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I keep a record of our household energy use, last
year we used 186 GJ of energy for the whole year, combined natural gas and
electric, (Pat said the average was 150 GJ) mostly due to the poor
insulation of the house we live in. The highest use was in winter. Average
$20,23/GJ. Another reason I'd like to build a well insulated solar powered
house.
----- Original Message -----
Sent: Sunday, 08 January, 2006
23:25
Subject: [USMA:35609] Re: When was the
joule introduced to SI?
This
was my original note. I have collated the responses below.
Dear
All,
Can anyone give me the definitive date that
the joule was introduced into the SI as the unit for energy. I
suspect that it was at the same time as the newton, but Im having
trouble finding the right reference.
I have searched the BIPM
web site but with no
luck.
Dear All,
Many
thanks to everyone who contributed to my request for information about the
joule. Thanks for your help in tracing the official origins of the joule as
the unit for energy.
It seems that the chronology goes something like
this.
1818
James Prescott Joule (1818/1889) was born into a
wealthy brewing family in Salford, England.
1840
Joule stated
a physical law, now called Joule's Law, that heat is produced in an electrical
conductor.
1845
Joule was the first person to measure the
equivalence of work and heat, by having falling weights rotate paddles in
water.
At about this time, Joule shared in discovering the law of
the conservation of energy, which says that energy used up in one form
reappears in another form and is never lost. His co-workers were Hermann von
Helmholtz, Julius von Mayer, and William Thomson (1824/1907) (later Lord
Kelvin) and he worked with Lord Kelvin to develop the absolute scale of
temperature. Joule never claimed to have formulated a general Law of
Conservation of Energy but his experiments were certainly fundamental in
bringing about that formulation.
1881
At the First
International Electrical Congress (IEC) in Paris, five 'practical' electrical
units were defined; they were: the ohm, farad, volt, ampere, and coulomb. This
decision was based on the recommendations of a British Association for the
Advancement of Science and their recommendations were largely based on Joule's
researches on electrical energy. See an excellent article by Robert A. Nelson
at: http://www.aticourses.com/international_system_units.htm
on these and some other metric issues.
1889
In 1889, the year of
Joule's death, it seems likely that the British Association for the
Advancement of Science (BAAS) suggested the name for the energy unit to honor
the name of James Prescott Joule for his pioneering work on electricity and
energy. The BAAS promoted this idea actively and the Second Congress of the
International Electrical Conference (IEC) added the joule, watt, and a unit of
inductance that was later given the name henry.
The joule was
adopted by the IEC as the unit for energy and work. The Oxford Dictionary of
Weights and Measures quotes 'Le Système International d'Unités (Sevres;
France: Bureau International de Poids et Mesures, 1985)' as its
source.
1946
The joule was defined by the CIPM. (SI brochure,
Appendix 1, Section 2.4 (Electric current)), which shows CIPM resolution 2
giving the definition of the joule,
1948
The joule and its
definition were ratified by the CGPM as the official SI unit for energy. This
made the joule the official world unit for energy. Resolution 3 of the CGPM
(1948) said:
3.
The unit of quantity of heat is the joule.
They then went on to
say in a footnote:
Note:
It is requested that the results of calorimetric experiments be as far as
possible expressed in joules. If the experiments are made by comparison with
the rise of temperature of water (and that, for some reason, it is not
possible to avoid using the calorie), the information necessary for
conversion to joules must be provided. The CIPM, advised by the CCTC, should
prepare a table giving, in joules per degree, the most accurate values that
can be obtained from experiments on the specific heat of
water.
It seems that the CGPM felt troubled by the
promoters of the calorie (or is that Calorie) even then. (This footnote has a
decidedly grumpy tone in my opinion!)
1960
When the CGPM first
defined SI, in 1960, it included the joule as the derived unit for energy.
This reconfirmed the joule as the official SI metric unit for
energy.
1998
The joule is listed in 'The International System
of Units (SI) in 'Table 3. SI derived units with special names and symbols' as
the SI derived unit for the 'Derived quantity' of 'energy, work, quantity of
heat'.
2006
Question: Why am I researching the origin of the
joule?
