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Thread: Electric Theory

  1. #11
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    Quote Originally Posted by Coppersmith View Post
    Electricity is the movement of electrons.
    I equate electron movement in a conductor to a garden hose filled with marbles. Push one more into one end of the hose and one immediately pops out of the other end. Not the same marble, which would take a while, but the effect is instantaneous.
    Code references based on 2005 NEC
    Larry B. Fine
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  2. #12
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    Quote Originally Posted by GoldDigger View Post
    To the extent that an electric current is the result of moving electrical charges, those charges or their equivalent quantity of charge must return to the source to avoid a buildup of charge which would cause a voltage offset. That voltage offset would eventually be enough to stop current from flowing by opposing the force that is making them move in the first place.
    This is one of the weaknesses of the water analogy for electricity, in that people do not tend to immediately realize that water eventually returns to its source too, via evaporation, rainfall, and a host of other background processes.
    Hydraulic analogy is better then you may think. A hydraulic system does return the media to a reservoir and it eventually cycles through the system again instead of being replaced with something else.

    Kind of same thing as described here.

    Quote Originally Posted by Coppersmith View Post
    Electricity is the movement of electrons.

    Imagine a lake and a pump in that lake. The intake pipe is at one end of the lake and the output pipe is at the other. As the pump runs, water piles up on one side of the lake while a trough is created at the other. What happens? The water around the trough starts moving toward it to fill it in. As it moves it makes a smaller trough that other water fills in and so on. The lake water will flow from the high side to the low side until the lake is level again. Note that it's the nearby water atoms that are actually returning to the intake pipe (source), not the ones that were pumped to the far side of the lake. If you run the pump long enough they too may make it back, but not necessarily. They may just swirl around.

    The same is true for electrons. Electrons will flow back to the source, but not necessarily the same electrons. In a network of sources and loads (like the power grid) an individual electron could start at one source and flow back to a different source. Electrons will flow toward wherever there is a deficit of electrons until all the metal atoms have all their electrons back.
    I will say in an typical AC system derived by an isolation transformer the source is the secondary coil. No electrons flow between primary and secondary, just the energy carried by magnetic fields is transferred from primary to secondary.

  3. #13
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    But it doesn't have to return to the source "right away" right? We can take electrons from something, and push them elsewhere (I am thinking van degraff generator) but just only for so long until charge gets so high it jumps across or destroys whatever insulator we are using - correct or am I off base? If we had a good enough insulator, could we power something until we strip all the electrons from the source?
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  4. #14
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    Quote Originally Posted by LarryFine View Post
    I equate electron movement in a conductor to a garden hose filled with marbles. Push one more into one end of the hose and one immediately pops out of the other end. Not the same marble, which would take a while, but the effect is instantaneous.
    A common analogy possibly valid for DC. For AC, which we mostly use, the electrons don't go anywhere. They just jiggle back and forth a tiny little bit. There is no go and return in the way it is conventionally described.
    Si hoc legere scis nimium eruditionis habes.

  5. #15
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    Quote Originally Posted by electrofelon View Post
    But it doesn't have to return to the source "right away" right? We can take electrons from something, and push them elsewhere (I am thinking van degraff generator) but just only for so long until charge gets so high it jumps across or destroys whatever insulator we are using - correct or am I off base? If we had a good enough insulator, could we power something until we strip all the electrons from the source?
    Basically a gigantic static charge, it will seek whatever is at a lower potential. Like shuffling across carpet and touching a doorknob... the electrons are ripped from the carpet and do not go back to the source...amiright?
    Electricians do it until it Hertz!

  6. #16
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    Quote Originally Posted by JFletcher View Post
    Basically a gigantic static charge, it will seek whatever is at a lower potential. Like shuffling across carpet and touching a doorknob... the electrons are ripped from the carpet and do not go back to the source...amiright?
    With static charges the electrons taken from one object would eventually have to be replaced somehow I would think, otherwise the carpet in your example would eventually have a pretty high charge on it.

  7. #17
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    Quote Originally Posted by Besoeker View Post
    A common analogy possibly valid for DC. For AC, which we mostly use, the electrons don't go anywhere. They just jiggle back and forth a tiny little bit. There is no go and return in the way it is conventionally described.
    It is a valid analogy for each half cycle. The individual electrons don't move very much, but the instantaneous effect I described still moves at (almost) the speed of light.
    Code references based on 2005 NEC
    Larry B. Fine
    Master Electrician
    Electrical Contractor
    Richmond, VA

  8. #18
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    Quote Originally Posted by LarryFine View Post
    It is a valid analogy for each half cycle. The individual electrons don't move very much, but the instantaneous effect I described still moves at (almost) the speed of light.
    I don't disagree with near instantaneous effect. It doesn't long at all for you to realise you are being electrocuted.........
    Si hoc legere scis nimium eruditionis habes.

  9. #19
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    Quote Originally Posted by jaymiller View Post
    Why does electricity go back to its source?
    here ya go







    and remember, speed of light is c = 1/(e0m0)1/2

  10. #20
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    Quote Originally Posted by jaymiller View Post
    Why does electricity go back to its source?
    The simplistic answer to your question, as taught in K-12 school, is a closed circuit is required for current to flow from the source through a load and then back to the source.

    In reality the answer to your question is complex and can be quite concussing to understand.


    In a simple electric circuit, the electricity flows slowly in a complete circle, while the energy moves differently. The energy flows rapidly across the circuit, going from the source to the load but not returning. The energy does not follow the circular flow of electricity; electricity and electrical energy are two different things. No charges of electricity are gained or lost as the charges circulate within the wires, yet batteries create electrical energy from chemical energy, and light bulbs destroy[1] the electrical energy as they convert it into light. Electrical energy takes a rapid one-way path from battery to bulb and then leaves the circuit as light, while electricity flows slowly around (and around and around) a closed-loop path and none is lost.

    http://amasci.com/miscon/energ1.html


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