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Protons in a particle accelerator

  1. Apr 22, 2009 #1
    1. The problem statement, all variables and given/known data

    A very thin beam of protons is injected at non-relativistic
    velocities in a circular particle accelerator of radius R. The
    mass m and the charge e of the proton are known. The initial
    current in the accelerator is I and the total number of
    particles is n. The magnetic flux through the beam circuit
    changes at a rate of p Wb/s, while the radius of the beam
    track remains unaltered. What is the value of the current
    after one turn of the particles?

    2. Relevant equations

    emf = dflux/dt

    3. The attempt at a solution

    I'm not exactly sure if I have understood the problem correctly.
    But here is what I have got so far:
    emf = dflux/dt = p Volts

    protons passing per second = I/e

    since flux = BA, and A is constant, then B is changing.

    B=(mv)/Rq, so v of the particles must be changing.

    We are just learning about magnetic fields in class and I don't know how to put all the information together in this problems. I hope someone can at least point me in the right direction. Thanks!
  2. jcsd
  3. Apr 23, 2009 #2


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    Homework Helper

    I think the key here is that the radius of the beam in the accelerator doesn't change.

    From the relationship that R = (m*v)/(q*B) , if B is changing at p Wb/s then I think your velocity is changing at 1/p m/s isn't it?

    Since you have a fixed number of charges look at the effect on the time in making one circuit? (Charges per unit time being your current right?)
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