22 Jan
1999
22 Jan
'99
8:51 a.m.
On Jan 22, 19:16, Hans Franke wrote:
Subject: Re: OT: Alien Media (was Disasters and
Recovery)
Excuse me if I interupt, but you are talking about
measuring
a specific voltage. But thats completly independant from the
definition. Only if you want to define Volt based on some
specific reproduceable effect - but thats not necesaty. To
get all electrical units you just need the 7 basic SI units
(Length, Weight, Time, Current, Temperature, Brightnes (?)
and Mol (sorry, no idea how to translate Stoffmasse)) and
length metre m
mass kilogram kg
time second s
electric current ampere A
thermodynamic temperature kelvin K
luminous intensity candela cd
amount of substance mole mol
only one is an electric unit (the Ampere). And only
these
7 units have to be defined on specific, reproducable effects.
1V is defined as 1 kg m^2 / A s^2.
As Hans implies, all other units are derived from these seven (and the two
angular measures). But the volt is defined as kg m^2 / (A s^3) -- Hans
lost a "per second" (Hertzlos, I suppose ;-).
--
Pete Peter Turnbull
Dept. of Computer Science
University of York