41

Technology / Re: Why do electricity companies transmit power at very high voltages?

« on: 13/04/2016 17:25:23 »

i know that transmitting electricity at high voltages makes the mediums of transportation to be smaller, but how does the inductance an transformers correlates to this?   [] [] []

A transformer has relatively little inductance when it's carrying current; the secondary windings carry, in a sense, the same amount of 'current' around the iron core (specifically the amp-turns is nearly the same) and opposes the input side's inductance, and consequently transformers when carrying current have very low inductance.

When the output side isn't carrying current, the inductance goes really high, since the inductance on the input side isn't being opposed, and this means that the transformer then has high inductance, which means high impedance, and because it's high impedance, the input side ends up carrying relatively little current, so the resistive losses on the input side are small, and transformers are still fairly efficient when nothing is drawing current.

If that didn't happen, every time we turned off all the power in the house, the transformer at the substation would glow red hot!

So, a lot of the efficiency is about what happens when you're not using power as much as when you are.

Still, some power is still lost like that. Those 'fat' power supplies that you plug into the wall, they step the mains down to 12v or 5V. But even if they not carrying any current, if you touch them they're often slightly warm; that's the current that's not being blocked by the transformer's inductance. The modern slimline ones are much more clever, and the transformer inside is much smaller, and they disconnect the transformer from the mains when they're not in use, and so they are cold to the touch when they're not powering anything.

42

Technology / Re: Connect a Simple Circuit to a PC

« on: 06/03/2016 01:08:01 »

Get an arduino; they're much cheaper, they plug into a PC with a USB cable, and have plenty of IO pins, and can record the exact time that an event happens.

43

General Science / Re: How is the force between two magnets calculated?

« on: 17/12/2015 15:26:24 »

In the type of ranges showed in the picture, you can approximate each magnet with a magnetic moment, and get a fairly accurate estimate of the torque. This will probably fail though at closer range.

44

Plant Sciences, Zoology & Evolution / Re: Are white eggs no longer readily available in UK supermarkets?

« on: 12/12/2015 18:31:47 »

Chicken egg colours are genetically determined, you can get all different colours, red ones, green ones, olive ones, white, brown.

It doesn't affect the nutrition, nor does it necessarily indicate they're inbred.

It's just what variety of chickens are used to produce the eggs.

45

Technology / Re: Negate the expansion of freezing water using small, compressible balls

« on: 16/11/2015 16:35:38 »

I saw a device for use in pipes; you put a long plastic pipe inside the copper pipe, and then when the water freezes it squeezes down on the plastic and the copper pipe doesn't burst.

I don't see why in principle you couldn't do the same with a tank. Perhaps just putting some weighted fizzy drink bottles, or something similar, into the tank might stop it bursting.

I don't know that it's guaranteed to work though; it may critically depend on how the crystal structure forms each time as to whether it pushes on the plastic bottles or on the sides- ice shove is quit an impressively powerful phenomena.

46

Technology / Re: How can renewable energy farms provide 24-hour power?

« on: 30/10/2015 22:21:05 »

In the context of this thread, for storing renewable energy, it's primarily a question of cost. If it costs £0.1 per kWh that is stored, then it's unlikely to be widely deployed as representing a large percentage of our power, whereas at ~£0.01 per kWh, it becomes more or less a no brainer.

I believe the quinones they're planning to use are believed to be relatively benign; they're chemically closer to photosynthesis quinones. The real nasty with previous versions was the hydrobromic acid, but they've replaced it with potassium hydroxide; which is clearly corrosive, but probably wouldn't form WWI-style gas attack if a premises caught fire.

47

Technology / Re: Magnetic Powder Power?

« on: 14/10/2015 01:26:49 »

? Powder is usually poorly magnet; most magnets are solids.

A pile of powdered iron will attract a small magnet from quite a distance, but not at all strongly.

A pile of powdered neodymium or other hard magnetic material will probably not do so significantly, it will tend to arrange itself to cancel itself out

48

Science Experiments / Re: Will this experiment result in an overunity device?

« on: 07/10/2015 01:43:15 »

no

Your device is very, very well described by Newtonian Mechanics, and there's a general proof that overunity is completely impossible in Newtonian Mechanics.

49

Technology / Re: It's possible to build a full size car that gets 200 mpg

« on: 03/01/2015 02:12:38 »

It's not even theoretically possible that a carburettor, without changing your driving, would give you that range. Engines are about 20% efficient, and they would need to be about 100% efficient to get that range; but Carnot says no.

