Paul, flux density and current are analagous. For the wires in a solenoid configuration, ( current coming out of the page ): < high density o > low density due to cancellation < o > high density In a microstrip the return current in the plane is into the page: low >>>>>>>>> oooooooooo <<<<<<<<< high <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> low Regards, Steve. Paul Levin wrote: > Dear SI-LIST'ers, > > I'm working on a presentation to explain transmission line to > non-engineers and I > find myself stumbling over some of the basics. (There's nothing like > explaining > something to bring out all of the glitches in what you were sure you > understood!) > I'm hoping that one of you may be able to supply the missing link. > > Nearly two hundred years ago Oersted and Ampere figured out that if you > have > two conductors carrying current in the same direction, they would would > to pull > in close to each other whereas if you had two conductors carrying > current in > opposite directions, they would want to separate. > > If one were to apply just these observations to microstrip, you would > expect to > see all of the trace current bunched on the side away from the ground > plane and > the return plane current in two bunches to either side of the trace and > as far away > from the trace as possible, if not on the bottom. > > Of course, this is almost exactly opposite from what we know happens. > > What is the force that overcomes Oersted and Ampere and causes the trace and > return currents to be so heavily attracted to each other? > > Thank you in advance. > > Regards, > > Paul Levin > Senior Principal Engineer > Xyratex > > > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > //www.freelists.org/webpage/si-list > > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > List technical documents are available at: > http://www.si-list.net > > List archives are viewable at: > //www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > > > > > -- Steve Weir Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 California office (408) 884-3985 Business (707) 780-1951 Fax Main office (401) 284-1827 Business (401) 284-1840 Fax Oregon office (503) 430-1065 Business (503) 430-1285 Fax http://www.teraspeed.com This e-mail contains proprietary and confidential intellectual property of Teraspeed Consulting Group LLC ------------------------------------------------------------------------------------------------------ Teraspeed(R) is the registered service mark of Teraspeed Consulting Group LLC ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu