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Effect on electron in magnetic field

  1. Oct 10, 2005 #1
    Here's a question that i'm quite confused about:

    A uniform constant magnetic field is directed into the page. An electron of constant mass and charge follows a clockwise spiral of decreasing radius path. Is the particle spead increasing or slowing down? and Why?
  2. jcsd
  3. Oct 10, 2005 #2
    try this

    I see two forces here (sort of, one is a consequense of the other):

    1st force (the real one): The electromagnetic force
    Look at what you have:
    B-field, velocity, charge (its an electron)

    2nd force (implied in the motion): Centripital Force
    What the first force is doing. Set the two equal. See what happens when you vary radius.

    Don't forget Centripital force= mass x centripital acceleration

    That should get you through the problem.

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