[vox-tech] [OT] Electrical Engineering Question

[Peter Jay Salzman]

hi rod,

well, the math looks good, but you most likely knew that anyhow.

the relative error between 325 watts and 250 watts is about 23%.  pretty
high, imho.

the implicit assumption is that the dial's rotational speed increases
linearly with energy consumption.   i have no inner feeling for whether
that's true or not.  however, i can tell you that the power delivered by
an harmonic wave of any sort is proportional to the *square* of its
amplitude.  that's kind of counter intuitive, and was just meant to
illustrate that linear increase in angular speed may not result in
linear increase in consumed power.

but i'm _very_ interested in hearing PG&E's response to this.  please
send a followup to this when you have more info!

pete

ps- what kind of bulb consumes 250 watts?  a french fry lamp?   :)


begin Rod Roark <rod@sunsetsystems.com> 
> I got my first electric bill at the new house; looks too
> high.  So I decided to do an experiment.
> 
> Outside the house is an electric meter.  It reads KWH
> accumulated on 5 dials, and has a horizontal platter that
> appears to spin about 100 revolutions per KWH (anyone know
> if this is exactly true for a standard meter?).
> 
> So I figure that means 10 watt-hours per rev, or 36,000
> watt-seconds per rev.
> 
> I timed one revolution with most things in the house turned
> off.  45 seconds.  Then I turned on a 250W light bulb and
> timed it again.  32 seconds.  So:
> 
>   36,000 watt-secs / 45 secs =  800 watts
>   36,000 watt-secs / 32 secs = 1125 watts
> 
>   1125 - 800 = 325 watts -- for a 250W bulb.
> 
> How come?  Should I complain to PG&E, or is there some
> gotcha that I'm missing?
> 
> Thanks,
> 
> -- Rod
> 
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