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'''' An isothermal process is a change of a ''system'', in which the temperature remains constant: Δ''T'' = 0. This typically occurs when a system is in contact with an outside thermal reservoir (heat bath), and the change occurs slowly enough to allow the system to continually adjust to the temperature of the reservoir through heat exchange. In contrast, an ''adiabatic process'' is where a system exchanges no heat with its surroundings (''Q'' = 0). In other words, in an isothermal process, the value Δ''T'' = 0 and therefore Δ''U'' = 0 (only for an ideal gas) but Q ≠ 0, while in an adiabatic process, Δ''T'' ≠ 0 but Q = 0. ==Details for an ideal gas== For the special case of a gas to which Boyle's law applies, the product ''pV'' is a constant if the gas is kept at isothermal conditions. However, in the cases where the product pV is an exponential term this does not comply. The value of the constant is ''nRT'', where ''n'' is the number of moles of gas present and ''R'' is the ideal gas constant. In other words, the ideal gas law ''pV'' = ''nRT'' applies. This means that : holds. The family of curves generated by this equation is shown in the graph presented at the bottom right-hand of the page. Each curve is called an isotherm. Such graphs are termed indicator diagrams and were first used by James Watt and others to monitor the efficiency of engines. The temperature corresponding to each curve in the figure increases from the lower left to the upper right.. 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「Isothermal process」の詳細全文を読む スポンサード リンク
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