[time-nuts] Realization of electrical units (was: What everyday uses are there for accurate clocks?)

[Attila Kinali]

On Tue, 29 Nov 2022 22:02:19 +0000
Andy Talbot via time-nuts <time-nuts at lists.febo.com> wrote:

> The volt isn’t an SI unit. The amp is, and volts will be derived from amps
> via power which itself comes from mass, length and time.

While it is true that the SI unit is Ampère, the mise en pratique
for electrical units is done using a Josephson junction for the Volt
and a fractional Hal effect system for the Ohm. The Ampère is then
realized using a calibrated voltage and resistance. Why? Because
the Volt and Ohm can be accurately realized by quantum mechanical
systems that are impervious to small changes in their environment.
While the old definition of the Ampère was very hard to realize and
thus was never really used that way. This is also reflected in the
redefinition of 2019, which allows Volt and Ohm to be precisely calculated
using quantum mechanical relations and thus allow the for an exact
realization of the Ampère when going backwards.

But this is going into volt-nuts territory. Please ask there if
you want to know more.

			Attila Kinali

-- 
Science is made up of so many things that appear obvious 
after they are explained. -- Pardot Kynes