Velocity Selector (Problem 22.14)

   v =

The red dot represents a charged particle.
Enter a velocity and click "Set v" to set it. A uniform electric field is crossed with a uniform magnetic field
in the colored region. The magnetic field is directed out of the screen.

  • Click "Play" and observe the particle's trajectory in the colored region for different initial velocities.
  • Find the sign of the charge.
  • Find the direction of the electric field.

    Press "IN" to add a collimator, i.e. a narrow channel that absorbs all particles that strike it.
    You may remove the collimator by pressing "OUT".
  • Find the range of velocities for which particles make it through.

    Credits
    Authored by Kevork Spartalian, University of Vermont, based on Davidson College physlets.