| Sahiplik | Değer |
| İsim | 1-) TELEGRAPH |
| Açıklama | 1-) TELEGRAPH The telegraph is an instrument that can send messages over long distances, by electricity. It was the first great invention in modern communications. It led to the marvels of wireless radio and television. Not much more than a hundred years ago there was no good way of sending messages quickly. The American Indians used smoke signals, which were good only as far as the eye could see. Jungle tribes in Africa sent messages by beating loud drums. In Europe there were attempts to send messages across such spaces as The English Channel by flashing lights on and off. Just before the invention of the telegraph the fastest way of sending a message in The United States was the Pony Express. It took several days for a letter to cross the country, With the invention of the telegraph this could be done almost instantaneously. A) The Invention of the Telegraph An American named Samuel F. B. Morse, who was best known as a painter, was returning from Europe on a ship when he heard about Henry’s invention of the electric magnet. He had been wondering how messages could be sent by electricity, and the electromagnet gave him an idea. When he arrived in The United States, he began to work on his invention. At the same time two man in England had gotten somewhat the same idea, but the credit for the invention of the Telegraph usually goes to Morse. Morse’s idea was simple, He sent a current of electricity through a wire and when it reached the other end it magnetized a piece of iron that had been wound around with wire. The electric magnet attracted a swinging armature, which made a clicking noise as it hit an other piece of metal. Morse also tired having the free end of armature move a pencil. As the pencil moved it made marks on a piece of rolling paper under it. Opening and closing an electrical circuit controlled the messages sent over the wire when the circuit is closed. No electricity goes through the wire when the circuit is open. The operator uses a key to... |
| Dosya Adı | Bağlantı www.edubilim.com_fenbilgisi1-23-8.doc |
| Dosya Boyutu | Link |
| Dosya Tipi | doc (Mime Tipi: link) |
| Ekleyen | admin |
| Ekleme tarihi: | 21.10.2008 16:13 |
| İnceleyenler | Herkes |
| Kontrol Eden | Editor |
| İndirme sayısı | 0 İndirme sayısı |
| En son güncelleme | 14.10.2008 16:14 |
| Anasayfa | http://www.edubilim.com |
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