Barbara, Magnetic permeability varies with many factors like flux density, magnetization, polarization and temperature. Actually it's the slope dB/dH of the B-H curve of that material. It's relatively easier to just talk about the initial permeability (B< 10 gauss) at a particular temperature, but still I've never heard about the existence of a mathematical function. If you want to get an idea of how Ui varies with freqency, you may look at a magnetic core supplier's catalog (Magnetic Inc., AVX, Philips, Siemens, Tokin, TDK, etc.). Of course it only tells ferromagnetic material's. I can send you some scanned pages if you want. K.K. Chin Artesyn Technologies, Fremont, CA http://www.artesyn.com Barbara Burcham <[log in to unmask]> on 05/12/2000 09:24:05 AM Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond to Barbara Burcham <[log in to unmask]> To: [log in to unmask] cc: (bcc: KK Chin) Subject: [TN] Formula for the Permability of Materials at different frequencies ? Formula for the Permability of Materials at different frequencies? Anyone out there have one of these that can be shared? Thanks, Barbara Burcham ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ############################################################## ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################