The History of Electrical Currents
Electrical currents are formed from charged particles that move from one location to another, so that they flow. There are two types, DC and AC.
Direct currents (DC) flow in one direction only, and may appear as a straight line. Alternating currents (AC) flow first in one direction and then the other. Their appearance is that of a sinusoidal wave, and they vary in time. Sinusoidal waves are curvy or pulsating and have patterns that repeat, such as sine and cosine waves.
The early history of electrical currents involves breakthroughs made in electricity, and electromagnetism.
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Electricity
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The ancient Greeks discovered that when amber was rubbed by cloth, it attracted materials such as leaves and dust. Electricity comes from the word electron, which is the Greek word for amber. William Gibson, an English physician to Queen Elizabeth I, coined the term. The type of electricity the Greeks observed by rubbing an object and thereby charging it is called static electricity.
Benjamin Franklin was the first to name the two types of charges, calling one positive and the other negative. Franklin also discovered that lightning is electricity, by performing an experiment with a kite.
A discovery by Italian physicist Luigi Galvani in the 1780s led to a very important invention. Galvani found that when he used two different metals as he was dissecting a frog's leg, it twitched. In 1800, fellow countryman and physicist Alessandro Volta improved on Galvani's findings, and invented the battery. Volta took several discs of zinc and silver, and placed cloth or paper that had been soaked in brine or acid between them.
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Electromagnetism
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Hans Christian Oersted, a Danish physicist, discovered the connection between electricity and magnetism in 1820. He found that a compass needle is deflected when it is placed near a current-carrying wire connected to a battery. Oersted also observed that a magnet exerts a force on a current-carrying wire when it is placed near it.
Andre Marie Ampere, a physicist from France, built on Oersted's discovery. He found the relationship between current in a wire of any shape to that of a magnetic field around it.
In 1831, the Englishman Michael Faraday found that a loop of wire moving in a magnetic field produced a current. This process is called electromagnetic induction. Faraday constructed the first electric motor and dynamo, as a generator was called then.
Thomas Edison
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Thomas Edison was an American inventor who revolutionized the use of direct current, which was the only current in use back then. Among the many inventions he made while using it are the phonograph, the first practical light bulb, and the motion picture camera. Edison's company built one of the first power plants, and became the world's main builder of direct current systems.
Nikola Tesla
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Nikola Tesla was a Croatian who in later years became an American citizen. He built the first AC motor and dynamo. As a child, he dreamed of harnessing the energy of Niagara Falls. In his early 30s he conceived an idea of an AC motor, and built a crude prototype. He became employed at Thomas Edison's European division but came to the United States to work directly for him. He hoped to persuade Edison to adopt his vision.
AC vs DC Current
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A bitter disagreement between Tesla and Edison led to Tesla's leaving the company and selling his AC system to Edison's rival, George Westinghouse. An acrimonious turf war pitted Edison against Westinghouse and Tesla, but the superiority of AC won out over DC, which is why buildings are powered by alternating currents. Edison's company later became known as General Electric.
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