The Dawn of Amateur Radio in the U.K. and Greece | Page 4

the world's first system of signaling by the use of electricity.
In 1837 Charles Wheatstone and William Cooke took out a patent for the world's first Five-needle Telegraph, which was installed between Paddington railway station in west London and West Drayton station a few miles away. The five copper wires required for this system were embedded in blocks of wood.
Electrolysis, the chemical decomposition of a substance into its constituent elements by the action of an electric current, was discovered by the English chemists Carlisle and William Nicholson (1753-1815). If an electric current is passed through water it is broken down into the two elements of which it is composed -- hydrogen and oxygen. The process is used extensively in modern industry for electroplating. Michael Faraday (1791-1867) who was employed as a chemist at the Royal Institution, was responsible for introducing many of the technical terms connected with electrolysis, like electrolyte for the liquid through which the electric current is passed, and anode and cathode for the positive and negative electrodes respectively. He also established the laws of the process itself. But most people remember his name in connection with his practical demonstration of electromagnetic induction.
In France Andre-Marie Ampere (1775-1836) carried out a complete mathematical study of the laws which govern the interaction between wires carrying electric currents.
In Germany in 1826 a Bavarian schoolmaster Georg Ohm (1789-1854) had defined the relationship between electric pressure (voltage), current (flow rate) and resistance in a circuit (Ohm's law) but 16 years had to elapse before he received recognition for his work.
Scientists were now convinced that since the flow of an electric current in a wire or a coil of wire caused it to acquire magnetic properties, the opposite might also prove to be true: a magnet could possibly be used to generate a flow of electricity.
Michael Faraday had worked on this problem for ten years when finally, in 1830, he gave his famous lecture in which he demonstrated, for the first time in history, the principle of electromagnetic induction. He had constructed powerful electromagnets consisting of coils of wire. When he caused the magnetic lines of force surrounding one coil to rise and fall by interrupting or varying the flow of current, a similar current was induced in a neighbouring coil closely coupled to the first.
The colossal importance of Faraday's discovery was that it paved the way for the generation of electricity by mechanical means. However, as can be seen from the drawing, the basic generator produces an alternating flow of current.(A.C.)
Rotating a coil of wire steadily through a complete revolution in the steady magnetic field between the north and south poles of a magnet results in an electromotive force (E.M.F.) at its terminals which rises in value, falls back to zero, reverses in a negative direction, reaches a peak and again returns to zero. This completes one cycle or sine wave. (1Hz in S.I.units).
In recent years other methods have been developed for generating electrical power in relatively small quantities for special applications. Semiconductors, which combine heat insulation with good electrical conduction, are used for thermoelectric generators to power isolated weather stations, artificial satellites, undersea cables and marker buoys. Specially developed diode valves are used as thermionic generators with an efficiency, at present, of only 20% but the heat taken away from the anode is used to raise steam for conventional power generation.
Sir Humphry Davy (1778-1829) one of Britain's leading chemists of the 18th century, is best remembered for his safety lamp for miners which cut down the risk of methane gas explosions in mines. It was Davy who first demonstrated that electricity could be used to produce light. He connected two carbon rods to a heavy duty storage battery. When he touched the tips of the rods together a very bright white light was produced. As he drew the rods apart, the arc light persisted until the tips had burnt away to the critical gap which extinguished the light. As a researcher and lecturer at the Royal Institution Davy worked closely with Michael Faraday who first joined the institution as his manservant and later became his secretary. Davy's crowning honour in the scientific world came in 1820, when he was elected President of the Royal Society.
In the U.S.A. the prolific inventor Thomas Alva Edison (1847-1831) who had invented the incandescent carbon filament bulb, built a number of electricity generators in the vicinity of the Niagara Falls. These used the power of the falling water to drive hydraulic turbines which were coupled to the dynamos. These generators were fitted with a spinning switch or commutator (one of the neatest gadgets Edison ever invented) to make the current flow in unidirectional pulses (D.C.) In 1876 all electrical equipment was powered by direct current.
Today mains electricity plays a vital part in our everyday lives and its applications