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Homework Help: Charge from current

  1. Aug 24, 2006 #1
    In this problem assume that current is linearly proportional to time. The intial condition at time 0 is 5A. At time 4 hours the current is 1A. What is the total charge that flows through this circuit?

    [tex] t_0=0 [/tex]
    [tex]i_0=5A [/tex]
    [tex]t_f=14400s [/tex]
    [tex]i_f=1A [/tex]

    [tex] \frac{i_f-i_0}{t_f-t_0} =\frac{-4A}{14400} [/tex]

    [tex] q=\int_{0}^{14400}(\frac{-1A}{3600}t+5)dt [/tex]

    [tex]q= \left[\frac{-1}{7200}t^2+5t\right]_{0}^{14400} [/tex]

    [tex]q= 43200C[/tex]

    That seems like a whole lot of charge. I know it is a long period of time. Can anyone see anything wrong with this?
    Last edited: Aug 24, 2006
  2. jcsd
  3. Aug 24, 2006 #2


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    1A is a very large current too. It looks fine to me.
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