Trajectory of charged particle moving in a magnetic field

In summary, the conversation discusses the movement of a proton in a magnetic field and its trajectory. It is explained that the proton's motion is influenced by the magnetic field lines, causing it to move in a helical motion. The direction of the proton's initial velocity is along the green lines, and the blue lines represent the current velocity. The pink lines in the diagram are the magnetic field lines, and the particle's initial velocity is diagonal to them. The conversation also mentions that the particle's inertia is responsible for its movement in the direction of the magnetic field lines.
  • #1
BogMonkey
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0
In this video here are those pink green the magnetic field lines?

If so where does the proton come from? If I'm not mistaken a charged particle in motion will only be influenced by the magnetic field if its not moving parallel to the magnetic field lines but in this video the proton appears to be moving in the direction of the magnetic field lines its only the centripetal motion that's perpendicular to the green lines. Does that mean the proton flies into the magnetic field then gets stuck in that circular trajectory? If so what's causing it to move in the direction of the magnetic field lines?

For example in this diagram
http://img59.imageshack.us/img59/4016/mfield114.gif [Broken]
Would that black arrow be the direction that the charged particle comes in or are the pink arrows the direction of the particles velocity before it entered the magnetic field?
 
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  • #2
BogMonkey said:
If I'm not mistaken a charged particle in motion will only be influenced by the magnetic field if its not moving parallel to the magnetic field lines but in this video the proton appears to be moving in the direction of the magnetic field lines its only the centripetal motion that's perpendicular to the green lines.
You are partly right. There is no influence parallel to the magnetic field. No influence means no force. By Newtons first law this means the particle will keep a constant velocity in this direction. So basically the particle is moving in that the direction, because nothing stops it.

BogMonkey said:
Does that mean the proton flies into the magnetic field then gets stuck in that circular trajectory?
Yes, in a constant magnetic field, a proton will exhibit helical motion.

BogMonkey said:
If so what's causing it to move in the direction of the magnetic field lines?
Just inertia.

BogMonkey said:
Would that black arrow be the direction that the charged particle comes in or are the green arrows the direction of the particles velocity before it entered the magnetic field?
The green arrows are the path of the particle in the magnetic field. I suppose the particle came from outside the sketch where there is no magnetic field. Not sure what the black arrow is for.
 
  • #3
Damn I meant to say pink lines in the diagram not green lines. What I was really asking is if the pink lines are the magnetic field lines. I see that the green circular lines are the trajectory of the particle but I'm wondering if the particles initial velocity upon entering the magnetic field is parallel or perpendicular to those pink lines. Or would it be that blue line denoted v?

Gerenuk said:
Just inertia.
Is this inertia always in the direction of the magnetic field lines?
 
  • #4
The pink lines are the magnetic field. The particles initial velocity is along the green lines. So it's basically somehow diagonal. If it were parallel to the magnetic field, then it would go on a straight line. It it were perpendicular to the magnetic field then, it would go in circles at a fixed position. The blue lines are the current velocity of the particles.

Basically two things happen:
The vector component of the velocity along the magnetic field stay unaffected. The vector component perpendicular to the magnetic field turns around so that the particle circles around magnetic field lines.
 
  • #5
Ah right that explains it. Thanks a lot.
 

1. What is the equation for calculating the trajectory of a charged particle in a magnetic field?

The equation is F = qv x B, where F is the force on the particle, q is the charge of the particle, v is its velocity, and B is the magnetic field strength.

2. How does the direction of the magnetic field affect the trajectory of a charged particle?

The direction of the magnetic field determines the direction of the force on the particle. The particle will experience a force perpendicular to both its velocity and the magnetic field, resulting in a curved path.

3. How does the strength of the magnetic field affect the trajectory of a charged particle?

The stronger the magnetic field, the greater the force on the particle will be, resulting in a tighter curved path. This means that the particle will move in a smaller radius and at a higher speed.

4. What happens to the trajectory of a charged particle if the magnetic field is turned off?

If the magnetic field is turned off, the particle will continue to move in a straight line with the same velocity as before. This is because there is no longer a force acting on the particle to change its direction.

5. How does the charge of the particle affect its trajectory in a magnetic field?

The force on a charged particle in a magnetic field is directly proportional to the charge of the particle. This means that a particle with a larger charge will experience a greater force and therefore have a different trajectory compared to a particle with a smaller charge.

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