• This topic has 71 replies, 40 voices, and was last updated 8 years ago by andyl.
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  • Electricity – it just struck me…
  • GrahamS
    Full Member

    Incidentally I had the same realisation as the OP and decided it was about time I learnt the secrets of electrickery and taught myself some electronics.

    There are lots and lots of good YouTube videos about the very basics, but even something as apparently simple as a capacitor appears to work by witchcraft and soon you learn there are all kinds of other mystical properties and considerations you didn’t know about (e.g. impedance, inductive reactance and capacitive reactance).

    I can now plug a few chips and components together on a breadboard but I am still constantly surprised and befuddled with what comes out 😀

    bencooper
    Free Member

    Just don’t ask me to explain quantum tunneling

    Can be summed up as “Electrons don’t know where they are” 😉

    TheBrick
    Free Member

    but they can know within a probaility of where they should be…

    At least I think that it is it. Probably.

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    andytherocketeer
    Full Member

    capacitors are only witchcraft if you think in the DC domain.

    but they can be well fun for making things go bang! 😈

    Rockplough
    Free Member

    Well let me see, in simple terms without Googling anything.

    It is the activity of electrons in conductors, and a bit like how objects always want to lose potential energy (fall), electricity has potential (which we put in via power stations etc) but always wants to go to earth (zero potential) and we can harness the resulting work to power things.

    In a broader sense it’s inextricably linked with magnetism, light (light itself not light bulbs), and governs the fundamental properties and behaviour of matter.

    slowoldman
    Full Member

    Electrickery. Telling Bone. ‘Tis all a mystery.

    Cougar
    Full Member

    True story,

    My OH asked if we could take a battery off a bike and take it upstairs to charge. I replied, “potentially.”

    Then I spent the next ten minutes giggling quietly to myself whilst she looked at me shaking her head.

    Northwind
    Full Member

    Rockplough – Member

    In a broader sense it’s inextricably linked with magnetism

    ****ing magnets? How do they work?

    GrahamS
    Full Member

    Found the explanation that messed with my head:

    “Conventional current is wrong” …is actually wrong.

    It’s wrong because it’s based on the widespread misconception “all electric currents are electron flows.”

    Why would science+engineering use conventional current? Because protons flow, of course. For example in battery acid, in proton conductors in fuel cells, and in electroplating tanks. Also, currents made of positive ions can flow in oceans, dirt, human bodies, alkaline battery electrolyte, and plasmas during sparks, neon signs, fluroescent tubes. Positive ions are atoms with more protons than electrons, while negative ions have more electrons than protons (and positive hydrogen ions? They’re called “protons.” Duh.) Positive ion currents are usually accompanied by negative ions flowing backwards at the same time in the same conductor (so, which way is the “true” current in an electrolyte, if it’s actually made of two opposite populations of charge flowing in two opposite directions?)

    In all of the above, we simplify things by pretending that negative charge, if flowing backwards, is the same thing as positive charge flowing forwards. Then we add the pos-charge and neg-charge currents together. Our clamp-on ammeters, they directly measure conventional current. An ampere flowing in the ground or in a human arm may be composed of equal and opposite ion flows (with no electron flows,) but your DVM amps-setting will report it as one ampere of conventional current.

    Where did the misconception arise? Easy: electric currents in metals are electron flows, same as in vacuum tubes. Some grade-school and tech-school authors decided to teach that, since currents in metal wires are electrons, that means that all currents everywhere are electrons. Just ignore the currents in glowing gas, liquids, human bodies, earth, and battery electrolyte. Screw up the minds of the poor chemistry students even before they take their first chem class.

    When we get right down to it, saying “conventional current is wrong” …that’s STUPID, it’s a confusing misconception being spread by grade-school teachers, just like when they teach that “it’s not the volts that kills you, it’s the amps.” It does a great disservice to anyone who goes into science and engineering, where their professors have to spend time trying to remove the misconceptions that “all currents are really just electrons,” and “conventional current is wrong because positive charges cannot flow.”

    Electron-flow applies to solid metals, not solids. But conventional current isn’t “wrong” in the first place, since conventional current isn’t a flow of positive particles. Instead it’s a coverup; a simplification. Ammeters measure conventional current, they ignore the actual particle flows. Ammeters don’t care whether the current is positive sodium ions flowing one way, or negative chloride ions flowing backwards, so ammeters aren’t “wrong.” Instead they report a simplified concept, and they conceal the true direction/speed/makeup of the particle flows. If someone prefers reality, then they must abandon ammeters entirely, and instead use some sort of instrument which senses the separate particle populations and their separate drift velocities.

    All taken from the comments on this video, which I thought was a nice concise explanation till I read the comments!

    [video]https://www.youtube.com/watch?v=8gvJzrjwjds[/video]

    wombat
    Full Member

    Electricity is a force that is passed down copper cables by a process similar to squeezing an orange down the sleeve of a jumper.

    The contractions are so small as to be imperceptible to the human eye (or hand since you can’t feel them if you hold an insulated live cable).

    If you hold an uninsulated live cable the cable will think you’re a predator and will attempt to throw you off and will make a cracking noise to scare you.

    Cables have to be firmly clamped at the ends (inside a 13a plug for example) in order to give the “swallow” effect something to brace against. THis is why it doesn’t work as well if the connection is loose.

