Dear Bill and Jesse,
First, thank you Bill for responding to Jesse's question. I have to
admit that I ducked when he first proposed it as I have always found
it difficult to explain the difference between energy and power. I was
hoping that someone more knowledgeable about physics would jump in. I
particularly like Bill's line: power is instantaneous; energy requires
time (even if that time is only a picosecond) as better than the usual
dull definitions:
Energy is the ability to do work.
Power is the time rate of doing work or of using energy.
By the way, as I was searching for a better answer to Jesse's
question, I came across two interesting web sites. The first is the
USA Government Web at http://www.usa.gov/Citizen/Topics/Environment_Agriculture/Energy.shtml
where I found tutorials such as this http://www.glenbrook.k12.il.us/gbssci/phys/Class/energy/u5l1a.html
but I was not happy that these explained in suitable terms an answer
to Jesse's initial question. However, I soon became confused by the
diversity of measuring words used on this web site. As you know I have
found some 199 different words to describe energy (requiring 39 402
conversion factors) with old pre-metric measures, when only 1 unit is
needed for the metric system (with no conversion factors at all); see http://www.metricationmatters.com/docs/EnergyWords.pdf
On the way, I found this interesting comparison of energy sources http://physics.syr.edu/courses/modules/ENERGY/ENERGY_POLICY/tables.html
although I was disappointed in the muddled old pre-metric measures
placed in with the correct use of SI units.
Cheers,
Pat Naughtin
P.S. I shall mull some more!
On 2008/12/03, at 3:16 PM, Bill Potts wrote:
I agree with you Jesse.
5 W represents power and 5 J represents the energy used by a 5 W
device in 1
s.
Put another way, power is instantaneous; energy requires time (even
if that
time is only a picosecond).
Bill
________________________________
Bill Potts
WFP Consulting
Roseville, CA
http://metric1.org [SI Navigator]
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf
Of Ziser, Jesse
Sent: Tuesday, December 02, 2008 17:45
To: U.S. Metric Association
Subject: [USMA:42115] Re: Problems with power
--- Pat Naughtin <[EMAIL PROTECTED]> wrote:
supply the power needed - supply the energy needed (Again a difficult
idea as the engineers have to provide an electrical plant with a
power
rating that will provide the maximum amount of energy needed at a
particular time)
This in particular illustrates the problem I have with your use of
the term.
It sounds like
you're saying that a phrase like "supply the 5 watts of power needed
by the
motor" is incorrect
and it should be "supply the 5 watts of energy needed by the
motor". Is
that what you're saying?
Because this conflicts with the definition of the term "power" as I
learned
it in school.
And a power rating specifying the amount of energy needed at one
time? Well
that's just gibberish
to me.
Please explain in more detail why you think these uses of "power"
should be
changed. I am
confused.
Pat Naughtin
PO Box 305 Belmont 3216,
Geelong, Australia
Phone: 61 3 5241 2008
Metric system consultant, writer, and speaker, Pat Naughtin, has
helped thousands of people and hundreds of companies upgrade to the
modern metric system smoothly, quickly, and so economically that they
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for more metrication information, contact Pat at [EMAIL PROTECTED]
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