The transformation relations of the four-dimensional potential vector were first given in the paper and then the relations were discussed by using the infinite long carries straight wire. It can be found that the method of potential transformation rel~ttions was easy, and the unity and relativity of the electromagnetic field was also reflected.%首先得出四维势矢量的变换关系，以无限长载流直导线为例，运用势的基本求法和势的变换关系分别对其进行讨论研究，发现利用势的变换关系求解要较为简便，而且其更能反映电磁场的统一性和相对性．
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