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 inducedin 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 thepower 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 are widespread and staggering in their immensity.But we must not forget that popular demand for this convenient form of power arose only about 100 years ago, mainly for illumination.
Recent experiments in superconductivity, using ceramic instead metal conductors have given us an exciting glimpse into what might be achieved for improving efficiency in the distribution of electric power.
Historians of the future may well characterise the 20th century as `the century of electricity & electronics'.But Edison's D.C.generators could not in themselves, have achieved the spectacular progress that has been made.All over the world we depend totally on a system of transmitting mains electricity over long distances which was originally created by an amazing inventor whose scientific discoveries changed, and are still changing, the whole world.His name was scarcely known to the general public, especially in Europe, where he was born.
Who was this unknown pioneer? Some people reckon that it was this astonishing visionary who invented wireless, remote control, robotics and a form of X-ray photography using high frequency radio waves.A patent which he took out in the U.S.A.in 1890 ultimately led to the design of the humble ignition coil which energises billions and billions of spark plugs in all the motor cars of the world.His American patents fill a book two inches thick.His name was Nicola Tesla (1856-1943).
Nicola Tesla was born in a small village in Croatia which at that time formed part of the great Austro-Hungarian Empire.Today it is a northern province of Yugoslavia, a state created after the 1914-1918 war.Tesla studied at the Graz Technical University and later in Budapest.Early in his studies he had the idea that a way had to be found to run electric motors directly from A.C.generators.His professor in Graz had assured him categorically that this was not possible.But young Tesla was notconvinced.When he went to Budapest he got a job in the Central Telegraph Office, and one evening in 1882, as he was sitting on a bench in the City Park he had an inspiration which ultimately led to the solution of the problem.
