# Thread: SR and EM easy question

1. Lots of webpages on the net using electron and current wire to show E = M depending on which frame you're in.

Question can anyone give me a webpage/reference which analyses the equations of motion of the electron?

I've heard it's a parabola in the wire's rest frame, but since the EM forces vary with radial distance from the wire I can't see why it should be.  2. Originally Posted by raymondo Lots of webpages on the net using electron and current wire to show E = M depending on which frame you're in.

Question can anyone give me a webpage/reference which analyses the equations of motion of the electron?

I've heard it's a parabola in the wire's rest frame, but since the EM forces vary with radial distance from the wire I can't see why it should be.

Here is a good page.  3. Can't find equations of motion.  4. Originally Posted by raymondo Can't find equations of motion.
Here  5. I'm referring to a different experiment. An electron is fired // to a current carrying wire. In the rest frame of the wire the force acting on the electron is purely magnetic, tensor transform to co moving frame and the force is purely electric. Lots of webpages deal with this experiment, often using length contraction instead of EM tensor transform. Do you know of a webpage/reference which analyses and solves the EoM of the electron in each frame?  6. Originally Posted by raymondo I'm referring to a different experiment. An electron is fired // to a current carrying wire. In the rest frame of the wire the force acting on the electron is purely magnetic, tensor transform to co moving frame and the force is purely electric. Lots of webpages deal with this experiment, often using length contraction instead of EM tensor transform. Do you know of a webpage/reference which analyses and solves the EoM of the electron in each frame?
See section 13.6  7. Yes, that's the experiment all right but notice that the equations of motion for the electron are not solved at all.
That' my problem: I can't find a webpage that solves the EoM of the electron. In a general solution of the EoM the coordinates are expressed in terms of the proper time for each frame of reference and then by eliminating the proper time in each frame, the trajectory of the electron in each frame can be derived.

Do you know of a webpage where the EoM are solved and the trajectories derived?  8. Originally Posted by raymondo Yes, that's the experiment all right but notice that the equations of motion for the electron are not solved at all.
That' my problem: I can't find a webpage that solves the EoM of the electron. In a general solution of the EoM the coordinates are expressed in terms of the proper time for each frame of reference and then by eliminating the proper time in each frame, the trajectory of the electron in each frame can be derived.

Do you know of a webpage where the EoM are solved and the trajectories derived?
For THIS particular experiment there is no need to solve the equations of motion since the electron must follow the direction of the wire. For FREE electrons (a different subject), the previous link I gave you gives the equations of motion. You can also get them here.  9. Still not got it - can't find EoMs of electron launched outside the wire. The fields are non constant so I don't know how to find the trajectory of the electron.  Posting Permissions
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