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I Electrical charge, current definitions

  1. Sep 24, 2016 #1
    What is electrical charge?
    is it a measure of the abundance of electrons within a system?

    Current is defined as the amount of charge flowing between any two points in a system over a given period of time, correct?

    but what is elctrical charge if possible to define it better/further. I am also confused as to how many types of charge there exist, our professer said neutral electric charge is also one type apart from positive and negative! is this correct?

    I know that we dont know why there exists only negative and positive cahrges, and its hard to define what charge is but perhaps someone can explain in a better way, and is "neutral electric charge" a thing?

    thanks for your time!
     
  2. jcsd
  3. Sep 24, 2016 #2

    Nugatory

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    We made observations and did experiments to discover how the universe behaves, and we discovered is that there is something that is conserved, that comes in two flavors (which we arbitrarily label positive and negative), that like repels and unlike attracts, and that causes a force that obeys Coulomb's law. Now we need a name for that thing, and for historical reasons the name is "electrical charge".

    If something is attracted to a negatively charged surface we say that it has a positive charge, and if something is repelled by a negatively charged surface we say that it is has a positive negative charge. So what do we say about something that is neither attracted nor repelled by a charged surface?

    We could say that its electric charge is zero, or that it has no charge, or that it is neither positive nor negative.... Or we could say "neutral".
     
    Last edited: Sep 24, 2016
  4. Sep 24, 2016 #3

    Nugatory

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    Staff: Mentor

    We made observations and did experiments to discover how the universe behaves, and we discovered is that there is something that is conserved, that comes in two flavors (which we arbitrarily label positive and negative), that like repels and unlike attracts, and that causes a force that obeys Coulomb's law. Now we need a name for that thing, and for historical reasons the name is "electrical charge".

    If something is attracted to a negatively charged surface we say that it has a positive charge, and if something is repelled by a negatively charged surface we say that it is has a positive charge. So what do we say about something that is neither attracted nor repelled by a charged surface?

    We could say that its electric charge is zero, or that it has no charge, or that it is neither positive nor negative.... Or we could say "neutral".
     
  5. Sep 24, 2016 #4

    sophiecentaur

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    I think I liked it more the second time around. :wink:
     
  6. Sep 24, 2016 #5
    its alright, anyone taking their time out to help me gets my likes...no matter how many replicated posts :P
    I also think Mr Nugatory means if something is repelled by a positively charged surface it is positively charged!
     
  7. Sep 24, 2016 #6

    sophiecentaur

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    Yes. That is the convention we have decided upon - toss of a coin which way round it turned out.
     
  8. Sep 24, 2016 #7

    Nugatory

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    I've left the duplicate post up because everyone seems to be having so much fun with it.... And yes, of course I meant negative repels negative, positve repels positive, and negative and positive attract one another.... A hazard of typing too fast...
     
  9. Sep 24, 2016 #8
    Are you positive about that?
     
  10. Sep 25, 2016 #9

    David Lewis

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    Surplus/deficit of electrons is also an acceptable working picture.
    The generic definition is charge in motion. In the particular sense, current is the amount of charge moving past a point divided by time (I=Q/t).
     
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