    HYH

    I am not an electrician

    Cougar
    Full Member

    Electron-flow applies to solid metals, not solids. But conventional current isn’t “wrong” in the first place, since conventional current isn’t a flow of positive particles. Instead it’s a coverup; a simplification. Ammeters measure conventional current, they ignore the actual particle flows. Ammeters don’t care whether the current is positive sodium ions flowing one way, or negative chloride ions flowing backwards, so ammeters aren’t “wrong.” Instead they report a simplified concept, and they conceal the true direction/speed/makeup of the particle flows. If someone prefers reality, then they must abandon ammeters entirely, and instead use some sort of instrument which senses the separate particle populations and their separate drift velocities.

    Did anyone else end up reading this in Jon Pertwee’s voice by the time they were halfway through it, or is it just me?

    bencooper
    Free Member

    Can we do the double slit experiment now? For total WTF it’s hard to beat:

    [video]https://www.youtube.com/watch?v=DfPeprQ7oGc[/video]

    Northwind
    Full Member

    I just use the water metaphor, it’s mostly pretty effective. Except for that time I accidentally connected 2 12V lives on my PC together and it went on fire- you don’t get that with plumbing.

    CountZero
    Full Member

    Next, a quick guide to Quarks, Strangeness, Charm and colour…
    Lolz at Cougar’s battery-charging joke!

    slowoldman
    Full Member

    No no. Not the double slit. That’s just…. aaaaaagh.

    jivehoneyjive
    Free Member

    It’s sparky stingy stuff that you can’t play with in the bath.

    Sometimes the sky makes it to keep us humble.

    Though it’s been around for ages, we haven’t been aware of it for long… what will we find next?

    funkynick
    Full Member

    It always seems to mess with peoples heads that in a copper wire an electron only travels at a few centimeters per hour, but the electricity is there as soon as you turn the switch on… so how do the electrons further up the wire know to start moving? ;o)

    Wally
    Full Member

    I teach electricity is like a mexican wave (get ready class for a huge mexican wave of shoves with the end child falling off their stool into the lamp) or the wire a tube full of glass marbles as electrons, the electron getting to the light is not the one leaving the battery. hence the very high speed.

    I also mention transparency is about a substance having no crystals or cell like structure to bounce the light around.

    Of course, this never comes up in exams – but everyone should know why the sky is blue, particularly if you teach in Rayleigh.

    IanMunro
    Free Member

    Have you thought about teaching it like this? 🙂
    [video]https://www.youtube.com/watch?v=snk3C4m44SY[/video]

    Wally
    Full Member

    A DIY step up and down transformer showing how the national grid works has caught out many a teacher. CLEAPSS is useful on this. Electricity is a very hard thing to teach, Flemming left hand rule? How on Earth does motion of a conductor with “free electrons” in a magnetic field induce a flow of electrons? When a particle acts like a wave and then changes back to a particle behaviour when you look at it, that’s odd and beyond me.

    esselgruntfuttock
    Free Member

    No idea what it is except it make the house a bit lighter than using candles (4)

    AND.. I leaned my bike against a fence last Saturday & when I tried to undo the skewer on the front wheel…….
    I’ll let you guess the next bit.

    maccruiskeen
    Full Member

    It tastes hurty

    igm
    Full Member

    I love how all the explanations are DC so far.

    AC electricity is really going to blow your mind – the current flows both ways but the power only flows one…

    PS you’re all trying too hard with visualising electrons and holes etc. they’re very small really and most of the time they move about randomly only generally drifting in the direction indicated by the current (conventional or otherwise).

    Spin
    Free Member

    Have you thought about teaching it like this?

    That’s brilliant. It’s like he knows the theory but not the commonsense stuff.

    Edit – had a look at his channel and it’s obviously a spoof. Still funny though.

    bencooper
    Free Member

    AC electricity is really going to blow your mind – the current flows both ways but the power only flows one…

    And if AC blows your mind, whatever you do don’t think too hard about three-phase 😀

    igm
    Full Member

    I looked at that 3 phase current stuff – as far as I can see it doesn’t add up to anything much.

    Cougar
    Full Member

    And if AC blows your mind, whatever you do don’t think too hard about three-phase

    I like to think I’m a geeky kind of guy, and three-phase properly baffles me.

    igm
    Full Member

    3^0.5

    bencooper
    Free Member

    I think of it like this:

    – DC is like pushing a car along the road

    – AC is like a single cylinder piston engine

    – 3-phase is like a Wankel rotary engine

    That’s probably a really bad analogy.

    TheBrick
    Free Member

    I read an interesting artical about some good theoretical and pratical experments to consider a 6 phase system for electrical pwoer distribution, it had some good advantages but the extra infistructure costs made it too expensive. Now with cheap highpowerd power mosfets and IGBTs we could loaclaly create 6 phase systems within sitautions where it would be advantagouse if the units to used it where made.

    igm
    Full Member

    Are you sure 6 phase wasn’t just centre tapped 3 phase?

    andyl
    Free Member

    Just don’t start asking yourself how some solids are transparent and other very similar ones aren’t. Or why where’s no transparent metals

    Having to explain this stuff to a curious 5-year-old is fun…

    Remember, you are just talking about transparency in the optical part of the spectrum. There is a whole load more head hurting stuff to think about when you go wider.

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