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Definitions of electrical terms
Exploring electricity
The effects of electricity have been known about since antiquity. But it wasn't until the 18th and 19th centuries that enough was learned to put it to practical use.
With knowledge and the inventions that followed, various types of electricity were defined and the electrical vocabulary we use today came into being.
see also ...
Faraday's work
electro-magnetic rotations
electrical transformer
electrical generator
The command of electricity
History of public supply
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Definitions of electrical terms
current
A flow of electrons, i.e., a flow of electricity. Measured in amperes (A).
electric battery
A battery (or voltaic pile) is a device for making electricity by chemical means. In the 1790s, Alessandro Volta  (1745-1827)  discovered that if pieces of different metals were piled on top of each other separated by cardboard soaked in an acid, an electric current was produced. Despite all the developments since, the principle of the battery remains the same.
electricity
These days, electricity is thought of in terms of the flow of electrons (tiny charged particles) passing along a wire. It is the manifestation of a form of energy. From the 18th century to the middle of the 19th century, though, electricity was thought of as an imponderable (weightless) material fluid (or fluids) flowing through a wire, the way water flows through a pipe. Michael Faraday was the first to argue that electricity was a force. However, he opposed the atomic conception of matter and was therefore unable to make the leap to an electron theory.
..... see also The command of electricity
electric motor
A machine that converts electrical energy into mechanical energy. An early form was invented by Michael Faraday in 1821. He found that a wire carrying an electric current rotated round a magnet. Thus he demonstrated that it was possible to obtain motion from the combination of electricity and magnetism. This encouraged the development of the modern electric motor which uses the interaction of magnetic fields, produced electrically, to cause motion.
..... see also electro-magnetic rotations
electro-magnetic rotations
The principle behind the electric motor. In 1821, Michael Faraday discovered that a vertically mounted wire carrying an electric current would rotate continuously round a magnet protruding from a bowl of mercury. This phenomenon, which Faraday called electro-magnetic rotations, showed that it was possible to produce continuous motion from the interaction of electricity and magnetism.
..... see also electro-magnetic rotations
electro-magnetism
Electro-magnetism describes the relationship between electricity and magnetic force. Certain metals can be made magnetic by passing an electric current through a coil wound around a piece of them. A report of the discovery of this effect was published in 1820 by Hans Christian Oersted  (1777-1851).
galvanometer
A device for showing the presence and measuring the quantity of electricity. When an electrical current is passed through the coil of a galvanometer, a magnetic needle near the coil is deflected. This can be calibrated to provide a measure of the quantity of electricity. The galvanometer was invented following Hans Christian Oersted's discovery of electro-magnetism in 1820, and was named after Alessandro Volta's great electrical rival, Luigi Galvani.
generator
The electric generator was invented by Michael Faraday in 1831 in the course of his work exploring electro-magnetic induction. It's a device with a magnet, or something performing the function of a magnet, that moves in the vicinity of a coil of wire to generate an electric current in the wire. Virtually all electric power is produced using this principle, no matter whether the prime source of energy is coal, oil, gas, nuclear, hydro, or wind, etc.
..... see also electrical generator
magnetism
The attractive power of magnets. It's caused by electron spin in materials containing unpaired electrons. Although known about since antiquity through, for example, the lodestone (a natural magnet), explanations tended to be descriptive. Even in the 19th century, magnetism was ascribed as a property of its lines of force. Michael Faraday showed that all matter, including gases, possesses magnetic properties.
Ohm's law
Ohm's law relates electro-motive potential difference (V) to current (I) and resistance (R) using the formula V=IR. Georg Simon Ohm  (1789-1854)  published his law in 1827.
power
The rate of energy transfer in a system. Measured in watts (W).
resistance
A measure of the opposition to the flow of an electric current in a substance. Electrical resistance is measured in ohms (Ω).
tension
Electromotive force, nowadays defined as the potential difference between two points in an electrical circuit. Tension is measured in volts (V).
transformer
The transformer was invented by Michael Faraday in 1831 to enable him to demonstrate the phenomenon of electro-magnetic induction. In a transformer, two coils of wire are wound on opposite sides of a metal core. When an electric current is passed into one coil, a transient electric current is induced in the other. By varying the number of windings round the coils, the voltage can be increased or decreased. Because induction is a transient phenomenon, the transformation can be repeated very quickly. Electrical substations are large transformers, and thus the device is key to efficient transmission of high voltage alternating current (AC).
..... see also electrical transformer
Van de Graaff generator
A machine for generating very high voltage static electricity. It uses a high speed belt rubbing against a hollow metal sphere, which acts as a capacitor. Modern uses include X-ray tubes and the acceleration of electrons for food sterilization. The generator was developed by American physicist Robert J. Van de Graaff  (1901-1966), who began work on it in 1929.

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