Answer: Recently, I was rewriting my web page on why we
should move more quickly towards the metric system (See http://metricationmatters.com/why_metrication
), when I realised that a lack of knowledge about energy, and particularly
about how to measure it using joules, kilojoules, and megajoules etc., was
seriously hampering a great deal of public debate on extremely important
energy issues.
I wrote:
Energy and
power
This lack of ability of old measures to lead to
understanding can lead to very serious problems in the world. Consider the
world's pressing need to understand how we use our limited energy supplies and
how quickly we use them. These questions directly relate to global
warming.
Fundamental concepts such as energy and power are
essentially simple in concept but they often confuse politicians because of
the numerous ways they are measured with so many unrelated units. This
complexity makes it difficult, if not impossible, for politicians to
understand even basic quantitative information about the physical world around
them. To understand the total world energy issue using old measures is quite
difficult (even for scientists and engineers) and almost completely impossible
for politicians and the rest of us.
If you want to begin to
comprehend global warming, you need to have a working knowledge of most of
these 68 old pre-metric energy measures because in the year 2006 they are all
still in use:
Atomic energy unit, barrel oil equivalent, billion
electron volts, British thermal unit (16 °C), British thermal unit (4 °C),
British thermal unit (international), British thermal unit (ISO), British
thermal unit (IT), British thermal unit (mean), British thermal unit
(thermal), British thermal unit (thermochemical), calorie, calorie (16 °C),
calorie (20 °C), calorie (4 °C), calorie (diet kilocalorie), calorie (int.),
calorie (IT) (International Steam Table), calorie (mean), calorie
(thermochemical), Celsius heat unit (int.), coulomb volt, cubic centimetre
atmospheres, cubic foot atmospheres, cubic metre atmospheres, dutys, dyne
centimetres, electron volt, erg, foot-grains, foot-pound force, foot-poundal,
gigaelectronvolt, gram calorie, gram calories (mean), hartree, horsepower
hours, horsepower hours (metric), inch pound force, Kayser, kilocalorie (16
°C), kilocalorie (4 °C), kilocalorie (int.), kiloelectronvolt, kilogram
calories (int.), kilogram force metre, kilojoule, kiloton TNT equivalent,
kilowatt hour, kilowatt minute, kilowatt second, megaelectronvolt, megajoule,
megaton TNT equivalent, megawatt hours, newton metres, Q unit, quadrillion,
quad, Rydberg, therm (EC), therm (US), thermie (16 °C), ton TNT equivalent,
tonne coal equivalent, tonne oil equivalent, watt hour, and watt
second.
In contrast, using the metric system to consider energy
is relatively easy. We know that energy is measured in joules and that we will
probably need to use some large prefixes to understand our energy use on a
global scale. Here are some figures to consider.
If you are an
average teenager you will need 11 000 kilojoules or 11 megajoules of food
energy each day. This is 77 megajoules each week 330 MJ each month and
about 4000 MJ of energy for a whole year.
You might even like to think of
this as four gigajoules per annum (4 GJ/a) as there are 1000 megajoules in a
gigajoule. Even a hardworking construction worker only needs about 5
gigajoules per annum (5 GJ/a).
In a temperate climate, an average
family household uses a bit over 100 gigajoules of energy in a year. This
might go up to 150 GJ in a cold climate.
In 2003, the USA used
112 exajoules of energy that was made up from:
42
exajoules from petroleum,
26 exajoules from natural gas,
26 exajoules
from coal,
11 exajoules from nuclear energy, and
7 exajoules from
renewable energy.
See: http://metricationmatters.com/why_metrication
for more details about why we should move more rapidly to the metric units
expressed as 'The International System of Units
(SI).
Cheers,
Pat Naughtin ASM (NSAA), LCAMS (USMA)*
PO Box
305, Belmont, Geelong, Australia
Phone 61 3 5241 2008
Pat Naughtin is the editor of the free
online monthly newsletter, 'Metrication matters'.
You can subscribe by
going to http://www.metricationmatters.com/newsletter
*
Pat is the editor of the 'Numbers and measurement' chapter of the Australian
Government Publishing Service 'Style manual for writers, editors and
printers', he is an Accredited Speaking Member (ASM) with the National
Speakers Association of Australia, and a Lifetime Certified Advanced
Metrication Specialist (LCAMS) with the United States Metric Association. For
more information go to: http://metricationmatters.com
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