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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Seebeck coefficient ： ウィキペディア英語版 Seebeck coefficient The Seebeck coefficient (also known as thermopower,〔Thermo''power'' is a misnomer as this quantity does not actually express a power quantity: Note that the unit of thermopower (V/K) is different from the unit of power (watts).〕 thermoelectric power, and thermoelectric sensitivity) of a material is a measure of the magnitude of an induced thermoelectric voltage in response to a temperature difference across that material, as induced by the Seebeck effect.〔''Concepts in Thermal Physics'', by Katherine M. Blundell (Weblink through Google books )〕 The SI unit of the Seebeck coefficient is volts per kelvin (V/K),〔 although it is more often given in microvolts per kelvin (μV/K). The use of materials with a high Seebeck coefficient is one of many important factors for the efficient behaviour of thermoelectric generators and thermoelectric coolers. More information about high-performance thermoelectric materials can be found in the Thermoelectric materials article. In thermocouples the Seebeck effect is used to measure temperatures, and for accuracy it is desirable to use materials with a Seebeck coefficient that is stable over time. Physically, the magnitude and sign of the Seebeck coefficient can be approximately understood as being given by the entropy per unit charge carried by electrical currents in the material. It may be positive or negative. In conductors that can be understood in terms of independently moving, nearly-free charge carriers, the Seebeck coefficient is negative for negatively charged carriers (such as electrons), and positive for positively charged carriers (such as electron holes). ==Definition== (詳細はcurrent density is zero everywhere. If the temperature difference Δ''T'' between the two ends of a material is small, then the Seebeck coefficient of a material is defined as: :$$ S = - where Δ''V'' is the thermoelectric voltage seen at the terminals. (See below for more on the signs of Δ''V'' and Δ''T''.) Note that the voltage shift expressed by the Seebeck effect cannot be measured directly, since the measured voltage (by attaching a voltmeter) contains an additional voltage contribution, due to the temperature gradient and Seebeck effect in the measurement leads. The voltmeter voltage is always dependent on ''relative'' Seebeck coefficients among the various materials involved. Most generally and technically, the Seebeck coefficient is defined in terms of the portion of electric current driven by temperature gradients, as in the vector differential equation :$\backslash mathbf\; J\; =\; -\backslash sigma\; \backslash boldsymbol\; \backslash nabla\; V\; -\; \backslash sigma\; S\; \backslash boldsymbol\; \backslash nabla\; T$ where $\backslash scriptstyle\backslash mathbf\; J$ is the current density, $\backslash scriptstyle\backslash sigma$ is the electrical conductivity, $\backslash scriptstyle\backslash boldsymbol\; \backslash nabla\; V$ is the voltage gradient, and $\backslash scriptstyle\backslash boldsymbol\; \backslash nabla\; T$ is the temperature gradient. The zero-current, steady state special case described above has $\backslash scriptstyle\backslash mathbf\; J=0$, which implies that the two current density terms have cancelled out and so $\backslash scriptstyle\backslash boldsymbol\; \backslash nabla\; V\; =\; -S\backslash boldsymbol\; \backslash nabla\; T$. 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「Seebeck coefficient」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.