title.gif (3164 bytes)

WebAssignment.gif (2865 bytes)

HarmonicMotionI.gif (2743 bytes)

  • Operation of a mass spectrometer.

  • Lorentz force.

  • Radial (centripetal) force
Topics:  Lorentz force, electromagnetism, radial (centripetal) force, mass spectroscopy.

Pre-requisite skills:  Elementary understanding of basic electrostatics and Newton's Second Law.

Approximate completion time:  Under 30 minutes.

Provide sufficient detail to verify that the assignment was completed in a meaningful manner.

MERLOT site:   Mass Spectrometer, by Tony Abou-Assaleh.  (direct link).

Applet by Tony Abou-Assaleh
1.  Familiarize yourself with the operation of the applet. Notice that there is a slider on your left for controlling the magnitude, and direction, of the external magnetic field.  

(a) Press the "Sweep B" button and observe the motion of this slider and the trajectory of the particle.  What happens to the motion when the slider passes its midway point, that is, when the field changes direction.

(b) Is the particle postively or negatively charged?   How do you know this?

2.   Now increase the speed of the charged particle.  Explain what happens to the radius of curvature of the charged particle.  

3.  Press the "Reverse B" button.  Notice that the field direction is now pointing into the page (away from you).  Run the applet and describe what changes in the motion of the charged particle.

Helpful Resources

  1. Mass Spectrometer by Angel Franco Garcia..
  2. Mass Spectrometer by Larry Gladney.
  3. Charged Particle Motion in E/M Field by Fu Kwun Hwang.
  4. Motion in an Electromagnetic Field by Mark Sutherland.
  5. Charged Particles Moving in a Magnetic Field by Sergey Kiselev

Return to Web Assignments