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The elementary charge, usually denoted as or sometimes , is the electric charge carried by a single proton, or equivalently, the negation (opposite) of the electric charge carried by a single electron.〔Note that the symbol ''e'' has many other meanings. Somewhat confusingly, in atomic physics, ''e'' sometimes denotes the electron charge, i.e. the ''negative'' of the elementary charge.〕 This elementary charge is a fundamental physical constant. To avoid confusion over its sign, ''e'' is sometimes called the elementary positive charge. This charge has a measured value of approximately In the cgs system, ''e'' is .〔This is derived from the NIST value and uncertainty, using the fact that one coulomb is ''exactly'' statcoulombs. (The conversion is ten times the numerical speed of light in meters/second.)〕 The magnitude of the elementary charge was first measured in Robert A. Millikan's noted oil drop experiment in 1909.〔(Robert Millikan: The Oil-Drop Experiment )〕 == As a unit == In some natural unit systems, such as the system of atomic units, ''e'' functions as the unit of electric charge, that is ''e'' is equal to 1 e in those unit systems. The use of elementary charge as a unit was promoted by George Johnstone Stoney in 1874 for the first system of natural units, called Stoney units.〔 〕 Later, he proposed the name ''electron'' for this unit. At the time, the particle we now call the electron was not yet discovered and the difference between the particle ''electron'' and the unit of charge ''electron'' was still blurred. Later, the name ''electron'' was assigned to the particle and the unit of charge ''e'' lost its name. However, the unit of energy electronvolt reminds us that the elementary charge was once called ''electron''. The maximum capacity of each pixel in a charge-coupled device image sensor, known as the ''well depth'', is typically given in units of electrons,〔(Apogee CCD University – Pixel Binning )〕 commonly around 105 e– per pixel. 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「elementary charge」の詳細全文を読む スポンサード リンク
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