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Why is charge a derived quantity

  1. Feb 4, 2013 #1
    Why is charge a derived quantity????
     
  2. jcsd
  3. Feb 4, 2013 #2
    Re: Charge!

    convention. Current was measured before charge.
     
  4. Feb 4, 2013 #3
    Re: Charge!

    There are seven base units from which all other units are derived.


    -meter (length)
    -kilogram (mass)
    -second (time)
    -ampere (electric current)
    -kelvin (temperature)
    -candela (luminous intensity)
    -mole (concentration of substance)

    Electric charge is measured in Coulombs, or Amperes seconds.
     
    Last edited: Feb 4, 2013
  5. Feb 4, 2013 #4

    jtbell

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    Staff: Mentor

    In SI, current is a fundamental unit (ampere) and charge is a derived unit (coulomb = ampere · second) for practical reasons. It's easier to implement the standard for current precisely, by measuring the force between two current-carrying wires, than it would be to implement a standard for charge precisely, involving something like measuring the force between two charges, or counting electrons.
     
  6. Feb 4, 2013 #5

    AlephZero

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    Science Advisor
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    Re: Charge!

    Ampere seconds, not amperes per second.
     
  7. Feb 4, 2013 #6
    Re: Charge!

    My apologies.
    Edited and corrected.
     
  8. Feb 4, 2013 #7
    No prob. Thanks for that. Really cleared it up
     
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