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Electromagnetic field on molecule

  1. May 28, 2015 #1

    it is known that static electrical field can change the direction of movement of water dripping, etc

    I suppose this can also happen with other molecules that are dipoles or somehow influenced by electrical or magnetic field

    my question is what are the equation(s) that describe this influence

    specifically how the strength of electrical/magnetic field can accelerate at which acceleration an amount of water eg a molecule of water, etc

    I need to know what acceleration I can achieve by exposing a molecule of water to an electrical/magnetic field

  2. jcsd
  3. May 28, 2015 #2
    If the electric field is uniform, there is no net force on the dipole. The opposite forces on the positive and negative charge of the dipole cancel out, and the molecule as a whole does not accelerate. The molecule just rotates because of the electric field. If the field is not uniform, then the forces on the positive and negative charges are not equal, and then the molecule has a net force on it, and it accelerates. The force, and therefore the acceleration, depends on how non-uniform the electric field is. The force is expressed in terms of the dipole moment and the gradient of the electric field.
    In the standard experiment of the change in direction of dripping water, the electric field is non-uniform
  4. May 28, 2015 #3
    how much electricity do I need to create a mass spectrometer, that accelerates ions?
    does it accelerate ions in vacuum or air?
    how fast does it accelerate ions?
  5. May 28, 2015 #4
    What do you think? What will be the problem if you try it in air?
  6. May 29, 2015 #5
    I think there will be collisions, but maybe the strength of the field will be adequate to maintain a fairly straight acceleration
  7. May 29, 2015 #6
    how much electricity do I need to create a magnetic field of 0.01–0.015 T
  8. May 29, 2015 #7
    Every collision will change the direction of the ion's velocity. You cannot have a straight trajectory in a gas at normal pressure.
    Is this for a school project? I hope you don't really think of building an accelerator.

    In what units would you want the amount of "electricity" for your second question?
  9. May 29, 2015 #8
  10. May 29, 2015 #9
    Your questions leave the impression that you are not yet understanding the basic principles for such a task.
    The people at MIT were a little more advanced when they started the actual construction.
    I am sure they knew how to find the "amount of electricity" they will need.

    Not that is anything wrong in asking questions, don't get me wrong. :)
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