the United States and one of the largest in the world. The 75 Corps plants have a total installed capacity of 20,474 megawatts and produce nearly 100 billion kilowatt-hours a year. USACE explains there operation as follows
“The operation of a generator is based on the principles discovered by Faraday. He found that when a magnet is moved past a conductor, it causes electricity to flow. In a large generator, electromagnets are made by circulating direct current through loops of wire wound around stacks of magnetic steel lamination. These are called field poles, and are mounted on the perimeter of the rotor.
The rotor is attached to the turbine shaft, and rotates at a fixed speed. When the rotor turns, it causes the field poles (the electromagnets) to move past the conductors mounted in the stater. This, in turn, causes electricity to flow and a voltage to develop at the generator output terminals.”
See below picture how turbine and generator work in generate electricity through workflow passed through turbine.
Working model of Hydro-power
You can buy this model from below link