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Force on Charge Moving in Magnetic Field

  1. Mar 8, 2009 #1
    A proton (mass mp), a deutron (m=2mp, Q = e), and an alpha particle (m = 4mp, Q = 2e) are accelerated by the same potential difference V and then enter a uniform magnetic field B, where they move in circular paths perpendicular to B. Determine the radius of the paths for the deuteron and alpha particle in terms of that for the proton.

    2. Relevant equations
    r = mv/qB

    r= radius
    B=magnetic field

    3. The attempt at a solution
    I thought V = delta PE = delta KE = delta (1/2)mv2

    And then I got confused.
  2. jcsd
  3. Mar 8, 2009 #2


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    Homework Helper

    When the charged particles are accelerated in a potential difference V,energy acquired by them is given by qV, where q is the charge on it. And it can be equated to its KE. First of all find the velocity of each particle and substitute in the formula for radius and compare them.
  4. Mar 8, 2009 #3
    Is the charge of a proton 1.6E-19 C?
  5. Mar 8, 2009 #4


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    Homework Helper

    Yes. But to solve this problem this value in not needed, because you are comparing radii.

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