Dear All,
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 I’m having trouble finding the right reference.
I have searched the BIPM web site but with no luck.
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,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).
26 exajoules from natural gas,
26 exajoules from coal,
11 exajoules from nuclear energy, and
7 exajoules from renewable energy.
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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