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Contact electrification is a scientific theory from the Enlightenment that attempted to account for all the sources of electric charge known at the time.〔Willem Hackmann, "(The Enigma of Volta's "Contact Tension" and the Development of the "Dry Pile" )", appearing in ''(Nuova Voltiana: Studies on Volta and His Times ) Volume 3'' (Fabio Bevilacqua; Lucio Frenonese (Editors)), (2000) pp. 103-119〕 It has been superseded by more modern notions. In the late 18th century, scientists developed sensitive instruments for detecting 'electrification', otherwise known as electrostatic charge imbalance. The phenomenon of electrification by contact, or ''contact tension'', was quickly discovered. When two objects were touched together, sometimes the objects became spontaneously charged. One object developed a net negative charge, while the other developed an equal and opposite positive charge. Then it was discovered that 'piles' of dissimilar metal disks separated by acid-soaked cloth, Voltaic piles, could also produce charge differences. Although it was later found that these effects were caused by different physical processes - triboelectricity, the Volta effect, differing work functions of metals, and others - at the time they were all thought to be caused by a common 'contact electrification' process. The contact electrification phenomenon allowed the construction of so-called 'frictional' electrostatic generators such as Ramsden's or Winter's machines, but it also led directly to the development of useful devices such as batteries, fuel cells, electroplating, thermocouples. Contact between materials is responsible for such modern electrical technology as semiconductor junction devices including radio detector diodes, photocells, LEDs, and thermoelectric cells. == History == The theory held that static electricity was generated by means of contact between dissimilar materials, and was in close agreement with the principles of static electricity as then understood. It was eventually replaced by the current theory of electrochemistry, namely, that electricity is generated by the action of chemistry and the exchange of electrons between atoms making up the battery. An important fact leading to the rejection of the theory of contact tension was the observation that corrosion, that is, the chemical degradation of the battery, seemed unavoidable with its use, and that the more electricity was drawn from the battery, the faster the corrosion proceeded. The Volta effect (described below) corresponds to a weak electric potential difference developed by the contact of different metals. Nowadays, this is often known as a contact potential difference. This effect was first discovered by Alessandro Volta, and can be measured using a capacitance electroscope comprising different metals. However, this effect does not, by itself, account for the action of electric batteries. A number of high voltage dry piles were invented between the early 19th century and the 1830s in an attempt to determine the answer to this question, and specifically to support Volta’s hypothesis of contact tension. The Oxford Electric Bell is one example. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Contact electrification」の詳細全文を読む スポンサード リンク
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