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Charged particle interaction

  1. Sep 23, 2013 #1
    Ok so I have few question and would be happy if someone could answer them or reassure me of the way I think is right, thank you.

    First of all do electrons that have higher energy levels can attract two ions closer than electron with lower energy? Or is it a fundamental property that has to do with a charged particles mass and the corresponding electric field or does the field change if say an electron is coming from a high voltage supply rather than some lower voltage one?

    Secondly if a proton for example travels in a certain straight trajectory it has it's electrical (coulomb) field around it , now if that same proton would travel the same trajectory just now negatively charged plates on both sides of the proton , what would happen , yes I do understand that as negative charge attracts positive the proton would most likely run into the plates but for the sake of an argument let's suppose the proton has high enough kinetic energy to keep the trajectory straight between the plates for a while ,so here is the question would it's surrounding electric field get distorted due to the charged particle field interaction or in other words would the field of the proton become more ellipsoid than round? with the wider sides of the ellipse at the sides of the negatively charged plates due to that's where the attraction forces come from ?
  2. jcsd
  3. Sep 23, 2013 #2


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    Not sure I understand the question. But the strength of the electric field created by an electron depends only on its elementary charge, which does not vary.

    (Note: the speed of the proton doesn't play any role. Just assume that it is travelling exactly midway between the plates.)
    The field of the proton doesn't change. The total electric field will of course depend on both the field of the proton and that of the plates.
  4. Sep 24, 2013 #3
    ok to not mess up many threads ill continue in this one.

    ok let me explain myself a little more , you say that the electric charge of the electron doesn't vary at different voltages for example.There was a thread on this forums a while ago in which the topic was kinda similar and the answer to why one cannot use an electric field to fuse two charged particles into one was that as you increase the field strength (voltage) the strength of the particles surrounding coulomb field also increases.
    Now if this is the case then how come the field not vary ? I guess there is some misunderstanding here in what I mentioned.

    Ok another question. Imagine we have two sets of plates and some structure around them to keep the charged particles confined.
    Now lets add some positive potential to both plates the particles will experience a force say x
    Now add positive potential to one plate and the other plate make negative simple as that + and -, assuming the plates are isolated for the particles to not run into them directly could we say that with the positive and negative plates the particle experiences a force which is x2 rather than just x as with both plates being positive?
  5. Sep 24, 2013 #4


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    Crazymechanic, your writing is incomprehensible. Please try to use correct punctuation to separate sentences and phrases.
  6. Sep 25, 2013 #5
    Well the problem is that my thought runs faster than what I can write so when focusing too much on the one I am missing the other.
    Excuse me, I will try to make myself more clear one more time.

    There was a thread here a while ago, the question in the thread was kinda similar to mine.
    The thought was that ,quote: " You cannot fuse two proton together for example just by using the electric field because as you increase the potential on the plates around those particles , the particle self fields also increase and so they now push against each other with more force? "

    Dr Claude above said that the particle fields don't vary no matter how high or low the applied potential to them so is this true? Like for example an electron coming out of a crt lamp is more energetic than the one coming out of the end terminal of a 9 volt battery.

    And the other question would be like this. Two parallel plates , between them something that keeps the inner side of the plates sealed of the outside.
    Now put some protons between them , in he first case set both plates at some positive potential , the protons are being repelled from both plates they experience some force " x"
    Now do the same setup but instead of setting both plates to a positive potential set the one at positive and the other at negative. The proton now is being repelled from the positive and attracted to the negative.
    What is the force felt by the proton in this case , could we say it's " x2" ?
  7. Sep 25, 2013 #6


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    Could you please point me to that thread? I might be missing something...
  8. Sep 25, 2013 #7


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    I'm not sure that's true. I'm pretty sure you can't do it because in order for electric fields to perform work, you need a DIFFERENCE in potential. Putting two positive electrodes near two particles does nothing but force them out from in between the electrodes, because that's where the difference in potential is. After all, what's the difference in electric potential between 2 electrodes at +100 volts each? Zero.

    Gonna go out on a limb here and say: In case 1, no force is felt towards either electrode, only away from them. (Up/down if you want to call it that) In case 2, I think it would feel twice the force it would feel from just a single electrode being positive or negative.

    I might be wrong on the previous example, but I know that if you try to surround the two particles with something like a positively charged sphere they will feel no force in any direction. So I assume that two parallel electrodes will have no force towards either one, only away from them both, making the particles escape through the "gaps" if you will.
  9. Sep 25, 2013 #8
    @ Dr Claude I will look if I can still find that thread it was years ago when it was made.

    Well technically yes drakkith , two equal voltages can't do work but then again how do you look on it , imagine that you have a box as a containment structure and the plates at each side of the box , the particles have no place to escape but once you turn the plates on the particles (protons) feel repulsion from both sides so they do move in some direction until they find equilibrium point between the two similar forces from both sides and stay there but keeping them in that place is job also or isn't it?

    Surely to have a more profound force and direction one would have to use both positive and negative potentials and manage them in a way so that the protons would feel the force and thus be confined.I'm not saying this can be easily done or something just speaking theoretically now.
    Yeah drakkith the sphere doesn't put force on the particles inside of it when under potential , that's kinda sad.:D

    But still I'm curious if someone with the right knowledge could tell me is it possible to push two protons together using electric field or not ? Even in theory ?
  10. Sep 25, 2013 #9


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    The box is the same scenario as the sphere. And I'm near certain that you can't use purely electric fields to force the fusion of the particles. Well, I take that back. A fusor does just this, except its using an attractive force to keep them passing back and forth through the center until they collide with the grid or another particle. But that's entirely different than forcing them together using repulsive fields.
  11. Sep 25, 2013 #10
    sorry forgot to mention that the box was though of just some non conducting one just to keep our particles " locked" for the sake of an argument, and the plates (conducting material) at the sides so the field should go through to interact with the charged particles.

