Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Equations for Arc Plasma near Magnetic Fields

  1. Feb 29, 2004 #1
    Hi, I'm currently doing an research experiment into the behaviour of plasma around magnetic fields. I will be using an arc welding machine for the plasma and an electromagnet. (So I can adjust the field's intensity as an independant variable.) The arc should bend in the presence of a magnetic field, and the how much it bends is dependant on the strength of the field. What I need to do is to be able to calculate/predict how much the plasma will bend if I know;
    *The momentum of the plasma,
    *The magnitude of the magnetic field,
    *The kinetic energy of the plasma,
    *The heat energy caused when the plasma strikes a surface.

    Firstly, is there any way I can calculate the momentum and the kinetic energy if I know the heat energy given off when the plasma strikes a surface? If not, is there any other way I could find the plasma's p and KE?

    And, furthermore, (and more importantly,) is there any way, to calculate how much the arc bends once I know the momentum, kinetic energy and magnetic field magnitude? If not, what should I be measuring to calculate how much the arc bends?

    I can deal with rather complex maths, but, as I'm only a highschool freshman and haven't learned too much calculus, the simpler the better.

    Regards;
    -Alice.

    PS: Sorry if this doesn't make a lick of sense, I may have gotten a bit mixed-up somewhere along the line. I'm relatively new to physics, you see.

    EDITED: To spare you all some tedious background info on yours truly.
     
    Last edited: Feb 29, 2004
  2. jcsd
  3. Mar 1, 2004 #2

    Haelfix

    User Avatar
    Science Advisor

    Dear Alice, I assume this is for a science project or something.

    While your idea is good, its going to be hellish to pull off experimentally.

    First problem
    1) You need a huge magnetic field to observe bending of a relatively midly charged plasma. I say midly charged, b/c it won't stay ionized very long in air.
    2) The magnetic field needs to be nice and uniform, or else all hell breaks loose for predictivity. In other words, you need a big solenoid not found in your local Kmart!
    3) The plasma itself is molecularly complicated in your example, it will also interact with air particles, since it doesn't live in a relative vacuum. Eg you really want to do this experiment with a very pure plasma of a simple particle species, in a vacuum =D
    The problem is, getting a decent vacuum is not something you can find in your local Kmart either!
    4) You also want a very controlled emission. Say a very nice and uniform jet of plasma, so that the mean velocity doesn't have error bars that are off the chart.

    The point is, its too hard a project for a high school student. What you can do however, is to derive some theoretical predictions for various plasma jets. This is usually acceptable work for a science project, in which case everything can be treated ideally. Ask again for more details
     
  4. Mar 1, 2004 #3

    chroot

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The only equation you need is the Lorentz force law:

    [tex]F = q(\vec E + \vec v \times \vec B)[/tex]

    When the electric field, [itex]\vec E[/itex] is zero, this reduces to simply:

    [tex]F = q( \vec v \times \vec B)[/tex]

    - Warren
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Equations for Arc Plasma near Magnetic Fields
Loading...