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Electricity Doesn't Flow Through Wire

I can see how a conductor gets hot through the vibration, rather than the flow, of electrons. But I still don't see how the energy flow is through the surrounding fields, but only hurts people if they touch the conductor. That bit is weird.

Which brings me to a related topic which I think I've raised before, but for which I don't recall a satisfactory answer... To whit..

According to my 1965 Cambridge Board (The hardest obviously...) O Level Physics, plus my general layman's science knowledge.. 'permanent' magnets work by having all of their atoms/molecules aligned in such a way that they act, effectively as a 'lens' for the lines of force in the Earth's magnetic field, focusing them in much the same way that an optical lens focuses light waves. So... what happens when you remove a permanent magnet from the Earth's magnetic field? You take it out into deep space for e.g. Assuming you haven't taken it into a replacement magnetic field, does it still act as a magnet? Mmmm? Mmmmm?

Of course I could be talking bollox. It's that time of night and it has been known.. although very rarely... :)
 
I can see how a conductor gets hot through the vibration, rather than the flow, of electrons. But I still don't see how the energy flow is through the surrounding fields, but only hurts people if they touch the conductor. That bit is weird.

Which brings me to a related topic which I think I've raised before, but for which I don't recall a satisfactory answer... To whit..

According to my 1965 Cambridge Board (The hardest obviously...) O Level Physics, plus my general layman's science knowledge.. 'permanent' magnets work by having all of their atoms/molecules aligned in such a way that they act, effectively as a 'lens' for the lines of force in the Earth's magnetic field, focusing them in much the same way that an optical lens focuses light waves. So... what happens when you remove a permanent magnet from the Earth's magnetic field? You take it out into deep space for e.g. Assuming you haven't taken it into a replacement magnetic field, does it still act as a magnet? Mmmm? Mmmmm?

Of course I could be talking bollox. It's that time of night and it has been known.. although very rarely... :)
Well, I've got 1968 Oxford and Cambridge Joint Board A level physics, so obviously much harder than yours on all counts, and I don't remember any of that guff re permanent magnets. Is it true, I wonder?
 
Well, I've got 1968 Oxford and Cambridge Joint Board A level physics, so obviously much harder than yours on all counts, and I don't remember any of that guff re permanent magnets. Is it true, I wonder?

How would I know? I only got O level..although I can proudly claim that I never failed A level.. cheifly by the cunning device of not taking it...
Eitherway.. I'm looking to the intellectual PFM Gods of Physics for guidance in this matter.
 
P.S. I'm a bit miffed that nobody seems to recognise Reluctance as a genuine electro/magnetic term. I'm a relative ignoramus and I've heard of it.. Try to keep up chaps!
 
Mull,

Eitherway.. I'm looking to the intellectual PFM Gods of Physics for guidance in this matter.

You uttered the words that conjures the pfm physics demon! Prepare yourself to be on the receiving end of a lecture most likely tomorrow.

Joe
 
So experiment proved theory?
The term "proved" has to be properly qualified:
  • A scientific hypothesis is a reasonable model to explain something in nature, and can be used to predict behavior.
  • An experiment can be used to test whether that prediction holds up. If enough experimental evidence is amassed, then a hypothesis eventually becomes a theory.
  • If experiments show that a theory doesn't predict all behaviors, then the theory is disproven, perhaps replaced by a better one.
Case in point: Newton's theory of gravity held up for a long time, but it was supplanted by Einstein's. Experiments continue to prove that Einstein's theory is better at predicting observed behavior.
 
So experiment proved theory?
Well sort of. As @Mike Hanson writes, when testing a theory / hypothesis / conjecture (depending on how well an "educated guess" is known to work at predicting reality) mostly you are looking for a contradiction that disproves it - either generally or in a particular circumstance that establishes some limit on where it works.

That's the reason behind the somewhat convoluted "not disproved" double-negative language you were quite naturally wondering about in the post you commented on and in my post assuming what that one referred to. This makes me think that perhaps in a forum I ought to drop "correctness" for the sake of clarity.
 
The problem with theoretical physics is that experiment and proof are always lacking - if they were not, it would not be "theoretical".

Nope, that's not what the term means.

Theoretical physicists start with a mathematical model and experimental results to formulate new models which are a closer match for experimental results. They then typically design experiments which would show the differences between the previous models predictions and their own, and by running that experiment, demonstrate that their model is superior. Einstein and Hawking would be fine examples of theoretical physicists. Of course there are plenty of theories that the experiments haven't (yet) been run, either due to lack of ability to build such an experiment, or the physical impossibility of doing it, but that shouldn't detract from the large amount of knowledge which is obtained this way. A recent example of really great work would be the detection of gravitational waves by LIGO and Virgo as these were built to detect a theoretical concept which hadn't previously been observed.

