Re: [ATM] Go back to high school

["The Alarm Co. Llc." <tac@i1.net>]

----- Original Message ----- >
> Richard Schwartz wrote:
> Re: Go back to High School...
>> And take physics or electronics shop.  "Watts per hour" is a
>> meaningless concept.  Just plain "Watts" tells how much power the
>> electric company must deliver, and "Watt-hours" tells the total energy
>> cost of a cooking job.
>
>
> ***********************************

Well, not quite meaningless, it just doesn't mean quite what you seem to 
think.  The Watt is a unit of power, which is energy per time, or the rate 
of energy usage.  The Joule is a unit of energy.  1 watt =  1 joule / hour. 
So, a watt-hour (That's a dash, not a minus sign! It's a linguistic 
shorthand for multiplication.) equals 1 joule divided by 1 hour times 1 hour 
= 1 joule.  A Watt-hour is a Joule.
Now, a Watt DIVIDED by an hour is entirely different.  It doesn't have a 
specific name, but it it certainly a valid concept, namely, a rate of change 
in the rate of energy usage.  Think of it as the difference between speed 
and acceleration; a rate of movement vs a rate of change in the rate of 
movement.  This has a direct application to annealing.  The temperature of 
the glass must be reduced slowly, and so the power consumed by the kiln must 
be reduced over time.  The rate of this reduction could indeed be expressed 
in Watts per hour!  Now, in a relatively small kiln with relatively small 
chunks of glass, a suitable rate of cooling might be achieved by turning the 
power off completely and letting the kiln cool by convection and radiation. 
Not so with larger glasses.  I remember reading (decades ago!) about making 
the Mt. Palomar mirror, and how the kiln had to be kept heated for some 
amazing long time -- 24 months springs to mind, but don't quote me on that.

Best regards,
Bob
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