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Homework Help: Capacitance calulation

  1. Apr 13, 2013 #1
    1. The problem statement, all variables and given/known data

    Trying to calculate capacitance on an LC circuit

    2. Relevant equations

    L = 1.0H (solenoid inductance)
    i = 3.0 Ma (current in circuit)
    Q = 30μC (charge on capacitor)
    E = 4.5μJ (energy in oscillations)

    3. The attempt at a solution

    All i'm after is an equation for capacitance that i can use with the given information
    I know that V=IR and I=Q/T and C=Q/V but none of these tie in what i'm trying to achieve.
    Any help would be great.
  2. jcsd
  3. Apr 13, 2013 #2
    Energy in oscillations means what??
  4. Apr 13, 2013 #3
    Energy stored in the oscillations of the solenoid.
  5. Apr 13, 2013 #4
    Which is 0.5 Li2 or something else...do u know the expression for the energy...if i am wrong.
  6. Apr 13, 2013 #5
    Sorry you've lost me
  7. Apr 13, 2013 #6
    I didn't get you....
  8. Apr 13, 2013 #7


    User Avatar

    Staff: Mentor

    Are these "Relevant Equations" for i,Q,E maximal values, or values at some particular instant of time?

    Can you write the expressions for the energy stored in an inductor given the current flowing through it? How about the energy stored in a capacitor given the charge stored on it?
  9. Apr 14, 2013 #8
    Vcap (t) = (q(t))/C
    Eel = ½ CV2
    EMF = Vbat – L (di(t))/dt
    f = 1/(2π√LC)
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