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John Cuthber

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John Cuthber last won the day on March 31

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About John Cuthber

  • Birthday 11/10/1965

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  1. If someone thinks you need an MSDS for the stuff you put on your food, they have failed to understand risk assessment.
  2. I think that part of the reason they use ferrocyanide is that it alters the crystal growth leading to a change in caking behaviour and also perhaps crystal form. Adding a little copper sulphate solution to the salt solution will form an insoluble copper ferrocyanide precipitate which you can filter off. People are still doing work on this sort of thing https://pubs.acs.org/doi/full/10.1021/cg201661y?mobileUi=0 It's a good idea to filter solutions before letting them crystallise, even if the best you can do it so filter through a paper tissue. However, I think the problem you have there is capillary creep. A couple of drops of cooking oil on the string above the level of the liquid may help keep the solution where it is meant to be.
  3. I found melting the platter with a blowtorch to be very satisfying. Ferric chloride attacks aluminium very vigorously. Be careful of the fumes released. It's probably best done outside. You might need to scratch through the magnetic layer to let the etchant get to the substrate.
  4. The standard way of depicting mirrors in a ray diagram is a line with shading on the "back" of it. https://en.wikipedia.org/wiki/Geometrical_optics#/media/File:Reflection_angles.svg Interestingly, the PIAB model works for a particle in the universe.
  5. Here is a page from Peter Atkins' book "Physical Chemistry" which refers to a particle in a box. The purpose of the box is to exclude the environment. It's as close to a free body diagram as anything else. He was a good lecturer, but his habit of producing new editions of the book was annoyingly good at dropping their re-sale value. That's why I still have mine from '84. When I was there, Oxon had the largest chemistry department in the Western world.
  6. I am curious. Studiot, when you got a hat pump installed, did you also upgrade the insulation?
  7. Not really. This circuit generates a distorted sine wave in which the phase of the distortion is arbitrary WRT the sine wave. https://en.wikipedia.org/wiki/Phase-fired_controller Obviously, you can resolve any arbitrary phase into a sin and cosine component. In that case, you only need two phases, as long as you don't mind one of the amplitudes being negative.
  8. How do I distinguish that from being fat? Also, it may have escaped your notice but essentially everyone is "peasant stock". However, that's enough time wasted on a random number generator.
  9. BMI is a system by which a doctor can tell a patient "You are too fat" while causing less offense. Reading anything more into it is fishy. It's a bit like IQ.
  10. Because it didn't make sense. BS1363 was introduced in 1947. It predates any EU standard. The UK BS1363 plug is wired with brown, blue and green/ yellow wires. The BRown wire goes to the Bottom Right pin. The BLue wire goes to the Bottom Left pin. Remarkably few people seem to understand this. There was a very old standard BS546 where the wires were black and red, but there's no good reason to revert to that . It went at about the same time as round-pin plugs. There was a relatively recent change of standard for wiring the socket that goes with that plug. Previously the house wiring was done with red, black and bare T&E cable. This was changed to match the colours used in the flex from the cable to the equipment. This was done deliberately; it was brought in at the same time as a requirement that any new installations needed to be verified by a competent electrician. Before that change, the "householder" could do their own work on the system. If you think about it you will see how they needed to change the wiring somehow in order to distinguish old wiring (which doesn't need a certificate) from new wiring (which does). The "old colours" cable is still available on eBay etc- it's not clear why...
  11. And if that dot is not in a direct straight line from the source and through the slit, then there's obviously diffraction happening. So we know that the single electron diffracts. So we know it's a wavelike thing.
  12. The Earth's rotation slows slightly when I go upstairs and rises again when I come back down. But the point remains that apart from the tiny effect of lifting some mass- that of the turbine and tower- using a wind turbine won't stop the earth rotating. Building the tower makes a difference, using it doesn't. If the wind didn't hit the tower then it would be slowed down by drag against the earth anyway. The rotation of the rock we are stood on changes. The rotation of the atmosphere also changes. But the rotation of the whole earth- including the geosphere and atmosphere pretty nearly doesn't. There's a tiny effect because, when the earth is nearer the sun, it warms and the atmosphere expands. The reason you can't use the rotation of the earth as a much better clock is that you only measure the rotation of part of it. If you could include the air as well, the whole earth would keep much better time.
  13. No. Not "tends to cancel" but "absolutely has to cancel". The Earth is pretty much isolated so the angular momentum is conserved. (Ignoring tidal coupling to the moon etc) Since the moment of inertia is also unchanged the rate of rotation can not change. Yes, the wind provides a torque on the turbine, but only because the planet provided a torque on the wind in the first place.
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