Imagine the theoretical case where you have two coils "occupying the same plane" such that all the flux lines of one also go through the other. Or that they are wound on the same hi-mu toroid. No leakage inductance. Now suppose the two coils have a different number of windings, and therefore different self inductances. Since the mutual inductance L12=L21 cannot exceed the smaller of the two self inductances, this means k will have to be significantly less than 1. In simple circuit theory we tend to think of the coupling coefficient k as a measure of the degree to which the two coils are coupled. k=1 implies perfect coupling. In this case, despite the fact that there is perfect coupling, k<1. Where is the flaw in this somewhat over-simplified way of looking at coupled inductors? Perhaps |k|<=1 is allowed only when the two inductors have equal self inductances, and perfect coupling requies a smaller upper-bound on k when they aren't equal? There's a lot of published circuit theory that allows Lm > L1, even uses it in examples. But whoever said college professors know what they're talking about? Regards, Andy ------------------------------------------------------------------ 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 FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org 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