John Cuthber
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Everything posted by John Cuthber
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It's longer. No. One "face" of the heated tip was connected to a length of tungsten rod that will have acted as a heat sink. I doubt that, It looks like a calculated adiabatic flame temperature, converted to the wrong units and with spurious accuracy. But you didn't use one. You didn't use tungsten, you used thoriated tungsten. How did you measure the attraction?
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How? How did you measure that temperature? How did you measure that?
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Science doesn't generally prove things. It sometimes proves that things are wrong.
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Given a product of two primes n, and n+2 the product is going to be very close to (n+1)^2 So you can take the nearest integer to the square root of the product, and the factors will be that +/- 1 Eg. imagine I give you the product 19043 the square root of that is 137.996... Very close to 138 And the integers 1 away from it are 137 and 139. And those are the factors of 19043.
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Alternatives to the World Health Organization
John Cuthber replied to ScienceNostalgia101's topic in Politics
The good news is that we are able to dismiss his views on the WHO. -
Alternatives to the World Health Organization
John Cuthber replied to ScienceNostalgia101's topic in Politics
So, we dismiss Trump out of hand - because he was so wrong about lots of things. And, on that basis- we know that his views are often wrong. So, for example, since he didn't like the WHO, we can reasonably deduce the the WHO is probably a good thing. -
I'm not sure, but I think that they rely on the fact that the aluminium corrodes faster in more acidic soils and thus sets free more electrons which pass through the meter and give a larger reading. Or they may work on a principle is similar to this. https://en.wikipedia.org/wiki/Antimony_electrode How would that help find out how the meter works?
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Does the world need to prepare for an economic crash soon?
John Cuthber replied to jimmydasaint's topic in Politics
Real men use nettles. -
Does the world need to prepare for an economic crash soon?
John Cuthber replied to jimmydasaint's topic in Politics
Panic buy toilet paper. -
A question about radiation from a microvawe oven
John Cuthber replied to Titus's topic in Classical Physics
You can. Most of the UK’s electricity is produced by burning fossil fuels, mainly natural gas (42% in 2016) from https://www.energy-uk.org.uk/our-work/generation/electricity-generation.html Fridges move moisture about, but they don't "produce" much. A lettuce doesn't steam as much as a roast. -
A question about radiation from a microvawe oven
John Cuthber replied to Titus's topic in Classical Physics
Is it a gas powered refrigerator? Most electric ones are practically airtight and don't give off moisture at all. -
Does stereotypical nerd or geek exists?
John Cuthber replied to CurseNight102's topic in Psychiatry and Psychology
I always wonder if that was meant to be ironic. It is, at root, a commentary on people... Nearer the topic; Someone once described the House of Lords as "A very civilised way to look after the elderly". I sometimes think that government research labs are a very civilised way to look after us nerds. -
A question about radiation from a microvawe oven
John Cuthber replied to Titus's topic in Classical Physics
No. -
I'm guessing at a typo. https://en.wikipedia.org/wiki/Overtone And the idea of "concordance" or "consonance" is cultural, not mathematical.
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The octaves are important- as Exchemist has explained. If two notes are in harmony then the octaves above them will also be in harmony. The division of the octave into 5, 8 or 12 (or more) is arbitrary and largely cultural. Having said that, there does seem to be something about the pentatonic scale that people all seem to "get".
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OK, imagine I get some sort of electrical generator- perhaps a Wilmshurst machine, and I put it on an insulating slab like a thick sheet of polythene or something. And I set it running (let's say it has a battery drive motor, and a remote control- so I can do that without anything being connected to Earth). such that it charges the two spheres - one positive and the other negative with respect to eachother. And then imagine that I bring an earthed wire near to one of the spheres. What do you think will happen? Not very, and not for long. It is generally quite conductive. It doesn't need to be. Static sparks are typically thousands of volts. The capacitances involved are of the order of pico farads. So even a bad earth connection with a resistance of 10 ohms would allow a current of hundreds of amps to flow. And that would discharge teh capacitor in a period of the order of a nanosecond or less. But for that to happen, the current would need to start and stop within a nanosecond. And that, in turn would mean that the rate of change of current was very large-hundreds of gigamps per second. And that could only happen if the inductance of the circuit was small enough. But to drive a rate of change of current of 100 GA/S with a few KV you need an inductance of about 10 pico Henries or less. And even a few inches of wire has much more inductance than that. So the thing that limits the discharge in electrostatics is generally the inductance, rather than the resistance. So... why did you point out the the resistance isn't all that low?
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And that is well within the range of typical static electricity. https://en.wikipedia.org/wiki/Static_electricity#Static_discharge You don't know much about this, do you? It isn't the charge that makes a difference, it is the voltage (though the two are related).
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True but: It's next to the two earthed metal screws that hold the cover in place, and you can make sparks by putting your finger near them. |It's also relatively thin plastic and may well conduct at the high voltages involved. And, of course, it may be a metal switch or a metal cover.
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sqrt(x)= -1 , no soln. ?
John Cuthber replied to IndianScientist's topic in Linear Algebra and Group Theory
By one convention, and by the other convention, both roots are considered as equally valid. For example, if you are solving a quadratic, you need to take account of both roots. https://en.wikipedia.org/wiki/Quadratic_equation -
sqrt(x)= -1 , no soln. ?
John Cuthber replied to IndianScientist's topic in Linear Algebra and Group Theory
I don't think this is an imaginary numbers problem. If the square root of x is minus one, then x = 1 is a solution. Root (1) = -1 -
Then you will have no difficulty proving it.