Jean Baptiste Joseph Fourier
Fourier was a French mathematician and physicist best known for initiating the investigation of Fourier series and their application to problems of heat flow. The Fourier transform is also named in his honour. Fourier is also generally credited with the discovery of the greenhouse effect.
Fourier was born at Auxerre, France, the son of a tailor. He was orphaned at age nine. Fourier was educated by the Benvenistes of the Convent of St. Mark. The commissions in the scientific corps of the army were reserved for those of good birth, and being thus ineligible, he accepted a military lectureship on mathematics. He took a prominent part in his own district in promoting the French Revolution, and was rewarded by an appointment in 1795 in the École Normale Supérieure.
Fourier went with Napoleon Bonaparte on his Egyptian expedition in 1798, and was made governor of Lower Egypt and secretary of the Institut d'Égypte. Cut off from France by the English fleet, he organized the workshops on which the French army had to rely for their munitions of war. He also contributed several mathematical papers to the Egyptian Institute (also called the Cairo Institute) which Napoleon founded at Cairo, with a view of weakening English influence in the East. After the British victories and the capitulation of the French under General Menou in 1801, Fourier returned to France, and was made prefect of Isère, and it was while there that he made his experiments on the propagation of heat.
In 1822 he published his theory, in which he bases his reasoning on Newton's law of cooling, namely, that the flow of heat between two adjacent molecules is proportional to the extremely small difference of their temperatures. In this work he claims that any function of a variable, whether continuous or discontinuous, can be expanded in a series of sines and cosines of multiples of the fundamental frequency of the waveform.
Fourier creates a lot of other theories but the theory represents the waveforms in sinusoidal series was the most famous and helpful theory. In the field of electrical engineering we are using this theory to represent the harmonic contents in voltage and current of different power system components.
For more reading visit the following link:
http://en.wikipedia.org/wiki/Fourier_series (in inglish)
Michael Faraday, (22 September 1791 – 25 August 1867) was an English chemist and physicist (or natural philosopher, in the terminology of the time) who contributed to the fields of electromagnetism and electrochemistry.
Faraday studied the magnetic field around a conductor carrying a DC electric current, and established the basis for the electromagnetic field concept in physics. He discovered electromagnetic induction, diamagnetism, and laws of electrolysis. He established that magnetism could affect rays of light and that there was an underlying relationship between the two phenomena. His inventions of electromagnetic rotary devices formed the foundation of electric motor technology, and it was largely due to his efforts that electricity became viable for use in technology.
Faraday was born in Newington Butts, now part of the London Borough of Southwark; but then a suburban part of Surrey, one mile south of London Bridge. His family was not well off. His father, James, was a member of the Sandemanian sect of Christianity. James Faraday had come to London around 1790 from Outhgill in Westmorland, where he had been the village blacksmith. The young Michael Faraday, one of four children, having only the most basic of school educations, had to largely educate himself. At fourteen he became apprenticed to a local bookbinder and bookseller George Riebau and, during his seven-year apprenticeship, he read many books, including Isaac Watts' The Improvement of the Mind, and he enthusiastically implemented the principles and suggestions that it contained. He developed an interest in science, especially in electricity. In particular, he was inspired by the book Conversations in Chemistry by Jane Marcet.
Faraday's greatest work was probably with electricity and magnetism. The first experiment which he recorded was the construction of a voltaic pile with seven halfpence pieces, stacked together with seven disks of sheet zinc, and six pieces of paper moistened with salt water. With this pile he decomposed sulphate of magnesia.
Michael FaradayFaraday's breakthrough came when he wrapped two insulated coils of wire around an iron ring, and found that upon passing a current through one coil, a momentary current was induced in the other coil. This phenomenon is known as mutual induction. The iron ring-coil apparatus is still on display at the Royal Institution. In subsequent experiments he found that if he moved a magnet through a loop of wire, an electric current flowed in the wire. The current also flowed if the loop was moved over a stationary magnet. His demonstrations established that a changing magnetic field produces an electric field. This relation was modelled mathematically by James Clerk Maxwell as Faraday's law, which subsequently became one of the four Maxwell equations. These in turn have evolved into the generalisation known today as field theory.
Faraday later used the principle to construct the electric dynamo, the ancestor of modern power generators.
In 1839 he completed a series of experiments aimed at investigating the fundamental nature of electricity. Faraday used "static", batteries, and "animal electricity" to produce the phenomena of electrostatic attraction, electrolysis, magnetism, etc. He concluded that, contrary to scientific opinion of the time, the divisions between the various "kinds" of electricity were illusory. Faraday instead proposed that only a single "electricity" exists, and the changing values of quantity and intensity (voltage and charge) would produce different groups of phenomena.
Near the end of his career Faraday proposed that electromagnetic forces extended into the empty space around the conductor. This idea was rejected by his fellow scientists, and Faraday did not live to see this idea eventually accepted. Faraday's concept of lines of flux emanating from charged bodies and magnets provided a way to visualise electric and magnetic fields. That mental model was crucial to the successful development of electromechanical devices which dominated engineering and industry for the remainder of the 19th century.
For more reading visit the following link:
http://en.wikipedia.org/wiki/Michael_Faraday (In English)