关键词: 推迟势, Lienard-Wiechert势, 点电荷

Abstract: The retarded potential of a continuous charge distribution and the Lienard-Wiechert potential of a moving point charge are both key and challenging topics in undergraduate electrodynamics courses. This study constructs examples of continuous charge distributions analytically solvable with elementary mathematics, and presents graphical analyses of the charge distribution and total charge perceived by an observer. These examples are intended to aid in understanding the semi-intuitive derivation of the Lienard–Wiechert potential as presented in Griffiths classic textbook. This work helps clarify that the perceived charge is unrelated to relativistic length contraction, provides an intuitive picture of the finite speed of electromagnetic interaction transmission, and deepens the understanding of point charges in classical electrodynamics. 

Key words: Retarded potential, Lienard-Wiechert potential, point charge