[time-nuts] Modern motherboard with RS232 port

Chris Albertson albertson.chris at gmail.com
Sun Aug 19 20:16:08 UTC 2012

On Sun, Aug 19, 2012 at 12:19 PM, Tom Knox <actast at hotmail.com> wrote:

> Hi Ed;
> I may not have had enough coffee yet, but if Volt X Amps = Watts why would
> there be a difference?

That relationship holds for DC but with AC the phase relationship between
voltage and current depends of the complex impedance of the load.    If the
load is reactive the phase will not be exactly 90 degrees.  When we do the
math inour heads most of us always simplify and don't bother with complex
numbers but in real life impedance is complex.

But for simple back of envelope calculations we can pretend the power is DC
and just say Volt X Amps = Watts

Another simple way to know if your PC is going to cost you an arm and a leg
to run 24x7 is to place your hand over the cooling fan exhaust vent if hot
air is coming out you can know for sure that you are paying $$$ to heat
that air

Even if the PC consumes only 50W that works out to 438 KWH per year at 20
cents per KWH you can still pay for a new $100 Atom motherboard with the
savings in power and see a profit 2 years.

If gets worse in the summer if you need to run the AC.  Let's say the PC
burns 1W.  That dumps 1W of heat into the building and if your air
conditioning runs on a thermostat it will burn a little over 1W to remove
the extra heat.  The AC is a multiplier of the power used in the house.
 Using this logic someone at work figured out it was cost effective to
trash very old CRT monitor in the building.   Same for the light bulbs, we
pay a lot to cool the lighting load.
  (I would have simply installed windows that open and saved even more


Chris Albertson
Redondo Beach, California

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