Jane Woodard, age 11, Gleason, Tennessee, for her question:
What is a ‑dynamo?
The word dynamo is short for dynamoelectric machine. The dynamo part of the long word means power. From these scraps of word history you may think that a dynamo is a machine that makes electric power. And that is correct
The best way to explain how this dynamic machine works is to explain the first one that was ever made. This dynamo rests in the Smithsonian Institution in Washington, D.C. It is a small, simple affair, about the size of a sewing machine. Yet it can do what the biggest dynamos can do. It can produce an electric current through a wire circuit.
Strange to say, the dynamo was invented by two men, unknown to each other. One was Michael Faraday of England, the other was Joseph Henry of the United States. Both of these men had their minds on science. Both were interested in a new gadget called the electric battery. lessandro Volta had invented this electric battery and all sorts of things were being discovered about electric current.
Volta's battery was a pile of metal disks separated by layers of cloth or leather soaked in brine. i. copper wire left the battery, looped around in a circuit, and returned to the battery The cnc.uicals in the pile of disks caused electric current to flow through the wire circuit.
The Danish scientist Oersted found that a compass needle was drawn toward the electric current. The French scientist Ampere proved that an electric current produced magnetism. This last fact was of great interest to Faraday and Henry. If electric current produces magnetism, they both argued, why cannot magnetism be made to produce electric current.
The story of how Faraday solved the problem is told in great detail, He was a young student with a science problem on his mind. In his pocket he carried a magnet, some copper wire and other metalic items. Suddenly he realized that electric current was generated when copper moved through a magnetic field. Faraday rushed right home to make the first dynamo.
Its base was a horseshoe magnet. A magnetic field extends like an invisible halo around the two ends of such a magnet. Faraday fixed a copper disk to cut through this magnetic field. He joined the two ends of a copper wire circuit to his dynamo and fixed a hand crank to turn the copper disk.
It worked. When the copper disk was turned through the magnetic field, electric current flowed through the wire circuit. We do not know how or why electricity is generated when copper moves through a magnetic field. But the principle still works as well as it did in Faradays small dynamo.
The dynamos of today are usually called generators. In some, a magnetic field is swung around. and around the copper. The turning may be done by steam or water power. The result is always electric current.