Wikipedia:Reference desk/Archives/Science/2020 July 21

= July 21 =

Charge in electric field

 * I thought the static electricity within a resistor caused the same charge displacement as the static electricity within a capacitor. + on one side, - on the other.  That way, a charge can gain electronvolts as it travels toward a sliding contact.  If the charge imbalance is in the form of the molecules within a resistor becoming dipoles, how would the dipoles add electronvolts to a free electron before the electron enters the sliding contact?  An electron that comes from infinity, accelerates toward a + charge in a dipole, and then passes by the - charge, and then continues to travel toward infinity does not have a net gain of energy.  — Preceding unsigned comment added by Vze2wgsm1 (talk • contribs) 02:39, 24 July 2020 (UTC)
 * I have added a header to your query. I will state that if you have molecules that are dipoles, they will rotate in an electric field, but will not actually conduct electricity. So they will not be part of a resister. Ions or electron can gain energy (measured in electron volts) if they are travelling in a vacuum with an electric field, but this will not be the case in a resister, the kinetic energy of the moving charge will be minuscule, and the energy rapidly converted to heat. Graeme Bartlett (talk) 07:52, 26 July 2020 (UTC)


 * I think you just said: KE will be miniscule, because KE converts into heat. I am not saying you are wrong.  I thought that on a molecular scale, charged particle collisions can be frictionless.  For example: Via the triboelectric effect, a chemical reaction can transport a charge from one side of a balloon to the other.  Because of the energy balance within a chemical reaction, I assume that reaction energy equals charge displacement energy.  Bottom line: frictionless movement of a charge to the other side of a balloon.  Vze2wgsm1 (talk) 21:19, 28 July 2020 (UTC)


 * There is neither static electricity nor charge displacement in a resistor and a capacitor doesn't produce a separation of charges, minus here and plus there. And electrons do not gain any energy in a resistor, but they lose some; you have already been said that. So do you have a 1) new and 2) meaningful question? Otherwise I think we should not waste any more time. 2003:F5:6F0C:9500:3859:69F1:7060:34C3 (talk) 13:30, 26 July 2020 (UTC) Marco PB


 * I see 2 claims: “There is neither static electricity nor charge displacement in a resistor … “ and: “And electrons do not gain any energy in a resistor, but they lose some:” If true, I hope you win the Nobel.  Note: The sliding contact on a potentiometer is a place of conversion of static electricity to or from magnetic energy.  The rules for conversion of static electricity into magnetic energy differ from the rules for converting static electricity into thermal energy.  Vze2wgsm1 (talk) 21:19, 28 July 2020 (UTC)
 * "The sliding contact on a potentiometer is a place of conversion of static electricity to or from magnetic energy." Bullshit. While I am sure that you personally are a fine person with higher-than-average intelligence, your theory as to how a potentiometer works is just plain silly, and you obviously are here to lecture us on how we are all wrong rather than being here to ask a good-faith question and learn something from the answers you get. --Guy Macon (talk) 21:48, 28 July 2020 (UTC)


 * Objects with static electricity cannot discharge each other unless they were within a CLOSED CIRCUIT. Otherwise, the pellets within a box of Styrofoam pellets would discharge each other.  Vze2wgsm1 (talk) 22:02, 28 July 2020 (UTC)


 * Go away, troll. --Guy Macon (talk) 22:17, 28 July 2020 (UTC)

What disease was in the Greek camp at Troy?
Supposing Homer’s description of the plague during the Trojan war were accurate,(except probably not being caused by Apollo’s arrows), then given that it attacked “mules first and dogs”(Cowper) and soldiers later, and it occurred around 1200bce on Turkish coast, what diseases might it have been? The Plague, or malaria, or mumps or what? I should have said also that after 10 days the Greeks were concerned enough to have a big meeting about it. Does this information help enough to at least eliminate some possible diseases?Rich (talk) 04:48, 21 July 2020 (UTC)
 * Of course it is not known. But see https://pubmed.ncbi.nlm.nih.gov/25551854/ for speculation. Graeme Bartlett (talk) 07:44, 21 July 2020 (UTC)

