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Right Hand Rule

  1. Jul 30, 2012 #1

    s-f

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    I'm trying to solve problems about magnetic fields of electric currents induced by charged particles and wires. Most of these problems require the right hand rule, which I don't really understand. All I know is your thumb points in the direction of the current and your fingers curl in the direction of the magnetic field. I don't understand how to tell if the magnetic field is going into the page or out of the page based on this.

    Question 1: The figure shows 2 charged particles moving in opposite directions. What is the direction of the magnetic field at point P? I attempted to copy the figure but the forum keeps editing it so I'll describe it: there are 2 positive particles separated by a distance (d). One is moving to the right, the other to the left. Halfway between the particles is point P (kind of like below, the plus signs represent positive particles with P halfway between).

    (+)
    l
    l
    P
    l
    l
    (+)



    Answer: Both particles make magnetic fields that point into the page.

    I know this is the correct answer, but I don't get how to do this? How can you tell if the magnetic field is into or out of the page? :confused:
     
    Last edited: Jul 30, 2012
  2. jcsd
  3. Jul 30, 2012 #2

    vela

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    What specifically is it about applying the right-hand rule that is confusing you? Your textbook will likely give you as good of an explanation as you're going to get here.
     
  4. Jul 31, 2012 #3

    PeterO

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    Draw a line across your page,
    Now hold your hand with thumb pointing left, with that line directly under your thumb. Your fingers curl such that they will be curling into-the-page above your thumb - ie further up the page than the line - but out-of-the-page below our thumb - ie further down the page than the line.

    Turn your hand so that your thumb points right and you get out-of-the-page above your thumb, and into-the-page below your thumb.

    Point P is below a right moving charge [so its field is into the page] and above a left moving charge [so its field is also into the page]

    Net result is the field is into the page at P - the two fields reinforce rather than cancel each other.
     
  5. Jul 31, 2012 #4

    s-f

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    @vela - I don't have a textbook :/ I'm taking a 6 week summer class in which we have to cover a whole semester's worth of material. It's really fast-paced and we have to learn a lot of things on our own as there isn't enough time for the teacher to go through everything. But I looked at YouTube tutorials on the subject and it helped a lot to see someone demonstrate it because we didn't learn in class.

    @Peter - Thanks so much for explaining it really well! :)
     
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