Re: The Coulomb

[palmer@sfu.ca (Leigh Palmer)]

>     A chemist colleague asked me how the definition of the Coulomb unit
> came to be.  I know the "current" definition of the Coulomb is an AmpSec,
> but how did that develop historically?  Was there ever a time when an
> amount of charge was considered 'fundamental' and the current 'derived'?
> The AmpSec definition seems to me to be more conveniently reproduceable but
> less intuitive than a standard based on an agreed-on amount of charge.

I've always accepted the conventional explanation, that the coulomb is
the derived unit and the ampere is the more fundamental unit. Those of
us who entered college in the fifties were educated bilingually, using
both CGS and MKS units in electrostatics. (In cgs the electrostatic
charge is considered fundamental and current is the derived unit.)
There are other kinds of units, too, including a system called
electromagnetic units. My thesis advisor at Cal, Mike Tinkham, used to
refer to the system he called "GOU", or "God's Own Units". The late
Bob Karplus taught a graduate E & M course in rationalized CGS units!
I don't much like SI (I guess I am an atheist convert to GOU) but it
does have the virtue that it allows students to concentrate on learning
the concepts of physics rather than becoming obsessed with remembering
that there are 300 volts in a statvolt!

Leigh