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Homework Help: Moving Charges and Magnetism Problem

  1. Aug 16, 2014 #1
    1. The problem statement, all variables and given/known data

    Two particles A and B having equal charges +6C, after being accelerated through the same potential difference enter a region of uniform magnetic field and describe circular path of radii 2 and 3cm repectively. The ratio of mass of A and B is ______

    2. Relevant equations

    Force on the particle in a magnetic field = Bqv

    In a circular path, mv^2/r = Bqv
    →r = mv/Bq

    3. The attempt at a solution

    I don't know if I should consider their velocities to be equal.
    If the velocities are equal, the r(A)/r(B) = 2/3 which is incorrect.
  2. jcsd
  3. Aug 16, 2014 #2


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    Hello, anraphy. Welcome to PF!

    Do you know how to relate the final speed of a particle to the potential difference through which it is accelerated?
  4. Aug 16, 2014 #3
    Potential Difference and Velocity

    E = Vq
    →v = √(2Vq/m)

    V-potential difference
    m-mass of the particle
    v-velocity of the particle
    E-energy of the particle
    q-charge on the particle
  5. Aug 16, 2014 #4


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    OK. Good. Can you see how to use that?
  6. Aug 16, 2014 #5
    Hello, anraphy
    The particles have different masses but have equal charge.So when it's accelerated through same potential difference, they will gain equal electric energy=Vq=kinetic energy
    Similarly when entering in Magnetic field due to different velocities they will follow different circular path of radii ra,rb respectively.
    Last edited: Aug 16, 2014
  7. Aug 16, 2014 #6
    ImageUploadedByPhysics Forums1408248624.292973.jpg

    I think I got it. Thank You :)
  8. Aug 17, 2014 #7


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