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

Motion of Particle in a Magnetic Field

  1. Oct 24, 2004 #1
    F=q(v x B)
    If the velocity is in the i direction and the magnetic field is in the -k direction prove using Newtons Second Law that the trajectory of this charge must be circular?
     
  2. jcsd
  3. Oct 26, 2004 #2

    James R

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Consider the cross product first:

    [tex]i \times -k = j[/tex]

    Therefore, the force is in the j direction, perpendicular to the velocity. By Newton's 2nd law, the acceleration is in the same direction, perpendicular to the velocity at all times. Therefore, the force cannot change the magnitude of the velocity - only its direction. Since the acceleration has constant magnitude, the charge moves in a circle at constant speed.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?