Talk:Specific energy

energy density vs. specific energy : any physical difference?
Both are measured in the same units. The same confusion seems to reign for specific power and power density. IMHO e.d. and s.e. are both being used interchangeably and should thus be merged (as in the power case). -- Kku (talk) 08:34, 6 July 2010 (UTC)


 * Depending on the words used, specific power is power per unit *mass*. Power density is power per unit *volume*. The thing is that the Wikipedia isn't a dictionary, articles are on the topic, not the words for the topic.


 * So the fact that the term 'specific power' might be used sometimes to talk about power per unit volume; that doesn't matter, power per unit volume goes in one article, and power per unit mass goes in another.- Wolfkeeper 12:53, 6 July 2010 (UTC)

Notational convention
The following statement was removed because it does not seem to be universal. At best it may be a convention adopted by some authors in some fields.
 * These intensive properties are each symbolized by using the lower case letter of the symbol for the corresponding extensive property, which is symbolized by a capital letter. For example, the extensive thermodynamic property enthalpy is symbolized by H; specific enthalpy is symbolized by h.  

If this is an official guideline of some institution, it should be presented as such. Note that such technical writing guidelines are never legally binding (nor even within the country where they may be issued) and authors are always free to follow or disregard them. --Jorge Stolfi (talk) 13:23, 24 February 2013 (UTC)

Reference list
A reference list showing a range of values for typical systems/substances would be useful here. For instance, the vanadium redox battery links here in an jnfobox, which implies that one could gain some sense of what the 10–20 Wh/kg means on this page (beyomd the obvious dimensional analysis. — Preceding unsigned comment added by 96.26.48.213 (talk) 13:33, 10 May 2014 (UTC)

External links modified
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Dimensionality of the mole
The mole isn't non-dimensional according to my understanding; it has units of mol. It's one of the SI base units. Saying it is non-dimensional is like saying that mass is non-dimensional because it depends on the mass of the international prototype kilogram in the same way the mole depends on the Avogadro constant. And, unlike the prototype kilogram, the Avogadro constant is defined in terms of the Planck constant and several other measured and defined quantities. Roches (talk) 22:37, 22 February 2016 (UTC)

specific impulse
I wonder if there should be mention of the related, but not quite the same, quantity: specific impulse. This is most commonly used in the case of rocket and jet engines. It is thrust*time/mass, or maybe more often, thrust*time/weight. The latter results in a quantity with units of time (s), in either metric or non-metric units. (More specifically, I believe the denominator is mass*standard g.) In the case of rockets, both fuel and oxidizer are included, for jet engines, only fuel is included. Gah4 (talk) 18:09, 3 June 2019 (UTC)