The electric and magnetic forces acting on an ion in uniform crossed fields are shown to add to give a centripetal force of constant magnitude, moving with the ion in a cycloid trajectory. A comparison is made with the analogous forces in the classical brachistrochrone case of a bead sliding down a frictionless cycloid-shaped wire.

This content is only available via PDF.
AAPT members receive access to the American Journal of Physics and The Physics Teacher as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.