给出了两种计算电介质中极化电荷密度的方法.（1）介质内部极化电荷密度等于极化强度矢量的散度的负值，ρP=-▽·P；（2）介质内部极化电荷密度与介质的极化率、介质内自由电荷密度以及极化率梯度与电场强度之间的相互作用有关，ρP=-χeχe+1ρf-χε0e+1▽χe·E.针对电荷分布具有一定对称性的问题，分别利用这两种方法分析了电介质均匀且内部不存在自由电荷、电介质均匀但内部存在自由电荷以及电介质不均匀且内部不存在自由电荷情况下介质内部的极化电荷密度，并通过实例加以详尽的讨论.%Two calculation methods of polarization charge density in dielectric are given in this paper. (1)The polarization charge density is equal to the negative value of the polarization vector divergence ,ρP=-▽·P;(2)The po larization charge density is determined by the polarizability,the free charge density,the polarization gradient and the electric field intensity,ρP=- χeχe+1 ρf-χε0e+1 ▽χe·E . For the situation of the charge distribution with certain symme-try,using the two methods,the polarization charge density is calculated respectively for the three cases:the uniform dielectric without free charge in it,the uniform dielectric with free charge in it,and nonuniform dielectric without free charge in it. It is discussed in detail by examples.
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