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Homework Help: Moving particles electrons and protons, using magnet to deflect fictional idea.

  1. Aug 1, 2011 #1
    1. The problem statement, all variables and given/known data

    An alien civilization has crossed the galaxy to invade the Earth and enslave humanity, again. Their attacks have been successful so far because their assault troops are equipped with handheld weapons that project beams of charged particles (protons & electrons) at very high speeds, able to melt or vaporize solid objects on contact. To counter this frightening weapon, the Earth Defense Force has developed a super-strength bar magnet that can be attached to a human soldier's helmet or weapon, so that its magnetic field will stop or deflect the charged particles.

    in order for the magnet to counter a beam being fired at a soldier from directly in front, how should the bar magnet be oriented?
    Should the N or the S pole be pointing directly forward?
    Or should it be vertical, and if so, should the N or the S pole point upward?
    Or won't this work at all?

    2. Relevant equations

    3. The attempt at a solution

    The magnet will help save the soldiers and the planet. By holding the magnet in front in a horizontal position. North and South from left to right in front of him holding it on his head where the magnet would be parallel to the gorund. This will create a magnetic field from the magnet spreading that will protect the soldier better. If he were to hold it vertically, the field wouldn't be protecting his lower body very well. What more can I say to this to help back my argument?
  2. jcsd
  3. Aug 1, 2011 #2
    You need to be thinking about how the magnetic field is going to affect charged particles, not how well the body of the soldier will be covered. (after all you can place a magnet anywhere, and the question also says it can be placed on the weapon of the soldier.)
  4. Aug 2, 2011 #3
    In order to counter the beam directly in front of the soldier, then the helmet would be the best place to put it I think. Horizontal would be ideal because the magnetic force should be strong enough to cover the entire body and the weapon too. So, this observed, I'm going to say that the particles will be perpendicular to the direction of the magnetic field when holding the magnet this way. When the particles meet the magnetic field they should give rise to a spiral trajectory out of harms way. Please give me more feedback to answer the questions.
  5. Aug 2, 2011 #4
    Well, you can have the field perpendicular to the direction of the incoming particles in two orientations (horizontal and vertical orientations), but they will cause the particles to circle in different directions. As a soldier, would you want them to be circling in your path, or out of it?
  6. Aug 2, 2011 #5
    I want them to circle out of my path, so how can I make that happen?
  7. Aug 2, 2011 #6
    Use the right hand rule - you know the direction of velocity (towards the soldier), and you want to send the particles out of the soldier's way. So you also know the direction of force you want. Find the direction of the magnetic field from this information, and you can then establish the best orientation.
  8. Aug 6, 2011 #7
    Okay, So using the right hand rule, i could point the bar magnet with North away from the soldier towards the oncoming particles. so this would cause the particles to spiral in front of the soldier and around the bar magnet, according to the right hand rule.
  9. Aug 9, 2011 #8
    That wouldn't deflect them out of the soldier's way though....they would still be in his path. The best configuration would be a vertical one.
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