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Homework Help: Magnetic force problem

  1. May 12, 2016 #1
    1. The problem statement, all variables and given/known data


    As shown in figure above, a conductor RS with 2 m length which is powered with currents is put in a 0.5 T magnetic field. If the force generated by the conductor is 1 N into-the-screen, then the magnitude and direction of the current in conductor is ...

    A. 1 A from R to S
    B. 1 A from S to R
    C. 2 A from R to S
    D. 2 A from S to R
    E. 5 A from R to S

    2. Relevant equations

    F = BIL sin θ

    3. The attempt at a solution

    1 = 0.5 I 2 sin 90°
    I = 1 Ampere

    And, the direction is from S to R
    (I point my 4 fingers to the right side, my palm inward, so the thumb (current) points upward)

    Is it correct?? I need to make sure about this... I'm self-studying :smile:
    Thanks in advance
  2. jcsd
  3. May 12, 2016 #2


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    PF isn't really good at stamp-approving exercises -- it doesn't really help you if we do and you're found wrong anyway.
    (It also antagonizes teachers in general :smile:).
    You actually need to convince yourself that what you did is correct (because you fully understand what you did, checked it, etc.).

    On the other hand, if I do the exercise I get the same result. I can't remember al these rules, but I can remember the Lorentz force $$\vec F_L = q\left (\vec E+\vec v\times\vec B\right )$$. And if I imagine a corkscrew and rotate ##\vec v## over the smallest angle to ##\vec B## I see that it goes into the page if ##\vec v## points from S to R

  4. May 12, 2016 #3
    Alright, thanks..
    Sometimes it's just hard to fully confident that it's 100% correct if I'm self-studying..
    Thank you for your response anyway :smile:
  5. May 12, 2016 #4


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    I believe you. Hats off & good luck !
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