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Electric and Magnetic Field Parallel

  1. Apr 22, 2015 #1
    1. The problem statement, all variables and given/known data
    f8fd9f8b40.png

    2. Relevant equations
    F=qE+qv x B

    3. The attempt at a solution

    The electric and magnetic fields are parallel, so the magnetic force will be in the j direction and the electrostatic force will be in the k direction. If the magnetic force was acting alone it would be cyclotron motion but since the electrostatic force is acting too does this mean it is moving in a helical path? I'm having some difficulty thinking about where the electric field is pointing and how to draw it properly. Thanks

    for part b) I can find the acceleration using (qE)/m and plug into a distance equation but im not sure if that is what I'm being asked to do.
     
    Last edited: Apr 22, 2015
  2. jcsd
  3. Apr 22, 2015 #2

    mfb

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    Sort of helical, as it is always accelerating in k-direction.
     
  4. Apr 22, 2015 #3
    Thanks. For part b, if I use v_0t+1/2*((qE/m))t^2 as the position of the proton along the z direction. Then for part c I can calculate the period and then put '3T' into the equation I found in part b to find the particles position. Am I on the right track with this?
     
  5. Apr 22, 2015 #4

    mfb

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    What is v_0 in z direction?
    Right.
     
  6. Apr 23, 2015 #5
    v_0 in the z direction is 0 so z=1/2*((qE/m))t^2 = 1/2* ((1.6x10^-10)(5000))/1.673x10^-27)*(1.3x10^-4)^2 = 4041m = 4km ?
     
  7. Apr 23, 2015 #6

    mfb

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    Is that the distance after one or after three revolutions?
     
  8. Apr 23, 2015 #7
    my mistake, that is one revolution so three should be 36431metres
     
  9. Apr 23, 2015 #8

    mfb

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    Right.
     
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