Still, internal combustion engined cars can achieve thousands of miles of range, but only at very average low speeds (like 15 mph) with special tyres, note that the engine isn't actually running most of the time, they start it, accelerate and then shut it down and coast.

50

General Science / Re: Are the words "natural" and "supernatural" actually meaningless?

« on: 15/05/2013 22:44:37 »

The word 'natural' is usually used to mean 'in accordance with well established physical laws' and supernatural is anything that is unproven.

If a claim of something supernatural was actually demonstrated, then it would (soon) become natural once somebody had worked out the principles involved; but NOT before.

So the term definitely means something.

51

General Science / Re: Do People have Free Will, or is the Concept Nothing But Illusion.

« on: 27/02/2012 11:21:28 »

The result is that you haven't modelled pain correctly.

Indeed, and no one else has either - it doesn't appear to be possible to model pain at all, so if you have ideas about how it can be done, I want to hear them.

I mean, a classic 'neural network' has no training system built into it, but humans clearly do have a training system, and pain is part of that system.

So a thing like pain is designed into a human or animal brain by evolution. It's a really strong sign that the animal is doing something very wrong, and should learn to avoid that in future. It's not just simply an input, like the colour red, it tells the other neurons that they need reprogramming.

I don't think learning is the immediate priority when pain is generated - it's about driving you to do something as quickly as possible to do something that might reduce or eliminate the pain.

Oh sure, I'm not saying that pain isn't a direct input to the nervous system, AS WELL, and I'm not saying that many of the immediate reactions aren't hard wired- if you burn your finger there's reflexes that pull your hand away as well as it being an input to your nervous system. And I'm sure there's one or more modules somewhere in the brain whose job it is to label something as 'bad' or 'good' which raise the stress levels and trigger flight-or-fight reactions.

Clearly there could be some learning associated with an event involving pain if it's a novel situation which could be avoided in future, but not at that immediate time.

Exactly and it has to correlate with the current situation that lead you there and cause downgrading of much of that activity. For example you might be in a particular geographical location, and that location will after that pain make you uneasy if you're there again. There will be a module in the brain that models physical location, and that location will end up being associated with pain by the learning process; which means that pain has had to directly adjust the neural weights associated with that activation. Presumably the whole time you're at a location, that location is associated with neuronal activity of some kind. Not like a GPS, but activation due to geographical features, mountain over there, tree over there, rock over there, kind of thing, and if you see that combination of features again, you'll get uneasy and run away.

What happens is that when you feel pain, your brain notices that and correlates neuronal activities that were happening around that time, and downvalues those things.

It's a VALUE of and for the neural network, it's not just an input, the neural network gets a hit of pain and downgrades everything a little, changes the weights between neurons. Which weights it chooses where in the brain, they have been selected by evolution, and it probably depends on what hurts, burning your finger is different from burning your foot is different from... there's doubtless chemical and electrical triggers that alter the weights.

Have you got this idea from somewhere that I could go to to read up on it more fully, because it sounds like an interesting idea, even if it doesn't relate directly to the business of pain driving action.

No, no the action itself is reflex, that's nothing immediately to do with learning.

I read something somewhere, somebody had found some structures that might act as part of a value system for the brain.

For the component that feels pain to be able to pass on knowledge of pain to the rest of the system, it would have to be a lot more complex than something that simply feels pain. What we'd need is something complex which collectively feels the pain and which understands that it is feeling the pain and which is able to articulate the fact that it is feeling the pain and which feels as if it is involved in the mechanism for responding to that pain. The last part of that is what makes people feel that they have free will (even though they don't), but the rest of it is problematic as it doesn't look as if it should be possible for something like that to exist at all.

That makes no sense at all. Something that feels pain and reacts to it, and learns to avoid pain is highly unlikely to involve anything we would normally describe as free will, it's going to be a very, very evolutionarily ancient process.

It isn't free will, but my point is that it feels as if it is because we feel as if we are something inside the machine that makes conscious decisions. If we were non-conscious machines like computers, no one would entertain the idea of free will at all, but adding consciousness into the system complifies things substantially, and no one has managed to get a handle on what consciousness is other than that it involves feelings of a multiplicity of different kinds, and these feelings have to be experienced by something and processed in some way so that they can have a role in the chain of causation. All of that is problematic.

It's just multiple things going on; pain generates stress reactions, reflexes, learning, negative feelings to the current situation, a desire for flight to get away; as well as good perception of many of them, all of these things are neuronally programmed; hard wired, but with learned inputs associated with the animals/humans value systems.