坡印亭矢量（Poynting vector）是指电磁场中的能流密度矢量。空间某处的电场强度为E，磁场强度为H，该处电磁场的能流密度为S=E×H，方向由E和H按右手螺旋定则确定，沿电磁波的传播方向。大小为S=EHsinθ，θ为E和H的夹角，表示单位时间通过垂直单位面积的能量，单位为瓦/（米2）。
本文用功能关系和坡印亭矢量分析和讨论了电容器并联过程中能量的变化原因。
With the principle of work and power, as well as Poynting vector, the reasons for the energy variation in the process of connecting capacitances in parallel are analyzed and discussed.
通过对坡印亭矢量的散度的分析，阐明了电机气隙中径向能流和切向能流的变化和传递。
The variation and transmit of the radial and tangential energy flow in the air gap of electrical machines are illustrated by analyzing the divergence of Poynting vector.
利用时间平均的坡印亭矢量，给出了在晶体和介质界面发生负折射的条件，与晶体物理学中的分析结果一致。
The time-averaged Poynting vector gives the conditions for negative refraction that occurs at the interface, which are consistent with the analysis in crystal physics.
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