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-   -   Capacitors (https://www.askmehelpdesk.com/showthread.php?t=15442)

  • Nov 29, 2005, 12:23 PM
    fizixx
    Capacitors
    Hello all, I have a capacitor problem that I can't seem to get a handle on. Maybe someone out there has some ideas.

    Ok... you have an AC source. It provides 25V (rms) with frequency of 580 Hz.

    There is a capacitor connected across its terminals. When a second cap. Is connected in parallel to the first one, the source current increases by 0.23 A.

    The object of the game here is to find the capacitance of the second cap. I'm just not seeing something about this problem, so I thought I'd post for some ideas.

    Thank you ***

    Fiz~
  • Nov 30, 2005, 07:07 AM
    colbtech
    Hi Fiz

    Bear in mind I had to do this sort of stuff 30 odd years ago, so I may be a little off, (those better educated, feel free to point out the errors)

    If this was a single cap then V=IR where V=25, I=0.23

    so R= 108.7, simple enough

    I think that now you have a resistance that you can use this as the reactance of the cap? So using:

    Xc = 1 / 2*PI*f*C

    where Xc = 108.7
    Pi = 3.14
    f = 580
    C = ?

    so

    C = 1 / 2*3.14*580*108.7

    C = 2.52uF

    However I don't think that this is the answer as you already have a capacitor in circuit.

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