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Why is a charge a scalar?

  1. Aug 14, 2014 #1
    Why is a charge from say an electron a scalar. It has a constant magnitude, and it has a direction.
     
  2. jcsd
  3. Aug 14, 2014 #2

    Vanadium 50

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    In what direction do you think it points?
     
  4. Aug 14, 2014 #3

    haruspex

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    Having a sign (+/-) is not the same as having direction unless you're looking at a 1-dimensional space.
     
  5. Aug 15, 2014 #4

    ShayanJ

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    The +/- convention, is only a proper and easy to use convention!!!
    Its OK to say that the two kinds of charges are black/white, fool/wise, fat/thin and any other pair of opposite nouns. The only problem is finding a way so that mathematically opposites attract and likes repel, and that's easiest when we use +/- convention, so we use it! There is nothing about direction here!
     
    Last edited: Aug 15, 2014
  6. Aug 15, 2014 #5

    haruspex

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    No, it's a bit more than a convention. You can add charges, allowing charges of opposing signs to cancel appropriately. That's a genuine mathematical interpretation of the sign.
     
  7. Aug 15, 2014 #6

    ShayanJ

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    You can as well say a fool and a wise combined, make an ordinary person. Its just that the +/- convention needs no such additional weird construction.
    I should add that the important role of mathematics in physics, makes the +/- convention also the most natural one, in addition to being an easy and proper one.
     
    Last edited: Aug 15, 2014
  8. Aug 15, 2014 #7

    D H

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    I suspect shangriphysics is using a dictionary definition of "scalar", such as "scalar - noun. (Mathematics, Physics). A quantity possessing only magnitude." (Source: http://dictionary.reference.com/browse/scalar).

    In physics (and this is a physics question), charge is a scalar rather than a vector or a tensor. In fact, it's all three; a scalar can be viewed as a one dimensional vector or a zeroth order tensor. However, we usually don't call one dimensional vectors "vectors". We call them scalars.
     
  9. Aug 15, 2014 #8

    ShayanJ

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    I don't think that's correct because it means charge is something like a one dimensional position variable. But that's not true!
    The +/- convention for electric charge is different from the +/- associated to different parts of the real line!
     
  10. Aug 15, 2014 #9

    D H

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    Ignoring that charge is quantized, charge is exactly "something like a one dimensional position variable".
     
  11. Aug 15, 2014 #10
    Oh, I had this same question. This makes more sense now.
     
  12. Aug 15, 2014 #11
    Thanks everyone for all your help! This is much clearer now to me!
     
  13. Aug 16, 2014 #12
    Now everything makes sense, I used to think (with similar reasoning) why energy can't be a vector.

    Thanks, man!
     
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