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Thread: current

  1. #1 current 
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    hello.

    i have a problem with current (I)
    i know superficially what it is (electron movement through a cable)
    but what does it actually measure?
    is it the speed of electrons (aren't they moving at the speed of light?)
    or is it the amount of electrons moving past the measuring point?
    and voltage, is that the potential amount of electrons that can be put in motion?
    i think of voltage as a pump,
    and the electrons of current as pearls on a thread, that push eachother around.

    it makes more sense to me to think of voltage as the movement speed, or electron acceleration,
    and current as the amount of electrons moving at that speed.

    and please dont tell me that i really don't need to know this. i do or i'll go crazy. and try and keep it as close to physical reality as possible,
    describing actual electron movement, instead of comparing it to water, pumps and such.
    i don't care if the analogies are decent, i don't want them.
    if you don't know the answer, don't post in this thread.


    when you have eliminated the impossible, whatever remains, however improbable, must be the truth
    A.C Doyle
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  3. #2  
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    It measures the charge per unit of time passing through a conductor. If a wire is carrying 1 amp of current then there is 1 coulomb of charge (6E18 electrons) passing that point per second.
    The electrons do not move at the speed of light, but the effect of the current will appear at the other end of the wire almost instantaneously (near speed of light) when you close the switch.
    Voltage is also called electromotive force (emf) because it is the force that pushes the electrons around.


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  4. #3  
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    hmmm..
    thanks that explains a lot.
    so ampere is electrons/second.

    that means few electrons could be moving fast, and many electrons could be moving slow, and you'd still measure the same current.

    thanks!
    when you have eliminated the impossible, whatever remains, however improbable, must be the truth
    A.C Doyle
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  5. #4  
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    The electrons are not going at a constant speed. They are bumping into atoms of the conductor and bouncing around in all different directions. That's what makes the conductor resistive. The measured current is just an average of the overall movement.
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  6. #5  
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    I'm reading this page http://amasci.com/miscon/speed.html

    which says that current moves very slowly, approximately 3 inches per hour.
    when you have eliminated the impossible, whatever remains, however improbable, must be the truth
    A.C Doyle
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