# I A few questions about charged particles

1. Apr 14, 2016

### Samson4

I understand the basic forces moving charges experience in magnetic fields. I dont; however, understand how these these charges would interact with particles uninfluenced by the magnetic field.

1. If a charged particle is moving perpendicular to a uniform magnetic field, it will follow a circular path. Does the particles motion create a magnetic field that interacts with magnetic field that is applying a force to it? For example, will the magnetic field strength inside the circular path be at a higher density than outside the path of the particle?

2. If an electron is moving in a circular path in a magnetic field, experiencing a lorentz force. But, just inside it's circular path, the magnetic field strength falls off to zero. A positive particle with a velocity perpendicular to this path, originating from the center of the circle, is uninfluenced by the magnetic field. How will the electron and positive particle interact in the area before the positive charge enters the magnetic field?

3. How do oppositely charged particles influence each other if they are moving perpendicular to each other? Is it purely attraction or are their complex magnetic interactions that explain their movements. What terms can I search to research this interaction?

Last edited: Apr 14, 2016
2. Apr 14, 2016

### Staff: Mentor

Magnetic fields from different sources do not really interact with each other - the magnetic fields just add up. Yes, a particle moving in a circle will change the magnetic field (a tiny bit).
Or does it get weaker? You can calculate it to check.
Perpendicular to a circle? So along the magnetic field lines outside?
In the same way they would without magnetic field.
It can get complicated.
You can always take the Maxwell equation and calculate the electric and magnetic field everywhere. Retarded potentials can be useful as well.

3. Apr 14, 2016

### Samson4

No, the positive particles are originating in the center of the electron's circular path, moving perpendicular to the electron.

This interaction would be purely electric? I thought it would have a cycloid type motion because of a lorrentz force due to a magnetic field acompaning the electrons circular path.

4. Apr 14, 2016

### Staff: Mentor

In general, if anything is moving relative to whatever you want to consider, magnetic fields have some influence. Their contribution relative to the electric fields scales with v/c with the velocity v and the speed of light c, so for nonrelativistic particles they are often negligible.