Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Magnetic Force problem

  1. Oct 17, 2005 #1

    What is the radius of the smallest possible circular orbit that a 2MeV proton can have in a 2 T magnetic field?

    Answer (what I've got so far, at least):

    I assume that r = mv/qB is the formula I use for this problem, due to being given mass, B, q and all that, but I can't figure out how to apply it. I assume that v sould be replaced with an equation, but I cannot find that equation.

    Plus, it doesn't appear that there can be a "smallest" radius because as long as v is above zero, there will be a radius, but v can get infinitely small.

    Any suggestions?
  2. jcsd
  3. Oct 17, 2005 #2

    James R

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    The 2 MeV is the kinetic energy of the proton. So, you can work out the velocity v of the proton from the kinetic energy. You also know the charge q on a proton, and you're given B. You'll need the proton mass m, too.

    In calculating v, you'll need to convert the energy in MeV into an energy in Joules.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook