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Homework Help: Magnetic Force, Electric Force

  1. Sep 29, 2010 #1
    1. The problem statement, all variables and given/known data
    24. A uniform magnetic field is in the positive z direction. A positively charged particle is moving in the positive x direction through the field. The net force on the particle can be made zero by applying an electric field in what direction?
    A. Positive y
    B. Negative y
    C. Positive x
    D. Negative x
    E. Positive z

    2. Relevant equations

    F = q* (vxB)
    F = q*E

    3. The attempt at a solution

    The answer for this problem is given and in my book it's given as B. However, I keep getting A. I don't know where I'm going wrong.

    So if the positive particle is moving in the positive x-direction and the B-field is in the positive z direction, then the resulting magnetic force is in the negative y-direction. And if we want a net force of zero on this positive particle, then it seems like if we apply an electric field in the positive y direction then we could get the net zero force that we're looking for. Is this an incorrect explanation?
  2. jcsd
  3. Sep 29, 2010 #2


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    Science Advisor

    I agree with you. I think the book is wrong. Anyone else?
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