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Puzzled about direct current and charge (flux)

  1. Sep 3, 2012 #1
    This is a question that has kept me awake, trying to rationalise it:

    Current is rate-of-change-of-flux (or charge if you prefer, which is the same thing):
    i = dQ/dt
    Therefore, flux or charge is the time integral of the current.
    Q = ∫i dt

    Therefore, if you have a direct current, does this not imply that the flux/charge at a given point in the circuit keeps on growing indefinitely??
  2. jcsd
  3. Sep 3, 2012 #2

    Doc Al

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    Staff: Mentor

    No. The current in a circuit is the rate at which charge is flowing past a surface (or point).
  4. Sep 3, 2012 #3


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    Gold Member

    And how long could you keep this current flowing into a single point? The potential would pretty soon get so large that you couldn't continue. You are mis-interpreting the Maths.
  5. Sep 3, 2012 #4
    Ah, so my mistake was to say "the charge at a given point", when it should be "the charge that has passed a point", which of course can accumulate indefinitely!
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