Is it true that if you put negatively charged particles under magnetic field it will circulate continuously ?

[jerryyu]

It will also be helpful if you can give example. Thanks you.

[The Foot Tapper]

The fine beam tube is the classic demonstration - Helmholz coils are used to deflect cathode rays.

[timo]

I'm somewhat confused. Wasn't the question answered quite exhaustively in a previous thread of yours (http://www.scienceforums.net/topic/50243-is-it-possible-to-change-the-direction-of-ions-with-magnetic-field/)?

In practice, the charged particles will not circulate continuously but stop that motion sooner or later; be it because of radiating off energy or more simply because of collisions with other particles. A sample application is bubble chambers where from the curvature of the path you can deduct some properties of the particles (e.g. identify anti-electrons from the opposite direction of rotation).

[jerryyu]

Quite not though. I remember in that thread all the posts were about how magnetic field couldn't increase the speed of the negatively charged ions and how the field can alter the path of the ions.

 

But what if I used a particle shooter that shoots particle individually, won't that eases the possibility of collisions.

[swansont]

If the particle is moving, the magnetic field will deflect it. As the force is perpendicular to the motion, this will tend to cause circular motion. But an accelerating free charge radiates, which will mean it loses energy as this happens.

[jerryyu]

An accerlerating free charge radiates light, thus loses energy?

 

Is there an explanation for that phenomenon ? ( why it happens)

[swansont]

An accerlerating free charge radiates light, thus loses energy?

 

Is there an explanation for that phenomenon ? ( why it happens)

You have an electric and magnetic field for a moving charge. When there is an acceleration you basically create a "ripple" in the EM field, which is the emitted radiation.

 

http://en.wikipedia.org/wiki/Bremsstrahlung

[jerryyu]

let just say I had a moving magnetic field close to the circulating ions, will that helps the moving ions to gain back the energy they lost?

[swansont]

let just say I had a moving magnetic field close to the circulating ions, will that helps the moving ions to gain back the energy they lost?

 

It can; it will depend on the motion. A moving magnetic field looks like an electric field in the other frame, so it can do work.

[Duda Jarek]

I can't believe - (classical) ion trajectories in EM ... and swansont doesn't move it to speculations, but take a part in it ...

Very interesting this kind of considerations are so called 'geonium atoms' in Penning trap, used for example to measure g-factor: http://heart-c704.uibk.ac.at/LV/AtomMolekul/dehmelt86.pdf

Don't worry - because of Heisenberg principle, we cannot fully know e.g. initial conditions - we have to assume some probability density among scenarios - all trajectories should finally stabilize in the trap, so propagating this probability we should finally assume some probability cloud of electron - which have magnetic moment, so there is precessive motion involved(zitterbewegung), so we should use some order parameter describing expected relative phases in different places of this periodic internal motion of electron (like in superconducting ring) - Schroedinger's picture

[swansont]

What does this have to do with the OP?

[Duda Jarek]

OP?

It's a thread about classical trajectory of charged particle in magnetic field - without magnetic momentum, on exactly perpendicular plane, it would 'circulate continuously', but generally it remains its momentum along magnetic field, so finally it makes kind of helix ...

To make such trajectory bounded, we use e.g. Penning trap - and I thing in such papers jerryyu will find satisfactory answers, untrue?

But generally we cannot know precisely these conditions, so we just have to use some statistical ensemble among possible scenarios - use probabilistic picture like Schroedinger's one, do you disagree?

[swansont]

OP = original post or original poster

 

The question was indeed about classical trajectories in a magnetic field. Penning traps have electric fields in addition, and the mention of Heisenberg and Schrödinger means you are not discussing a classical system.

 

 

 

!

Moderator Note

Discussion on trajectories moved http://www.scienceforums.net/topic/51938-uncertainty-in-classical-trajectories/

Edited September 23, 2010 by swansont
add link

[jerryyu]

You have an electric and magnetic field for a moving charge. When there is an acceleration you basically create a "ripple" in the EM field, which is the emitted radiation.

 

http://en.wikipedia.org/wiki/Bremsstrahlung

 

Wait, i went and search on it( the Bremsstrahlung occurs when the electrons is deflected by an atom- thus emitting radiation.) So does that mean if negatively-charged ions were traveling in a vacuum, then it weren't emit radiation?

[swansont]

Wait, i went and search on it( the Bremsstrahlung occurs when the electrons is deflected by an atom- thus emitting radiation.) So does that mean if negatively-charged ions were traveling in a vacuum, then it weren't emit radiation?

 

At constant velocity it would emit no radiation.

[jerryyu]

At constant velocity it would emit no radiation.

 

since it would emit no radiation then no energy will be lost? or is there another way the energy can be lost for moving negatively-charged ions?

[swansont]

since it would emit no radiation then no energy will be lost? or is there another way the energy can be lost for moving negatively-charged ions?

 

It has to interact with something in order to lose energy.