Jump to content

John Cuthber

Resident Experts
  • Content Count

    17087
  • Joined

  • Last visited

  • Days Won

    30

Everything posted by John Cuthber

  1. You need to be able to prove that, rather than just claiming it. Otherwise you are not doing science. Then you should have no difficulty giving us an example. Please do so.
  2. The current rating is pretty much independent of the voltage. If the current is too high, the wire overheats and the insulation melts. If the wire is on the surface of the wall (unenclosed) then the heat can escape and the cable will carry more current before it overheats. If the cable is in an enclosed space like a conduit, there's less chance for heat to escape so, to stop it overheating, you have to ensure that the current is lower. As Swansont has pointed out, the derating can be complicated. It's best (In most places, it's a legal requirement) to ask an electrician.
  3. I think the best guess is attack by P4O10 vapour on the graphite. Homolytic thermolysis to give smaller molecules- notable P4O3 -is probably a feature too. But I doubt anyone really knows.
  4. Me. I would like you to change your posting style to one that isn't full of tosh. Thanks for asking.
  5. I'm now wondering what the least "hyped" version of putting that in context might be. How about "very expensive laser pulse dissipates as much energy as I do while sitting on the sofa for a minute or two."? Maybe "laser pulse equivalent to about half a teaspoonful of petrol"
  6. Laser pulse with "the energy from about 3 peanuts"* doesn't make quite the same impact. To me ,the impressive thing isn't the energy, but switching it on and off so quickly. * or something like that.
  7. Yes, but it works. https://en.wikipedia.org/wiki/Retr0bright I suspect that may be due to loss of plasticisers (by evaporation) and it would be practically impossible to reverse it. Also, rubbers are very susceptible to oxidation. I wouldn't try the peroxide trick on them unless I didn't care about making the problem worse. (In a "nothing to lose" scenario)
  8. To rhyme with rubles I presume... There's a reason why rubble has a double B. It's absurd; they are all bad attempts to reinvent this wheel;. ˈtrʌb(ə)l On the other hand, I gather that spelling contests are only national TV in anglophone countries... It's quite entertaining to get anyone- particularly a well educated native English speaker- to read this out loud. "I take it you already know Of tough and bough and cough and dough Others may stumble, but not you On hiccough, thorough, laugh, and through. And cork and work and card and ward And font and front and word and sword Well done! And now you wish, perhaps To learn of less familiar traps, Beware of heard, a dreadful word That looks like beard and sounds like bird. And dead: it’s said like bed, not bead– For goodness sakes don’t call it deed. Watch out for meat and great and threat, They rhyme with suite and straight and debt. A moth is not a moth in mother, Nor both in bother, broth in brother. And here is not a match for there, And dear and fear for bear and pear. And then there’s dose and rose and lose– Just look them up–and goose and choose, And do and go, then thwart and cart. Come, come, I’ve hardly made a start! A dreadful language? Man alive! I’d mastered it when I was five." We also have route pronounced the way Americans pronounce route and the two bits of equipment, a router and a router with different pronunciations. It depends if it's a modem like thingy where it's pronounced like roux; or a woodworking tool where it's pronounced like row.
  9. Well, if you carved the word from glass and polished it, then it would be clear. Or did you not realise that the word "clear" had two meanings? If you don't like Greek- fine; don't use it. It's absurd to complain that they didn't have a word for "energy"; nor did anyone else. Because there was no requirement for such a word. For some other words, like electron or entropy, we even know who coined the word. But - if they happened to be native Greek speakers, they could equally well have invented the word in Greek. The idea gets even sillier when you recognise that most of these new science words were actually invented in Latin. I doubt that your average roman soldier or Catholic priest had much call for a word for quantum in the technical sense it now has.
  10. if I was building a power company... But I'm building heaters. It's a bit like using a heat pump to heat the room- the "wasted" heat is still used so it isn't wasted and the overall efficiency is over 100% Though I have to admit the CoP is not as good as a conventional air source heat pump (by about 9 orders of magnitude) You don't need to explain things I already know. You need to explain to yourself what I'm seeking to achieve.
