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Electricity and Communications Electricity and Communications SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 1 Electricity z Every aspect of modern industrialized world is dependent on a steady supply of electricity. z All modern communications equipment runs on electricity, as do all computers. z Electricity is the all-purpose form of energy that runs lighting systems and most appliances. z Electricity is the medium of choice for transporting and transmitting energy from many other sources. SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 2 History of Electricity z Electricity began to be studied and understood around the beginning of the Industrial Revolution. z Benjamin Franklin determined that the two “kinds” of electric charge known, positive and negative, cancel each other when brought together. They were merely polarities of the same thing. z He also established that lightning is electricity, with his famous kite experiment. SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 3 1 The Electric Battery z In 1800, Alessandro Volta found a way to store electricity by making a pile of alternating copper and zinc plates, separated by cardboard soaked in acid. This was the first electric battery. SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 4 Electricity and Magnetism z In the 19th century, scientists discovered the link between electricity and magnetism: z A changing electric current produces a magnetic attraction, and a moving magnet produces an electric current. z Any form of energy can be used to move (e.g. spin) a magnet, which will make electricity. That electricity can then be used to cause motion elsewhere. SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 5 Signalling z One of the first practical uses of electricity was to improve the technology of long distance communication. z Until electricity was used to send messages, communication was limited first by the distance that sound will travel and be recognizable and, given a coding system, by the distance that can be seen and interpreted. z At right, a 1792 French semaphore station. SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 6 2 The Idea of the Telegraph z In the 1830s experiments were made in sending signals by turning an electric current on and off on in connecting wires. This produced a magnetic field that would disturb a magnet at the other end of the wire. z At right, the Cooke & Wheatstone 5-needle telegraph. SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 7 Morse Code and the Telegraph z In the 1840s, Samuel Morse invented a code that represented each letter of the alphabet as a combination of short and longer signals, which could be represented by turning an electric current on and off quickly again and again. z This used a single wire, instead of 5 or more in previous inventions. SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 8 The Telegraph takes off z By 1850 every state of the US east of the Mississippi was on the telegraph network. z The main first users were the railroads, that needed timely information about train traffic. z Next was commerce. z Downtown New York was crisscrossed in no time with telegraph wires on poles. SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 9 3 Telegraph lines unite the Industrialized World z By 1861, a telegram could be sent across North America, from New York to San Francisco. z By 1866 there were already two undersea cables crossing the Atlantic Ocean. SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 10 Speaking on the Telegraph z Alexander Graham Bell, a teacher of deaf children, tried to invent a device that would make recognizable electric signals that could be interpreted by the deaf children. z He found a way to convert ordinary sound into electric impulses at varying frequencies and then use the electricity to vibrate a magnet that would emit sound waves. SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 11 The Telephone Alexander Graham Bell inaugurating the first New York to Chicago telephone line. SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 12 4 The Telephone Network z First used in businesses as a point to point communication device where frequent distance communication was necessary. E.g. into mines, from warehouse to head office. z Later, the idea of a network of phone lines that could call any of each other developed. z These required a central exchange. z The picture is of a 19th century switchboard, probably from a large business with phones in different departments and locations. SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 13 Making the Telephone a Commodity z Like many technological facets of modern society that provided a new range of services, the first customers were those who immediately perceived the telephone’s value for their current needs. z It inevitably took longer for a wider public to be convinced that the new gadget was something they would view as a necessity once they had it. z This required advertising. z The telephone was one of the first modern-day inventions that was promoted with display ads in newspapers and magazines by the Bell Telephone company. SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 14 An Ad for the Bell Telephone of 1877. SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 15 5 The Telegraph blazes the trail for the Telephone z The telephone had its first successes where the telegraph was already well established, namely the United States and Canada. z The telegraph lines were already in heavy use to compensate for the relatively long distances between cities and towns in North America, and because of the prominence of the railroads. z The telegraph lines could easily be adapted to telephone usage. z (Of course, Bell was from Canada and the United States.) SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 16 The Spread of Telephones z In the industrialized nations, the telephone spread quickly. z In the U.S., The number of telephones doubled every four years between 1880 and 1900, from 48,000 to 1,350,000. z In Europe, the pace was slower, perhaps because, unlike North America, the phone service was run by the post offices. z In 1911, the ratio of telephones to people in the US was 1 to 20. In Britain and Germany, it was 1 to 100. z Elsewhere it was much lower. SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 17 Telephones Everywhere z Telephones are now universal in the industrialized nations. z In countries that never did get universal landline service, cell phones have an even greater rate of growth than in some industrialized nations. z Instead of laying down the expensive infrastructure of land lines, these countries have put their capital into wireless transmitters. SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 18 6 Modern society impossible without the telephone? z A quote from Robert Bruce’s biography of Alexander Graham Bell: z “Without the telephone as its nervous system, the twentieth-century metropolis would have been stunted by congestion and slowed to the primordial pace of messengers and postmen. And the modern industrial age would have been born with cerebral palsy.” SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 19 Electric Lighting z Like the bicycle preceding the automobile and the telegraph preceding the telephone, each created a demand for a service that was provided better by the following technology. z For artificial lighting, the oil lamp created a demand for night lighting, that gas lighting built upon. z If electricity could be used to make a better light, there was a ready market to exploit. z Enter the inventor…. SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 20 Thomas Alva Edison z One of the world’s first professional inventors. z Lodged 1093 patents. z Edison created many gadgets that used the power of electricity: z The phonograph. z The motion-picture camera. z The stock ticker. z The repeating telegraph. z Edison began the practice of answering the phone with “hello.” SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 21 7 The electric light bulb z Electricity, forced through a poor conductor, gives off a glow. z It also produces heat, generally enough to set the glowing object on fire. z But if the electrified object has no oxygen around it, it cannot burn, and therefore will just continue to glow. z Edison placed a filament—a poor electrical conductor—inside a container emptied of air, and forced electricity through it. z After many unsuccessful attempts, he and his helpers found a combination that worked. SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 22 Street lighting by electricity z Gas and oil street lights were already common. z Edison organized an extravagant display of the potential of electric street lighting in his home town of Menlo Park, New Jersey on December 31, 1879, attended by dignitaries brought in by a special train. z It worked, and it did not take long before there was a steady demand for electric lighting. SC/NATS 1840, Science and the Environment – XVI Electricity & Communications 23 Electric power everywhere z Edison realized that to sell his invention of the light bulb, there had to be a supply of electricity readily available. z So he also developed the concept of the electric power generating station, and the beginning of the power grid that crisscrosses all industrialized communities.
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