Wikipedia:Reference desk/Archives/Science/2018 August 11
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August 11[edit]
Consequence of the ideal gas law?[edit]
Could one say (using some sources if really needed) that the Nernst equation is a (logical) consequence of the ideal gas law, that can be easily deduced?--213.233.84.55 (talk) 15:59, 11 August 2018 (UTC)
- Nernst equation resembles the equation for the Gibbs energy for ideal gas but I doubt that you can logically derive the former from the latter. Ruslik_Zero 20:28, 11 August 2018 (UTC)
- No, neither is the consequence of the other, the best way to think of them is that they are both consequences of statistical thermodynamics, i.e. the connection between temperature and energy. You may have noticed that "R" (the universal gas constant) appears in both equations. R itself is not really a fundamental constant, it is derived from the Boltzmann constant (k), which is simply the relationship between temperature and energy; any time you'll be taking a temperature measurement and using it to calculate an energy, the Boltzmann constant is the conversion factor between what you can measure (temperature) and an abstract concept you can never directly measure (energy). You use "k" (the Boltmann constant) when you want energy per particle and you use "R" (the universal gas constant) when you want the energy per mole of particles. The quantity nRT has units of energy, as does the quantity PV, so that's the ideal gas equation. In the Nernst equation, you need units of volts, and a volt is a Joule per Coulomb (a volt is the motive force a mole of electrons has, Joule is energy, and a Coulomb is the charge carried by a mole of electrons). That's where the R comes into play there; the RT/zF gives you the unit of volts, which you need to add/subtract from the standard cell voltage based on how far off from equilibrium (the Q) your actual cell is. Just remember any calculation where the fundamental principal is based on energy, but you can only measure temperature, will have R show up somewhere. --Jayron32 21:19, 11 August 2018 (UTC)
weather averages[edit]
Why, in Los Angeles, is August (2 months after the solstice) the hottest average month, while December (the month of the solstice) the coolest average month (https://wxch.nl/2ntZXP2)?
- According to these tables, in LA July ist just as hot as August and Januar and Februar are both cooler than December: https://www.holiday-weather.com/los_angeles/averages/ 194.174.76.21 (talk) 12:09, 15 August 2018 (UTC) Marco Pagliero Berlin
- It's all to do with temperature lag which varies from place to place. June was certainly hottest where I live. Dbfirs 16:33, 11 August 2018 (UTC)
- There is also a seasonal change in the direction of the weather pattern in the Southwest that begins typically 2nd week of July and lasts about 6 weeks -- known as "monsoon season" where I come from. Although it primarily affects AZ & NM, it might presumably alter weather in CA to some degree°. Unsigned post, not by Akld_guy. -- OOPS! That would be me → 107.15.157.44 (talk) 09:53, 12 August 2018 (UTC) ... Wonder why auto-sign-bot didn't catch that
- Allowing for the different hemisphere, the same thing happens here in Auckland, New Zealand. The weather warms up in October and November as we come out of winter, then about mid-December it goes noticeably cooler. Usually there is cold, stormy weather around New Years, including snowfalls in the mountains 150 miles south of here, and we might have to put on our coats for a few days. This is not what you'd expect in mid-summer. Then, the hottest part of the year follows from mid-January to mid-February. Why? My WP:OR reasoning is that Auckland is at a certain latitude where the sun passes overhead and actually goes south (think north in your hemisphere) around the solstice. Thus, there are two warm peaks, the first as the sun is rising higher and higher in October-November, then a cooling as it goes south, and finally a reheat during January-February as it passes overhead again on its way north. Confirmation might be implied by the fact that Christchurch, far to the south of me, gets one summer peak, not two, which is centered on the solstice. Los Angeles and Auckland are both harbour cities, which may mean a more rapid cooling between the two peaks than in inland cities. Akld guy (talk) 05:34, 12 August 2018 (UTC)
Element/Fire Stryker fire extinguisher[edit]
This product caught my eye. At first I thought that the Element and the Fire Stryker were the same product, but the following YouTube videos show wildly different performance -- and no manufacturer tells a fib on a YouTube demo video, right? :(
- http://www.desert-wolf.com/dw/products/fire-and-rescue/fire-extinguishers/fire-stryker-portable.html
The other thing I noticed was that Element seems to be really vague on the topic of what chemical they use.
Does anyone have any information on this technology? --Guy Macon (talk) 22:17, 11 August 2018 (UTC)