  11. Well, yes... One of them is impossible because mass/ energy is a conserved quantity. But, if you want to run a power station, what you need is a net release of heat. Burning coal is a net producer of heat, but the energy was already there as chemical energy- stored up from when it was solar energy
  12. OK. We need to sort something out. A single fusion event releases energy. Without the fusor, you wouldn't have that energy.. So, any fusor is a net producer of heat. If all you want to do is heat your house then, by using a fusor, you can put about 1KW of power in and get about 1.0000000001 KW of heat out of it. Obviously, that's not terribly economical- especially given the cost of heavy water. It's only really a very expensive toy. But it's a net producer. Presumably D T fusion.
  13. What's the evidence that it's not just some random numbers you (or someone) wrote down?
  14. Then you need to see a doctor, rather than asking questions about pH online.
  15. I'm really not a flat earther but... If the air was replaced by some gas with a slightly higher density and refractivity, you would be able to shine a light beam round the world. The air near the surface is denser than the air further up because of gravity. The air is thin at the tops of mountains etc. There's no argument bout that. And the refractive index rises with density. So light traveling through air near the ground is slightly slower than light going through air higher up. That means that a beam of light bends down slightly- it's a bit like a mirage https://en.wikipedia.org/wiki/Mirage In the right conditions, you could get the light beam to bend downwards at exactly the right rate to keep going round the world.. https://en.wikipedia.org/wiki/Novaya_Zemlya_effect
  16. That's a matter of perspective. You intend to dissolve gold. In fact it will dissolve a lot of metal oxides (zinc, iron etc) So you will use huge amounts of a moderately toxic chemical, mainly to dissolve stuff you don't want. Might still be an improvement on the use of mercury...
  17. 400 bar is 40 Mpa That's 40 MJ/ m3 or 40 KJ/ litre 25 litres per minute at that pressure is 40,000 * 25 i.e. 1 MJ/ min 16.7 KW of power at 100 % efficiency. At any credible efficiency it's not going to be the pressure that causes problems, but the temperature rise will set stuff on fire. What are you planning to do with about 20 horsepower of compressed air?
  18. What flow rate are you looking at? For a few ml/min you can use a 2nd hand HPLC pump. However, remember that a 6 KPSI liquid reservoir that bursts just spills oil and makes a bit of a mess, but a vessel containing air at that pressure is a bomb. The pressure won't affect the oil.
  19. Am I the only one wondering what happened to the rest of the Greek alphabet?
  20. I can't help wondering what Melania's definition is. I doubt we will ever know, which rather undermines this thread. They worked out the difference between friend and foe. Trump, on the other hand, has invented a difference between friend and friend so that nobody notices who the real foe is. As you say .
  21. At least "actually" isn't actually wrong.
  22. Why is that happening? Oh, I forgot, it's government policy. https://www.washingtonpost.com/blogs/answer-sheet/post/texas-gop-rejects-critical-thinking-skills-really/2012/07/08/gJQAHNpFXW_blog.html
  23. It's interesting that, as these are phased out, the same idea is being used to do a different job (on a smaller scale) https://en.wikipedia.org/wiki/Gas_holder
  24. Without collaboration is is rock solid certain that civilisation and technology would not develop. Competition is more or less the opposite of cooperation. The usual way to defeat bullies is not that bollocks about "standing up to them". (That just gets you beaten up) The solution is ganging up on the bullies. People who are given to cooperation are, therefore better placed to defeat bullies. So, for bullies to succeed, one thing they will seek to do is to reduce cooperation among those who they want to exert power over. A way of doing that is to set them in competition with eachother. So, for example, if you tell the low paid workers that their enemy isn't the billionaire but the immigrant... It's not an absolute thing- the best you can say is that encouraging collaboration drives down bullying and drives down competition.
  25. That seems unlikely given that breweries have been (carefully) using the same strains of yeasts for decades or more. However, if you needed a fresh supply, there's no need to trouble the animals, just wait a while with a bucket. https://www.jstor.org/stable/25031792?seq=1
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.