By contrast experimental physics is where you build the experiment first, to probe for strange stuff that you then try and formulate a theory for. Building telescopes would be a great example - you build the tool to make the observations to then theorise about what you're looking at. CERN would also be an obvious large scale effort, as are the efforts to build fusion reactors, and anything that is chipping away at making better machines, say, in the field of microprocessor manufacture, optics etc. It's basically the practical end of the subject which yields incremental improvements to theories and methods, but it does also involve huge jumps at times.

The distinction is somewhat artificial, but it's useful as there are plenty of physicists who you would rather keep behind desks working on paper than building stuff. There are exceptions, the Feynmans of this world, but normally excelling at one would preclude the other.
 
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Well it sounds like you have enlightened teachers. I think that studying the history of science should be compulsory for all scientists, as you go from thinking that our forebears were cretinous fools for believing that there are four elements (earth, air, fire, water), there's an aether, or that the world is flat etc etc, to realising you're on a continuum, and that future generations will have the same low opinion about us and our current theories and understanding. 'They used to believe that electricity travelled in what they called electromagnetic fields in the space around the wire, ha ha ha' etc
I don't think any of my scientific predecessors were cretins. They didn't get it all right, but they built on what had gone before. Euclid came up with his model of geometry, OK it only works on a flat plane but it certainly works. The ancient Egyptians (I think) had Pi down as 3 from practical measurements. One ancient civilisation even had it at 4. Were they idiots? No, they were developing the model and building on it. In the same way *some* of modern science will be discredited but the vast majority of it is sound and will remain so. Ohms Law will remain true EVEN IF someone comes up with a special case where it doesn't. At that point nobody will throw away every electronics text and start again, they'll simply add an addendum that says (notwithstanding the Smith -Johnson anomaly of 2087). Even the much-quoted existence of wave particle duality does not discredit the science of how waves work and how particles do. Scientists learn from the past, question it and build upon it. They might have to remove bits of it that were a dead end, but they don't demolish the entire edifice and start again. In this they are like the cathedrals built in the Middle Ages, the stonemasons of the time didn't understand civil engineering and bits of their constructions don't quite work, but we don't tear them down. We recognise their limitations and build on them. The basics that still work, and the necessary modifications, such as the mini spires atop buttress attachment points that are needed to stop the wall being pushed off vertical, remain.
 
Not certain that all the cable charlatans are able to understand such phenomena. I may be wrong though.
 
Atoms are almost entirely empty space so in theory we would expect to pass through solid walls and fall through floors but we don't. This behaviour can be explained using the Pauli Exclusion Principle and the uncertainty principle. This is an example of modern physics.

The universe is a strange place and I am beginning to think that everything that we observe in this physical Universe are all made from incredibly small vibrating waves.

DV

The empty space isn't empty. It holds the Dirac 'foam' and represents the surface below which lurks the zero point energy that pops up virtual particles, etc. 8-]

And given Mach's Principle, I suspect that the expansion behaviour we see (and the above) are due to the entire universe *rotating* about its time-axis. 8->
 
I always thought that electrons "flowed" at varying depth around the skin of the conductor and not necessarily via the centre.

Yes, If you set up a sinewave current though a wire the electrons just under the surface of the wire get driven to move back and forth. But only move a tiny way and keep bumning into each other. Like stirring treacle. And just like stirring treacle, the energy lost warms them up - i.e. movements get randomised.

The vast bulk of any power carried goes along *outside* the metal. The wires act as a waveguide.

So when you turn on a light it comes on essentially instantly. But if it needed to have individual electrons move from switch to lamp you'd have to go and have a cup of tea or coffee as you waited for the lamp to light up. None of them go very far in practice before they bump into an atom or other electron and forget where they were going.
 
You may need to know something about how some types of cartridge work, or transformers to geddit.

Yebbut.. I don't need to 'geddit'. I just need to drop it into the conversation at strategic points, to give the entirely false impression that I know something...;)

Many years ago, in a lengthy and completely barmy letter to Hi Fi World.. I think I mentioned inductance, impedance, capacitance and even reluctance. But I added in a parameter of my own devising, which I termed 'repugnance'. They published..which brings into question who is the more barmy.. me or them? :D
 


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