electro-Physics: 17.3409 volts

From: Tom Jennings <tomj_at_wps.com>
Date: Fri Dec 10 00:55:12 2004

I think in general "standard" voltages are utterly arbitrary,
at the him of mortals picking numbers they "like".

> 5V is popular because of TTL.

Probably the 60's TTL people could tell you why they chose that
particular number. If I had to guess, I'd say some design region
was around that voltage, and they arbitrarily rounded it off
for marketing purposes. 5.0 sounds so much more authoritative
than 5.2V or whatever. I doubt physics has much to do with it,
once the design region is chosen.

6v RTL etc is probably someone's favorite number, relating
to bad habits and dry cells. It sound so modern and portable!
(The hot electronics gadget in 1964? Pocket radio. As nifty as
a cellphone in 1998, seriously.)

> 12V is popular because it is a multiple of 2V, which is the voltage of
> lead battery.

It's actually not; lead-acid cells are 2.2V, and nominal is
13.7V, or 14.4, 12v is only a random point on the discharge or
load/internal resistance curve.

For things that ran on "dry cells" of the 1.52v variety there is
some correlation; go look at the portable radio electron tube
filament ratings, but they too are "nominal" due to internal
resistance and discharge.

A lot of these numbers got made up in WWII when lots of
sub-miniature dry-cell-powered things started to appear, as
multiples of 1.5V.
Received on Fri Dec 10 2004 - 00:55:12 GMT

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