Is there a webpage that shows which taxons live in and/or can live in place X or Y but not both?
So you can find out things like what animal ranges/gardening plants/native/introduced species are/could be in Boston but not DC. Also I've seen maps of "plantal latitude" and "plantal longitude" and range map dumps of thousands of taxa (and there are species in the same genus with very different range limits) but not a "plantal coordinates" ordered list preferably pruned to a less huge size to include only the most useful ones, like how fossils that appeared and/or extincted quicker than average and are common enough to become an index fossil are collected into lists for geological dating. Sagittarian Milky Way (talk) 16:12, 21 July 2020 (UTC)
 * All species are introduced species on a long enough time scale. Also, Boston and DC are not different enough ecosystems to have distinctly different flora or fauna around them.  They will have much more in common than different; I would expect to find broadly similar flora and fauna, with perhaps a few small differences.  -- Jayron 32 16:52, 21 July 2020 (UTC)
 * Well introduced by humans, there's still some fuzziness as the original homes of some species if pre-man had never split from pre-chimps aren't well pinned down. That's my guess too, I'm wondering about the possible small differences. If red imported fire ants have a fairly sharp ecotone around the 10 Fahrenheit line (possibly north of Washington) then minor differences don't prevent intervening ecotones. Sagittarian Milky Way (talk) 15:40, 22 July 2020 (UTC)

Commercial bottled water has condensation near the top
I have bottles of water (think of a name brand) on a kitchen shelf at room temperature. It's summer, and some of these bottles now have condensation on the inside walls near the top of the bottles. Is this a sign of leakage or just water evaporating (quite a few dewdrops though) and condensing? Thank you. 104.162.197.70 (talk) 17:14, 21 July 2020 (UTC)


 * This is normal. If you place the bottles in a room where the temperature never changes (I noticed this in a clean-room where the temperature is controlled to well under a tenth of a degree) you see zero condensation. If the room temperature does change then whenever the air temperature is lower -- even slightly lower -- than the water, water evaporates from the (warmer) surface of the liquid and condenses on the (cooler) walls.


 * You might notice that when the opposite happens -- the liquid is cooler than the air -- you get condensation on the outside of the bottle. It takes a larger temperature change, though, because the outside air isn't at 100% relative humidity the way the air inside the bottle is. --Guy Macon (talk) 22:00, 21 July 2020 (UTC)


 * Additionally, see vapor pressure. The vapor pressure of a liquid is related (though not linearly) to the ambient temperature. Change the temperature, and you will change the portion of molecules in the bottle that are in the liquid phase and the vapor phase. So, increase the vapor pressure (via temperature), and you will have some of the liquid become a gas. Decrease the vapor pressure, and some of that gas will re-condense into a liquid. If the temperature is held perfectly steady, and the bottle contents were at equilibrium from the start, and you would not see that condensation. But, through temperature variations, you will change the equilibrium of the contents. If your kitchen is like my apartment, then in the summer, the temperature variation is greater than during other times of the year. My heating system can easily keep up with winter cold, but my AC can't keep fully up with summer heat, so during the day the temperature increases somewhat as the outside gets hot, and then decreases some as the outside cools enough for the AC to catch up. --OuroborosCobra (talk) 23:19, 21 July 2020 (UTC)


 * P.S. this is a really great question and a really great thought experiment! I might make a practice problem for my chemistry students modeled after this. --OuroborosCobra (talk) 23:20, 21 July 2020 (UTC)


 * Great answers and glad to help out a teacher. So if you have a closed bottle and enough time the air inside will be saturated? 104.162.197.70 (talk) 22:09, 22 July 2020 (UTC)


 * Yes. And "enough time" happens a couple of minutes after the bottle leaves the machine that puts on the cap. --Guy Macon (talk) 22:33, 22 July 2020 (UTC)