Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ames!vsi1!wyse!mips!vaso
From: vaso@mips.COM (Vaso Bovan)
Newsgroups: sci.electronics
Subject: Re: Tesla vs gauss, and other obscure units
Message-ID: <30542@buckaroo.mips.COM>
Date: 1 Nov 89 06:39:30 GMT
References: <30339@buckaroo.mips.COM> <1914@sactoh0.UUCP> <5817@shlump.nac.dec.com> <14184@jumbo.dec.com>
Reply-To: vaso@mips.COM (Vaso Bovan)
Organization: MIPS Computer Systems, Sunnyvale, CA
Lines: 35

In article <14184@jumbo.dec.com> dillon@jumbo.dec.com (John Dillon) writes:
>In article <5817@shlump.nac.dec.com>, koning@koning.dec.com (Paul Koning) writes:
>> 
>> Tesla is the SI unit, gauss the (officially obsolete) unit from the
>> CGS system.  Why is it still used?  Partly because we're in the USA,
>> where the metric system is only barely understood.  Partly because
>> engineers and amateurs tend not to care much about consistency in
>> units.
>
>Ahh, unit bigotry!  Just what we need.  The author suggests that 
>SI units are the answer regardless of the question.
>
>It is true that several systems of units carry an enormous burden 
>of historical chaos, but the CGS system is NOT one of them.  In fact, 
>were it not for the burden of real-life test instruments calibrated 
>in volts and amps, a person seriously schooled in classical 
>electrodynamics would choose to work in either the CGS or 
>Heaviside-Lorentz systems*.  If you wish to explore this further, 
>I would suggest reading J.D. Jackson's "Classical Electrodynamics", 
>which has an excellent appendix on units and dimensions.
>
>-- John

Which CGS system do you prefer: electromagnetic or electrostatic ?  Should
I have to remember that 1 abvolt = 10^-8 practical volts and 1 abampere
= 10 practical amperes ?  Or is easier that 1 stat volt = 300 practical volts,
and 1 stat ampere = (1/3)10^-9 practical amperes ?  Which system do you
recommend ?

>
>* extra credit question: do you know why the vacuum permeability 
>in rationalized MKSA (a subset of SI) is exactly 4*pi*1e-7 ?  

For bonus points, explain why the CGS electromagnetic unit of capacitance
is the gigafarad.