- #1
mysearch
Gold Member
- 526
- 0
Hi,
I am trying to get a better idea of how E-field line diagrams are drawn. The following link appears to be a nice example of field lines associated with a single charge moving linearly with constant velocity [v=0.5c]. By default, after pressing go, the animation displays the field lines for a single charge moving along the x-axis at a constant velocity [v=c/2]. If you stop this animation at any point, the vertical field line is always a line that points straight up. http://www.its.caltech.edu/~phys1/java/phys1/MovingCharge/MovingCharge.html
However, I would like to better understand the rules by which this line is drawn.
Basic Rules:
For each location, the electric field vector is tangent to the direction of the electric field line at any given point? The direction of resultant field vector is the vector sum of all the charges present?
Example:
To describe the problem I am trying to resolve – see attached diagram. This diagram is essentially a freeze frame, which would appear to be equivalent to the animation cited above. There is only 1 charge, so the electric field is assumed to propagate with velocity [c] in all directions, while the charge propagates with a relativistic velocity [v=c/2] from left to right. However, the example freeze frame only focuses on just the vertical field line and attempts to determine the field vector direction at 3 offset points, e.g. p1, p2, p3. At this frozen moment in time, the charge has just arrived a t=0, allowing no time for updates of the electric field to have propagated from this position towards p1, p2, p3. As such, it would seem that the field vector at p1, p2, p3 must reflect the field strength propagated from an earlier position of the charge, which is resolved to a granularity of [dt]. What the diagram suggests is that due to the combination of the charge velocity [v] and the field propagation velocity [c], the field vectors at p1, p2, p3 all point in different directions at the time of the frozen frame, i.e. t=0.
Just such, I don’t understand how the field line can be said to point straight up, if the electric field vector has to be tangent to the direction of the electric field lines at any given point. Therefore, I would appreciate any insights that explain this aspect of field lines. Thanks
I am trying to get a better idea of how E-field line diagrams are drawn. The following link appears to be a nice example of field lines associated with a single charge moving linearly with constant velocity [v=0.5c]. By default, after pressing go, the animation displays the field lines for a single charge moving along the x-axis at a constant velocity [v=c/2]. If you stop this animation at any point, the vertical field line is always a line that points straight up. http://www.its.caltech.edu/~phys1/java/phys1/MovingCharge/MovingCharge.html
However, I would like to better understand the rules by which this line is drawn.
Basic Rules:
For each location, the electric field vector is tangent to the direction of the electric field line at any given point? The direction of resultant field vector is the vector sum of all the charges present?
Example:
To describe the problem I am trying to resolve – see attached diagram. This diagram is essentially a freeze frame, which would appear to be equivalent to the animation cited above. There is only 1 charge, so the electric field is assumed to propagate with velocity [c] in all directions, while the charge propagates with a relativistic velocity [v=c/2] from left to right. However, the example freeze frame only focuses on just the vertical field line and attempts to determine the field vector direction at 3 offset points, e.g. p1, p2, p3. At this frozen moment in time, the charge has just arrived a t=0, allowing no time for updates of the electric field to have propagated from this position towards p1, p2, p3. As such, it would seem that the field vector at p1, p2, p3 must reflect the field strength propagated from an earlier position of the charge, which is resolved to a granularity of [dt]. What the diagram suggests is that due to the combination of the charge velocity [v] and the field propagation velocity [c], the field vectors at p1, p2, p3 all point in different directions at the time of the frozen frame, i.e. t=0.
Just such, I don’t understand how the field line can be said to point straight up, if the electric field vector has to be tangent to the direction of the electric field lines at any given point. Therefore, I would appreciate any insights that explain this aspect of field lines. Thanks
Attachments
Last edited: