# Motion of charged particle in uniform magnetic field

To create a uniform magnetic field I took a current carrying solenoid connected to a battery, then I took a long straight wire connected to another battery, the wire passes from inside the solenoid. We know that motion of a charged particle in uniform magnetic field is helical (in the case when $\mathrm{sin~a}$ is not zero ). So my question is what will be the motion of electrons inside the current carrying wire.. will it be helical? What will be the effect on current carrying wire on its current, potential, etc...

## 1 Answer

The situation described here is not that simple. First of all we see a simple situation. You have a solenoid and generate an appreciable magnetic field inside it.

Now you put a charged particle (electron) into it (not the wire with current), It is also assumed that the mean free path of this charged particle is quite large such that it do not collide with anything (gas molecules) inside the solenoid. Now if this particle is launched at an angle then yes it will go in helical path. If the magnetic field is small enough then the electron will collide with the wall of the solenoid.

Now come to the wire. Inside wire the electrons have very small mean free path. Now these electrons will frequently collide with the neighboring atoms and will not go in helical path but they will follow random path more or less same without magnetic field. However $r=mv/qB$ and hence if B is large enough it might happen that one or another electron will eventually complete one circle without colliding with neighboring atoms but one should not be very hopeful for this.

• Thanks for the helping me. cuz i just had a thought while i was studying this . Jul 20, 2016 at 18:04