failing like never before


The Inverse Ohm

It seems to me that electromagnetics has a surprisingly large amount of funky terms and units, things like retarded potentials, hysteresis curves, Teslas, Ohms, Henrys, Webers and Siemens.

The authors (Hayt and Buck) of my electromagnetics textbook have a proclivity to inserting random historical tidbits into their books, probably in the hopes that it will help students to tie together seemingly random bits of technical information. So I wasn't surprised to come across a little bit of history behind conductivity when I was reading through my textbook. What I was surprised to find, was what initially appeared to be a typo; the book stated that the units of measurement for conductivity used to be the "mho" (but was now siemens). I immediately assumed that of course, the authors had meant to write "ohm" but had mixed a few letters about. But then I remembered that ohms are a measurement of resistance and after reading a few more sentences in the textbook, I learned that the "mho" is the inverse of the "ohm."

The best part, is that the symbol for "ohms" is an omega, and the symbol for "mhos" is an upside omega!!!

Brilliant. Absolutely brilliant.