[Archive!] Pure mathematics, physics, chemistry, etc.: brain-training problems not related to trade in any way - page 479
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This is quite obvious. Zero/unit are simply two different objects. And how can this understanding simplify the solution? Admit it already.
Nah, Alexey, don't get any funny ideas. The reaction is already steadily going on, the fire is blazing. And at the moment of Ch, we sharply cool the outside temperature - say, to -150 (let oxygen remain a gas). The layman, of course, will think that the fire will go out of action. But we are armed with the Le Chatelier principle...
Alexey, something reminded me of your problem, and I finally understood, where there is a discrepancy.
More specifically, there is a big difference between the phrases "cold material burns" and "burning material undergoes cooling".
In the first case, you're right, the Le Chatelier principle works like a charm, because it is expressed in the well-known Fourier law: the heat flux from the hotter region to the less heated region due to thermal conduction is directly proportional to the minus temperature gradient, plus there is also the heat transfer from the exothermic reaction to the unheated region. As a result, indeed, the colder the burning material is, the faster the reaction will spread.
But in the second case the situation is different. Suppose we have a steady-state combustion reaction, and at some point begin to cool it down, say, linearly in time. Note that the condition for the propagation of the reaction is that the heat released by the combustion of an element of volume dV is at least enough to heat up to the ignition temperature of the same volume of the neighboring element dV. Otherwise, the reaction rate will obviously decrease until the actual volume of burning material reaches zero, i.e. the fire is extinguished. This condition will not be fulfilled, however, when the temperature difference reaches a certain critical value (if it exists, i.e. above absolute zero - but it depends on the properties of the material).
Like this. The picture, of course, is simplified, but nevertheless quite plausible.
You got it right. Thank you.
Alexey, and thank you for your loyalty. But I'm going to take a rest from forum for a couple of months - I'm really tired of it - I'm coming here like to work, I'm explaining something to somebody, digging in codes, writing codes for somebody as if I really need it :) Maybe I appear in humour, books or music branches during this period... :) That's it, I'm resting!
Lol, it's been a while since you got banned...
A NEW CHALLENGE IN PHYSICS
.
A question for people who know how to think. Here' s a description of what I think is an interesting experiment - arc burning in water or electrolysis (whatever you want to call it). The funny thing is that the amount of energy that is released is clearly greater than the amount of energy that is consumed.
The question is: how is this possible?
My personal assumptions are:
1. No account of energy released by dissolving the metal of the electrode;
2. Not all the current passing through the wire is taken into account (the phenomenon of current impedance), the frequency of current consumption is higher than the mains frequency, the shape of current at this frequency - is not sinusoidal;
Please don't blame the author of this site - the road less traveled. Link to video.
A quote from a website:
Comrades, and now I'm going to write you the most extravagant *fucker from my maths homework! I'm in silent shock! I'm gonna call my teacher, I swear.
"14 kids were learning to swim. Three of them can't swim yet, and two of them... Drumroll...DON'T Drown (!!!). How many children have learned to swim and haven't drowned yet?"
A NEW CHALLENGE IN PHYSICS
.
A question for people who know how to think. Hereis a description of what I think is an interesting experiment - arc burning in water or electrolysis (whatever you want to call it). The funny thing is that the amount of energy that is released is clearly greater than the amount of energy that is consumed.
The question is: how is this possible?
My personal assumptions are:
1. No account of energy released by dissolving the metal of the electrode;
2. Not all the current passing through the wire is taken into account (the phenomenon of current impedance), the frequency of current consumption is higher than the mains frequency, the shape of current at this frequency - is not sinusoidal;
Please don't blame the author of this site - the road less traveled. Here is the link to the video.
Most likely the reason for the discrepancy is that the voltage is measured at the output of the autotransformer and the current is measured at the output of the bridge. As a result the power supplied is underestimated and you get the wrong efficiency.
Most likely the ammeter is lying: after the rectifier the author does not put smoothing circuits, so there is no direct current passing through the ammeter, but roughly speaking a sine wave folded in half, which, by the way, can also be, firstly, cut off at the tops of diodes, and secondly, have small negative areas, due to the negative cut-off voltage. The oscillating character of the current is confirmed by the description of the experiment, in particular the vibration of the vessel with water at high voltages.
Thus, if a DC ammeter is used, its reading is likely to be incorrect. To get the correct reading, the output of the bridge must be rectified in a human way.
alsu: ......... Таким образом, если используется амперметр постоянного тока, то его показания, скорее всего, неверны. Для получения правильных показаний следует по-человечески выпрямить выход моста.
i.e. use a high quality direct current source. Only with a high quality DC current (constant in both magnitude and direction) is it possible to accurately measure the power consumption of the system. What to use as electrodes in this case is not quite clear. Platinum? Carbon?
The question also arises: what does water have to do with high voltages at all? Can this effect be possible without water - in a gas environment, although it is more difficult to measure the amount of energy released there. One could probably try an experiment with an arc burning in a gas discharge lamp - fluorescent, mercury, neon, etc.