电场作用能够较明显地改变电介质系统的物理性质，相关的研究和应用越来越受到广泛的关注。本文以平行板电容器置于一个单相流体电介质系统为模型，详细地探讨了均匀静电场对流体电介质系统的压强和摩尔分数的作用效果。基于相平衡的基本原理，利用电场作用下化学势的表达式，导出了气体和液体电介质系统的压强和摩尔分数随电场强度的变化规律。结果表明：压强和摩尔分数的变化与电场强度的平方成正比，还与温度及电介质的摩尔质量、密度和介电常数有关。静电场作用可以使系统的压强上升，也可以改变混合物的摩尔分数，但组分的摩尔分数是增加或减小决定于组分的摩尔质量和密度的相对大小。静电场作用下，液体的变化大于气体的变化。本文的研究成果为测量介电常数、气体的富集和混合液体的组分调控提供了一种新的思路。

Electrostatic field can modify transfer the physical properties of dielectric system, and the related researches and applications attracted more and more attention. This paper discussed in detail the actions of uniform electrostatic field on the pressure and mole fractions of a fluid dielectric system with a model of a single-phase fluid dielectric system with a parallel plate capacitor inside. Based on the principle of phase equilibrium, the variations of pressure and mole fractions of gas and liquid dielectric system with electric field intensity were derived by using the expression of chemical potential with the influence of electric field. The results show that the changes in pressure and mole fraction are not only proportional to the square of electric field strength, but also related to the temperature and the molar mass, density, and permittivity of the dielectric. The actions of electrostatic field can increase the pressure of the system and change the mole fraction of the mixture. However, whether the mole fraction of the component increases or decreases is determined by the relative magnitude of the molar mass and density of the components. Under the actions of electrostatic field, variation of liquid system is more significant than that of gas system. The findings of this research provide a new idea for measuring the dielectric constant, gas enrichment and composition controlling of mixture.