On 2008/12/02, at 11:52 AM, Bill Hooper wrote:
Dear Bill,
Thanks for your comments. I have interspersed some remarks.
Overall, my concern is that the misuse of the two words, energy and
power, and of their two SI units, joule and watt, means that
discussions of subjects such as global warming, sea level rises, and
peak energy, can only be understood at the most primitive of levels.
To fully engage with these issues, I believe that we have to use
energy and power correctly as words and to use joules and watts
correctly as units. My fear is that many of our journalists and our
political leaders are not currently doing this. And I believe that the
scientific and engineering communities do our politicians a disservice
if they don't take a leading role on this issue.
On Nov 29 , at 10:43 PM, Pat Naughtin wrote:
... I simply didn't know what you meant by the word, power,
I don't think that I made an overstatement here. I simply meant that
as I read a news item and I arrive at the word, power, I have to pause
while I mentally explore what the writer might mean — just for a
moment, I don't know what the writer means.
Unfortunately, the word power has many different dictionary meanings
and non-technical people tend not to understand the difference
between one and another, or between power and energy.
I fully agree with you. I know of at least a dozen different meanings
apart from its technical meaning of 'the time rate of doing work or
expending energy'. At a deeper level, I think that non-technical
people also misunderstand, or don't know, that one of the meanings for
power is a technical definition that is defined in internationally
agreed standards; there is a qualitative difference between the idea
of power in 'the power of the people' and 'the power of my car'.
I think you'll find that (in the US, at least) the word power often
is used to mean "electricity". It is used to mean the providing of
electric service, whether that service is measured by the amount of
electrical energy or the rate of electrical power that is involved.
The same is true in Australia. The words have been so muddled for so
long that many if not most people use them incorrectly quite
regularly. This is true not only of the general public but also from
engineers who work in the energy industry, who one might think would
know better. Sadly, there is a tendency for some quite able technical
people to dumb down these words when they communicate with the public.
Seldom do people mean ANY particular measurable quantity of
electricity, whether it be amount of energy in joules, rate of
power* in watts, amount of electrical charge in coulombs, rate of
flow of charge in amperes, intensity of the electrical potential in
volts, or half a dozen other possibilities.
This is where the crux of the problem exists, I suppose. It is when an
engineer has to put a unit to a word that they then have to make a
decision about whether they are talking about energy or about power.
Of course this situation is not helped by the history of the
electrical industry where they eschew joules, kilojoules, megajoules,
etc in favor of kilowatt-hours, megawatt-hours, etc instead. The
presence of the word, watt, in these energy units clouds the issue
even further.
When electrical things cease working, people say "the power is out"
without ANY intended reference to the particular measured quantity
it is that has suddenly become zero. They just know things aren't
working.
True, again this is the same as in Australia.
That said, I agree that sometimes writers go the next step beyond
and use the word "power" to mean the amount of electrical energy
rather than the rate of electrical energy which is the technically
correct use of the word "power".
This is probably the key to the issue as far as a non-scientifically
trained politician is concerned. He possibly believes that global
warming could be reduced if only we decreased our use of power.
Regards,
Bill Hooper
Fernandina Beach, Florida, USA
==========================
SImplification Begins With SI.
==========================
*Some would argue that the word "power" already includes the concept
of "rate of ..." therefore it would be redundant or even wrong to
refer to "rate of power", as I did above. Thus, if power were
(correctly) measured in watts, then the rate of power would need to
be measured in watts per second. I'm not sure what that would be
unless perhaps it would be something like how fast a generating
plant could increase its power output from 10 MW to 500 MW, or
something.
Bill, I think that this paragraph explains why you are a physics
professor — and I am a farmer.
To go on:
The muddle between the meanings of the two words, energy and power, is
now so well established that there are various constructions that
would be difficult (perhaps impossible) to unwind.
Here are some examples — and a possible solution.
the power is out — the electricity is off.
generating power — converting energy. (Note: I think that this is
probably one of the hardest of these to change)
power station — energy conversion station.
power plant — work station (work, as used here, means the conversion
of one form of energy to another)
The words, power station and power plant possibly arose because the
engineers were constantly referring to the maximum 'power rating' of
the 'energy conversion station (or plant)' that they were currently
building. Especially if it was the biggest ever done for that type.
power needs — energy needs
power the world — provide the world's energy
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)
As you can see, some of these are more comfortable to use that others.
But the fact remains that confusion with the use of these words,
energy and power and their associated measuring units, inside the
scientific and engineering communities is not of much use to the
politicians who have to make real decisions for our real world of the
future.
Cheers,
Pat Naughtin
PO Box 305 Belmont 3216,
Geelong, Australia
Phone: 61 3 5241 2008
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