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Michael Faraday (September 22, 1791 – August 25, 1867) was a British scientist (a physicist and chemist) who contributed significantly to the fields of electromagnetism and electrochemistry.
Michael Faraday was one of the great scientists in history. Some historians of science refer to him as the greatest experimentalist in the history of science. It was largely due to his efforts that electricity became a viable technology. The SI unit of capacitance, the Farad (symbol F) is named after him.
Contributions:
- His greatest work was with electricity. In 1821, soon after the Danish chemist, Hans Christian Ørsted, discovered the phenomenon of magnetism, Humphry Davy and William Hyde Wollaston tried but failed to design an electric motor. Faraday, having discussed the problem with the two men, went on to build two devices to produce what he called electromagnetic rotation: a continuous circular motion from the circular magnetic force around a wire. A wire extending into a pool of mercury with a magnet placed inside would rotate around the magnet if charged with electricity by a chemical battery. This device is known as a homopolar motor. These experiments and inventions form the foundation of modern electromagnetic technology. Unwisely, Faraday published his results without acknowledging his debt to Wollaston and Davy, and the resulting controversy caused Faraday to withdraw from electromagnetic research for several years.
- Ten years later, in 1831, he began his great series of experiments in which he discovered electromagnetic induction. 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. This was the first transformer (inductor), although Faraday used it only to demonstrate the principle of electromagnetic induction and did not foresee the use to which it would eventually be put.
His demonstrations established that a changing magnetic field produces an electric field. This relation was mathematically modelled by Faraday's law, which subsequently became one of the four Maxwell equations. These in turn evolved into the generalization known as field theory.
Faraday then used this principle to construct the first dynamo (in the form of a copper disk rotated between the poles of a permanent magnet), the precursor of modern dynamos and generators.
- In 1832, Michael Faraday reported that the quantity of elements separated by passing an electrical current through a molten or dissolved salt was proportional to the quantity of current passed through the circuit. This became the basis of the first law of electrolysis. He also popularized terminology such as anode, cathode, electrode, and ion.
- In 1845 he discovered what is now called the Faraday effect. The plane of polarization of linearly polarized light propagated through a material medium can be rotated by the application of an external magnetic field aligned in the propagation direction. He wrote in his notebook, "I have at last succeeded in illuminating a magnetic curve or line of force and in magnetising a ray of light". This established that magnetic force and light were related.
- In 1845 he also discovered the phenomenon that he named diamagnetism - a very weak form of magnetism that is only exhibited in the presence of an external magnetic field. This phenomenon can can be used for levitation.
- In his work on static electricity, Faraday demonstrated that the charge only resided on the exterior of a charged conductor, and exterior charge had no influence on anything enclosed within a conductor. This is because the exterior charges redistribute such that the interior fields due to them cancel. This shielding effect is used in what is now known as a Faraday cage.
- Faraday also dabbled in chemistry, discovering chemical substances such as benzene, inventing the system of oxidation numbers, and liquefying gases.
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This article is licensed under the GNU Free Documentation License. It uses material from Wikipedia Encyclopedia article "Michael Faraday"
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