    Well yes the fusor indeed does this but I guess the problem is in the grid getting the strikes of the particles and the poor confinement achieved so far , by confinement I mean mostly plasma pressures.

    Oh by the way , it's not that I don't enjoy your answer drakkith but somehow you are one of the few who lately responds to any of my threads... that makes me wonder why , even though people here on PF don't know each other personally most of the cases I guess they still form some sympathies towards some and they lack them towards others. Or maybe there is a different reason.
  12. Sep 25, 2013 #11
    Not sure if the plates constitute a "box" in this sense... does this help?

    From 1950s QM book... paraphrased

    The Hamiltonian for the atom will have operators that only operate on the coordinates of the particular particles, but it also includes motion of the atom as a whole (the center of mass).

    So the Schrodinger equation may be separated, and the eigenfunctions connected only through a common separation constant, which includes the kinetic energy of the center of mass of the atom.

    So unless the atom is "in a box", the KE can assume any value, so the eigenfunctions are independent of each other, and the internal state of the atom is independent of the motion of its center of mass.

    In the event that the separation constant, itself, is quantized; the factors of the eigenfunctions may be only conditionally independent.
  13. Sep 25, 2013 #12


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    This changes nothing.

    I think it's because I can get to the heart of what you're asking a little easier than most since I'm kind of in the same boat as you.
  14. Sep 26, 2013 #13
    Crazy, it can’t be done.

    Consider the effect of the charges on the plates (while ignoring for the moment the repulsion of the two charged particles to each other).

    Positive plate [L] (located on the left) pushes a positron [A] to the right.
    Positive plate [R] (located on the right) pushes another positron to the left.
    When the positrons meet in the center we wish to apply lots of pressure so that they fuse together.
    You wish to bring the plates closer to each other (or increase the field strength) so that they cause the positrons to press against each other.

    Now move plate L towards plate R.

    As plate L approaches plate R, plate L begins to effect positron B.
    Plate L starts to push positron B to the right which is not what you want.
    Plate L approaching plate R starts to negate the effect of plate R from pushing positron B to the left.

    What you are asking is for plate L to only push positron A to the right, without affecting positron B, and that’s not possible. That’s not how fields work. The fields from multiple sources are superimposed upon one another, and you must consider the contribution from each source.

    A couple of ideas to get them (two positrons) together with great pressure...

    1: Put them both on the same plate with extremely strong negative charge.

    2: Collide them together at extremely high velocity.
  15. Sep 26, 2013 #14
    thanks for pointing out although I must admit that by now and before I knew you cannot just keep same polarity particles confined with two plates or whatever structures of the same potential.
    Well you could if you could make a sphere to have an electric field inside but since you cant it's a theory at best.

    @drakkith what do you mean by saying on the same boat , i'm just curious because I don't have an academic diploma in the fields i'm interested in yet I have high levels of enthusiasm and some brain powers and a hope of doing something worthwhile.

    By the way has anyone ever had some rough estimate of how high a potential difference corresponds to what levels of pressure? I guess it also varies by the gas you use etc but approximately?
  16. Sep 27, 2013 #15
    @drakkith , you kinda forgot about this thread for a while I guess:)

    @Mike Gomez , well I was thinking about protons more but it doesn't matter as long as it' s a charged particle etc.Colliding requires kinda large energies , beam focusing etc etc , involves scattering etc.
    The idea of using an extremely high electric field to literally confine a high density gas of particles is to my mind kinda better , if you can isolate the particles atleast from one potential so that they don' t form a current path and hence destroy the high potential difference which makes the field that keeps them pushed together is important.
  17. Sep 27, 2013 #16


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    It's not a theory if it's impossible.

    I have no degree either. I'm a freshman in college right now.
  18. Sep 27, 2013 #17
    What your studying ?
  19. Sep 27, 2013 #18


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    Astronomy. If you'd like to know more send me a pm so we don't get off topic.
  20. Sep 28, 2013 #19
    Maybe you are thinking of something like a large positively charged sphere, with an enclosed smaller neutral sphere located in the center. Now if we put positively charged particles inside, they (the free positively charged particles) will repel from the positive charge of the outer shell, but they will not be able to reach the center, and so they will be pressed against one another.

    So come to think of it, I guess my answer in post #13 “it can’t be done” is not completely correct. I was thinking in terms of only a few particles in the center of the sphere, and they would tend towards the center where the charges are balanced.

    However if you have trillions of these particles, then (even without a neutral sphere barrier in the center), not all of the particles will occupy the center of the sphere, and there will be a pressure applied to the particles which have a non-zero distance from the center.

    As to what happens to them when you press them together, I have no idea.


    About your question in post #1 regarding how the self field of a charge is affected, I don’t if much is known about that, but I think you should post that question in the “High Energy, Nuclear, Particle Physics” section. You might get some interesting replies.
  21. Sep 28, 2013 #20
    I think many of the people viewing that part of PF are also checking this one.
    As for the sphere and what you say , are you sure about that because a sphere has no net field inside of it as all the charge resides on the outer surface so will those particles feel anything being inside?

    Well even if they would that is just playing around to bring things into play for real we would have to use both positive and negative potentials.
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