How much electric power can a big dam generate?
For countless ages the rivers and waterfalls squandered their mighty energy in an endless dash to the sea. The invisible might of electricity was untamed. Then about a century ago these two forceful giants were harnessed in humming generators to yield hydroelectric power. Michael Faraday sat in class, but his mind was not entirely on the lecture. He was toying with a magnet and some bits of copper and dreaming of a great idea. He knew that magnetism and electricity were related, and he suspected that the two could be wedded to generate electric current then suddenly he saw how to do it. Later he made a small gadget, the first electric dynamo, to test his idea. Faraday’s dynamo was a horseshoe magnet with a copper disk set at right angles to turn through its open end. He fixed the two ends of a wire loop to the gadget and turned the disk with a handcrank. The disk cut through the invisible lines of force surrounding the magnet and this generated electric current through the wire circuit
