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Number of Coulombs question

  1. Aug 25, 2011 #1
    1. The problem statement, all variables and given/known data

    Given a 15A breaker, what is the max number of coulombs that can flow through before the breaker trips?

    2. Relevant equations

    i = dq/dt
    A = C/s

    3. The attempt at a solution

    No time value is given so I can't integrate dq = i dt from any limits.

    Is the right thing to just say it's 15 coulombs if we assume that the breaker will trip in a second?

  2. jcsd
  3. Aug 25, 2011 #2


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    Homework Helper

    I think you need a time reference. If 1 Coulomb went through in a billionth of a second that should trip it?
  4. Aug 25, 2011 #3


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    Staff: Mentor

    The question is not well posed. Surely, the current can flow indefinitely as long as it doesn't ever exceed the breaker's rating, thus the maximum coulombs would be indefinite.

    Now, if the question wanted to know the maximum number of coulombs per second, that would be a horse of different color!
  5. Aug 25, 2011 #4


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    Staff Emeritus
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    Gold Member

    If the current is less than (or equal to) 15 A, then the circuit breaker shouldn't trip at all. The number of coulombs that can flow through the circuit breaker is limited only by the amount of time the current flows.
  6. Aug 25, 2011 #5
    There is no time reference, which is why I'm pulling my hair out. I'll disregard this one. Thanks everyone.
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