FRICTION FORCES ON CHARGES MOVING OUTSIDE OF A CONDUCTOR DUE TO OHMS LAW HEATING INSIDE OF A CONDUCTOR

It is very well known and taught to undergraduate students of electrom agnetic theory that a charge e sitting at a height h above a conductor feels a force F-static = -(e(2)/4h(2))N, where N is a unit normal vec tor to the conductor surface. The static force is due to an induced co nductor charge density. Suppose (i) that the charged particle has a sm all velocity V parallel to the conductor surface, and (ii) that the in duced conductor currents obey Ohm's law with conductivity sigma. Ohm's law induced heating in the conductor then gives rise to a friction fo rce (over and above the static force) F-friction = -(e(2)/16 pi sigma h(3))V. A Simple derivation of this friction provides the undergraduat e student with an interesting physical example of an induced friction force acting at a distance, i.e., a charged particle moving in the vac uum can feel a friction force due to a neighboring conductor. (C) 1997 American Association of Physics Teachers.