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Right Hand rule in regards to direction of velocity

  1. May 16, 2008 #1

    I am trying to figure out how to use the right hand rule when magnetic force points downward. I comprehend what the fingers are used for but when i but the finger downward I get a direction to the left, but the answer is that the direction is north. Why is that?
  2. jcsd
  3. May 16, 2008 #2
    The Right Hand Rule is used to determine the direction of the Magnetic Flux Generated by a current flowing through a wire wrapped around and and Iron Rod Core. If the fingers are curled around the rod in the direction of the current, The resulting Flux will be in the direction of the extended thumb. By convention we call that pole of the core "North".
  4. May 17, 2008 #3

    Doc Al

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    Staff: Mentor

    Please describe the exact problem you are trying to answer. (There are many right hand rules.)

    Since you mention magnetic force and velocity, I can guess that you are trying to find the direction of the magnetic field or velocity that will result in a downward force on some charged particle?
  5. May 19, 2008 #4

    You do cite the velocity, so...

    In the Right Hand Rule, the palm is the direction of the magnetic force, the four fingers are the direction of the magnetic field and the thumb is the direction of the velocity. If there is no angle written down for the velocity's direction, it is perpendicular to the magnetic field.

    If the magnetic force is down, then the palm faces down. By the way you describe it, the answer is that the velocity is in front, or towards the north, so if you twist your hand, the direction of the field is right, or east. Check your problem again to see if it doesn't say something about the directions again.
    Last edited: May 19, 2008
  6. May 19, 2008 #5
    The problem states that an electron has a downward force traveilling in a magnetic field west. So the hand is pointing down and the palm is pointing toward the left?
  7. May 20, 2008 #6

    Doc Al

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    Staff: Mentor

    Read this: The right-hand rule for magnetic force

    I recommend the middle right hand diagram, but any version will do. Don't forget to reverse things since the electron has a negative charge.
  8. May 21, 2008 #7
    If the magnetic field is west, the tips of your fingers would be pointing to the west (your left side) and the downward force means that your palm would be facing downwards.
  9. May 21, 2008 #8
    Ok I get the problem. I was visualizing the plane differently. Thanks
  10. May 22, 2008 #9
    the right hand rule is a simple method for determining the resultant direction of a cross product.

    that means, any time you have a cross product, the right hand rule is applicable.
    not just the specific case you described
  11. May 25, 2008 #10
    The way I thought of this was to imagine a compass on a Horizontal plane. With the fingers pointed to the west, and the palm facing down onto the plane, you should end up with your thumb pointing in the South direction. Note since this is an electron simply reverse the direction and you end up with the electron moving North.
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