- #1
yungman
- 5,718
- 241
The electric field at a point P pointed by the position vector [itex] \vec r \;\hbox {, from a moving point charge pointed by a position vector }\;\vec w(t_r)\;[/itex] at the retarded time is given by:
[tex]\vec E_{(\vec r,t)} = \frac q {4\pi\epsilon_0}\frac{\eta}{(\vec{\eta}\cdot \vec u)^3}[(c^2-v^2)\vec u + \vec{\eta}\times(\vec u\times \vec a)][/tex]
[tex]\hbox{Where }\; \vec {\eta}=\vec r -\vec w(t_r) \;,\;\; \vec u = c\hat{\eta}-\vec v\;,\;\; \vec v =\frac{d \vec w(t_r)}{dt} \;\hbox { is the velocity vector of point charge } \;,\; \vec a = \frac{d \vec v}{dt}[/tex]
My question is what is the physical meaning of [tex] \vec u = c\hat{\eta}-\vec v [/tex]
[tex]\vec E_{(\vec r,t)} = \frac q {4\pi\epsilon_0}\frac{\eta}{(\vec{\eta}\cdot \vec u)^3}[(c^2-v^2)\vec u + \vec{\eta}\times(\vec u\times \vec a)][/tex]
[tex]\hbox{Where }\; \vec {\eta}=\vec r -\vec w(t_r) \;,\;\; \vec u = c\hat{\eta}-\vec v\;,\;\; \vec v =\frac{d \vec w(t_r)}{dt} \;\hbox { is the velocity vector of point charge } \;,\; \vec a = \frac{d \vec v}{dt}[/tex]
My question is what is the physical meaning of [tex] \vec u = c\hat{\eta}-\vec v [/tex]