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Magnitude of the (perpendicular) magnetic field in the separator?

  1. Nov 1, 2006 #1
    ok so i'm working on a few problems on my physics homework and I got stuck:

    On the first one I answered the first question, but I don't know how to approach the 2nd and 3rd parts... what formulas would i use? and on the 2nd questions, I thought i needed more information than just the time, I thought i need like velocity of something is there a way to do the problem without velocity?

    1)A certain commercial mass spectrometer is used to separate uranium ions of mass 3.92 10-25 kg and charge 3.20 10-19 C from related species. The ions are accelerated through a potential difference of 50 kV and then pass into a uniform magnetic field, where they are bent in a path of radius 0.70 m. After traveling through 180° and passing through a slit of width 1.00 mm and height 1.00 cm, they are collected in a cup.

    (a) What is the magnitude of the (perpendicular) magnetic field in the separator?
    .5 T
    (b) If the machine is used to separate out 130 mg of material per hour, calculate the current of the desired ions in the machine.
    ?? A
    (c) In that case, calculate the thermal energy produced in the cup in 1.00 h.
    ?? J

    2)In the figure below, a charged particle moves into a region of uniform magnetic field , goes through half a circle, and then exits that region. The particle is either a proton or an electron (you must decide which). It spends 90 ns in the region.
    The image is a blue horseshoe shaped line entering the surface from the top on the right side and leaving the same way on the left, the magnetic field is pointed in ----> direction
    (a) What is the magnitude of ?
    ?? T
    (b) If the particle is sent back through the magnetic field (along the same initial path) but with 5.00 times its previous kinetic energy, how much time does it spend in the field during this trip?
    ?? ns

    Thank you so much,
  2. jcsd
  3. Nov 1, 2006 #2


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    See the annotations in the quote for #1.

    I'm not seeing the pidture for the second one, but it must be a semicircular path for the particle in the field. If the field stays the same and the velocity increases by a factor of 5, the force increases, but the momentum was greater to bgin with. Find the magnitude of the force and consider the centripetal motion.
    Last edited: Nov 1, 2006
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