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Homework Help: LC Circuits

  1. Nov 21, 2013 #1


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    I'm having a difficult time finding any information in regards to LC circuits.

    The total energy in an circuit is 5.0*10^-6 J. If C= 15 microfarads, what is the charge
    on the capacitor? the ans is 12 microC

    An circuit has an inductance of 15 mH and a capacitance of 10 µF. At one instant
    the charge on the capacitor is 25 µC. At that instant the current is changing at what rate?

    ans : 170 A/s

    Again, I am unable to find the formula/information to solve these equations. Can someone please tell me what I am missing. I know the inductance equations (RLC) , but I don't see any in our book that contain just LC.

    Thank you.
  2. jcsd
  3. Nov 21, 2013 #2


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    Staff: Mentor

    What is the equation for the energy stored on a capacitor in terms of the capacitance and voltage?

    Write the differential equations for a series LC circuit. Does that help you to get to the answer?
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