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Homework Help: A path that curves more sharply (e-)?

  1. Jul 22, 2014 #1
    1. The problem statement, all variables and given/known data
    Electron A is fired horizontally with speed 1.00 Mm/s into a region where a vertical magnetic field exists. Electron B is fired along the same path with speed 2.00 Mm/s. Which electron has a path that curves more sharply?
    A does.
    B does.
    The particles follow the same curved path.
    The particles continue to go straight.

    2. Relevant equations
    F=qv x B

    3. The attempt at a solution
    q and B for both are the same. The only difference is force and velocity. Because A has a smaller velocity, the force will be smaller; thus, the curve will be less sharp.

    However, this site says A curves more sharply. Site:

    I'm not understanding why...

    Thank you!!
  2. jcsd
  3. Jul 22, 2014 #2
  4. Jul 22, 2014 #3


    User Avatar

    Staff: Mentor

    No, see the bottom of page 37 of the PDF. Vacc is the accelerating voltage applied to the electrons.

    To solve this problem, work out the "Lamor Radius" of the circular motion of the electrons around the magnetic field lines. What are the equations of uniform circular motion in terms of velocity and centripital force?

    If you have trouble working it out, look up "Gyroradius" at wikipedia... :smile:
  5. Jul 22, 2014 #4
    wow stupid oversight on my part. Thanks so much!
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